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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Main SSAM/SSH controller structure and functionality.
  *
  * Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
  */
 
 #include <linux/acpi.h>
 #include <linux/atomic.h>
 #include <linux/completion.h>
 #include <linux/gpio/consumer.h>
 #include <linux/interrupt.h>
 #include <linux/kref.h>
 #include <linux/limits.h>
 #include <linux/list.h>
 #include <linux/lockdep.h>
 #include <linux/mutex.h>
 #include <linux/rculist.h>
 #include <linux/rbtree.h>
 #include <linux/rwsem.h>
 #include <linux/serdev.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/srcu.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
 
 #include <linux/surface_aggregator/controller.h>
 #include <linux/surface_aggregator/serial_hub.h>
 
 #include "controller.h"
 #include "ssh_msgb.h"
 #include "ssh_request_layer.h"
 
 #include "trace.h"
 
 
 /* -- Safe counters. -------------------------------------------------------- */
 
 /**
  * ssh_seq_reset() - Reset/initialize sequence ID counter.
  * @c: The counter to reset.
  */
 static void ssh_seq_reset(struct ssh_seq_counter *c)
 {
     WRITE_ONCE(c->value, 0);
 }
 
 /**
  * ssh_seq_next() - Get next sequence ID.
  * @c: The counter providing the sequence IDs.
  *
  * Return: Returns the next sequence ID of the counter.
  */
 static u8 ssh_seq_next(struct ssh_seq_counter *c)
 {
     u8 old = READ_ONCE(c->value);
     u8 new = old + 1;
     u8 ret;
 
     while (unlikely((ret = cmpxchg(&c->value, old, new)) != old)) {
         old = ret;
         new = old + 1;
     }
 
     return old;
 }
 
 /**
  * ssh_rqid_reset() - Reset/initialize request ID counter.
  * @c: The counter to reset.
  */
 static void ssh_rqid_reset(struct ssh_rqid_counter *c)
 {
     WRITE_ONCE(c->value, 0);
 }
 
 /**
  * ssh_rqid_next() - Get next request ID.
  * @c: The counter providing the request IDs.
  *
  * Return: Returns the next request ID of the counter, skipping any reserved
  * request IDs.
  */
 static u16 ssh_rqid_next(struct ssh_rqid_counter *c)
 {
     u16 old = READ_ONCE(c->value);
     u16 new = ssh_rqid_next_valid(old);
     u16 ret;
 
     while (unlikely((ret = cmpxchg(&c->value, old, new)) != old)) {
         old = ret;
         new = ssh_rqid_next_valid(old);
     }
 
     return old;
 }
 
 
 /* -- Event notifier/callbacks. --------------------------------------------- */
 /*
  * The notifier system is based on linux/notifier.h, specifically the SRCU
  * implementation. The difference to that is, that some bits of the notifier
  * call return value can be tracked across multiple calls. This is done so
  * that handling of events can be tracked and a warning can be issued in case
  * an event goes unhandled. The idea of that warning is that it should help
  * discover and identify new/currently unimplemented features.
  */
 
 /**
  * ssam_event_matches_notifier() - Test if an event matches a notifier.
  * @n: The event notifier to test against.
  * @event: The event to test.
  *
  * Return: Returns %true if the given event matches the given notifier
  * according to the rules set in the notifier's event mask, %false otherwise.
  */
 static bool ssam_event_matches_notifier(const struct ssam_event_notifier *n,
                     const struct ssam_event *event)
 {
     bool match = n->event.id.target_category == event->target_category;
 
     if (n->event.mask & SSAM_EVENT_MASK_TARGET)
         match &= n->event.reg.target_id == event->target_id;
 
     if (n->event.mask & SSAM_EVENT_MASK_INSTANCE)
         match &= n->event.id.instance == event->instance_id;
 
     return match;
 }
 
 /**
  * ssam_nfblk_call_chain() - Call event notifier callbacks of the given chain.
  * @nh:    The notifier head for which the notifier callbacks should be called.
  * @event: The event data provided to the callbacks.
  *
  * Call all registered notifier callbacks in order of their priority until
  * either no notifier is left or a notifier returns a value with the
  * %SSAM_NOTIF_STOP bit set. Note that this bit is automatically set via
  * ssam_notifier_from_errno() on any non-zero error value.
  *
  * Return: Returns the notifier status value, which contains the notifier
  * status bits (%SSAM_NOTIF_HANDLED and %SSAM_NOTIF_STOP) as well as a
  * potential error value returned from the last executed notifier callback.
  * Use ssam_notifier_to_errno() to convert this value to the original error
  * value.
  */
 static int ssam_nfblk_call_chain(struct ssam_nf_head *nh, struct ssam_event *event)
 {
     struct ssam_event_notifier *nf;
     int ret = 0, idx;
 
     idx = srcu_read_lock(&nh->srcu);
 
     list_for_each_entry_rcu(nf, &nh->head, base.node,
                 srcu_read_lock_held(&nh->srcu)) {
         if (ssam_event_matches_notifier(nf, event)) {
             ret = (ret & SSAM_NOTIF_STATE_MASK) | nf->base.fn(nf, event);
             if (ret & SSAM_NOTIF_STOP)
                 break;
         }
     }
 
     srcu_read_unlock(&nh->srcu, idx);
     return ret;
 }
 
 /**
  * ssam_nfblk_insert() - Insert a new notifier block into the given notifier
  * list.
  * @nh: The notifier head into which the block should be inserted.
  * @nb: The notifier block to add.
  *
  * Note: This function must be synchronized by the caller with respect to other
  * insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
  *
  * Return: Returns zero on success, %-EEXIST if the notifier block has already
  * been registered.
  */
 static int ssam_nfblk_insert(struct ssam_nf_head *nh, struct ssam_notifier_block *nb)
 {
     struct ssam_notifier_block *p;
     struct list_head *h;
 
     /* Runs under lock, no need for RCU variant. */
     list_for_each(h, &nh->head) {
         p = list_entry(h, struct ssam_notifier_block, node);
 
         if (unlikely(p == nb)) {
             WARN(1, "double register detected");
             return -EEXIST;
         }
 
         if (nb->priority > p->priority)
             break;
     }
 
     list_add_tail_rcu(&nb->node, h);
     return 0;
 }
 
 /**
  * ssam_nfblk_find() - Check if a notifier block is registered on the given
  * notifier head.
  * list.
  * @nh: The notifier head on which to search.
  * @nb: The notifier block to search for.
  *
  * Note: This function must be synchronized by the caller with respect to other
  * insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
  *
  * Return: Returns true if the given notifier block is registered on the given
  * notifier head, false otherwise.
  */
 static bool ssam_nfblk_find(struct ssam_nf_head *nh, struct ssam_notifier_block *nb)
 {
     struct ssam_notifier_block *p;
 
     /* Runs under lock, no need for RCU variant. */
     list_for_each_entry(p, &nh->head, node) {
         if (p == nb)
             return true;
     }
 
     return false;
 }
 
 /**
  * ssam_nfblk_remove() - Remove a notifier block from its notifier list.
  * @nb: The notifier block to be removed.
  *
  * Note: This function must be synchronized by the caller with respect to
  * other insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
  * Furthermore, the caller _must_ ensure SRCU synchronization by calling
  * synchronize_srcu() with ``nh->srcu`` after leaving the critical section, to
  * ensure that the removed notifier block is not in use any more.
  */
 static void ssam_nfblk_remove(struct ssam_notifier_block *nb)
 {
     list_del_rcu(&nb->node);
 }
 
 /**
  * ssam_nf_head_init() - Initialize the given notifier head.
  * @nh: The notifier head to initialize.
  */
 static int ssam_nf_head_init(struct ssam_nf_head *nh)
 {
     int status;
 
     status = init_srcu_struct(&nh->srcu);
     if (status)
         return status;
 
     INIT_LIST_HEAD(&nh->head);
     return 0;
 }
 
 /**
  * ssam_nf_head_destroy() - Deinitialize the given notifier head.
  * @nh: The notifier head to deinitialize.
  */
 static void ssam_nf_head_destroy(struct ssam_nf_head *nh)
 {
     cleanup_srcu_struct(&nh->srcu);
 }
 
 
 /* -- Event/notification registry. ------------------------------------------ */
 
 /**
  * struct ssam_nf_refcount_key - Key used for event activation reference
  * counting.
  * @reg: The registry via which the event is enabled/disabled.
  * @id:  The ID uniquely describing the event.
  */
 struct ssam_nf_refcount_key {
     struct ssam_event_registry reg;
     struct ssam_event_id id;
 };
 
 /**
  * struct ssam_nf_refcount_entry - RB-tree entry for reference counting event
  * activations.
  * @node:     The node of this entry in the rb-tree.
  * @key:      The key of the event.
  * @refcount: The reference-count of the event.
  * @flags:    The flags used when enabling the event.
  */
 struct ssam_nf_refcount_entry {
     struct rb_node node;
     struct ssam_nf_refcount_key key;
     int refcount;
     u8 flags;
 };
 
 /**
  * ssam_nf_refcount_inc() - Increment reference-/activation-count of the given
  * event.
  * @nf:  The notifier system reference.
  * @reg: The registry used to enable/disable the event.
  * @id:  The event ID.
  *
  * Increments the reference-/activation-count associated with the specified
  * event type/ID, allocating a new entry for this event ID if necessary. A
  * newly allocated entry will have a refcount of one.
  *
  * Note: ``nf->lock`` must be held when calling this function.
  *
  * Return: Returns the refcount entry on success. Returns an error pointer
  * with %-ENOSPC if there have already been %INT_MAX events of the specified
  * ID and type registered, or %-ENOMEM if the entry could not be allocated.
  */
 static struct ssam_nf_refcount_entry *
 ssam_nf_refcount_inc(struct ssam_nf *nf, struct ssam_event_registry reg,
              struct ssam_event_id id)
 {
     struct ssam_nf_refcount_entry *entry;
     struct ssam_nf_refcount_key key;
     struct rb_node **link = &nf->refcount.rb_node;
     struct rb_node *parent = NULL;
     int cmp;
 
     lockdep_assert_held(&nf->lock);
 
     key.reg = reg;
     key.id = id;
 
     while (*link) {
         entry = rb_entry(*link, struct ssam_nf_refcount_entry, node);
         parent = *link;
 
         cmp = memcmp(&key, &entry->key, sizeof(key));
         if (cmp < 0) {
             link = &(*link)->rb_left;
         } else if (cmp > 0) {
             link = &(*link)->rb_right;
         } else if (entry->refcount < INT_MAX) {
             entry->refcount++;
             return entry;
         } else {
             WARN_ON(1);
             return ERR_PTR(-ENOSPC);
         }
     }
 
     entry = kzalloc(sizeof(*entry), GFP_KERNEL);
     if (!entry)
         return ERR_PTR(-ENOMEM);
 
     entry->key = key;
     entry->refcount = 1;
 
     rb_link_node(&entry->node, parent, link);
     rb_insert_color(&entry->node, &nf->refcount);
 
     return entry;
 }
 
 /**
  * ssam_nf_refcount_dec() - Decrement reference-/activation-count of the given
  * event.
  * @nf:  The notifier system reference.
  * @reg: The registry used to enable/disable the event.
  * @id:  The event ID.
  *
  * Decrements the reference-/activation-count of the specified event,
  * returning its entry. If the returned entry has a refcount of zero, the
  * caller is responsible for freeing it using kfree().
  *
  * Note: ``nf->lock`` must be held when calling this function.
  *
  * Return: Returns the refcount entry on success or %NULL if the entry has not
  * been found.
  */
 static struct ssam_nf_refcount_entry *
 ssam_nf_refcount_dec(struct ssam_nf *nf, struct ssam_event_registry reg,
              struct ssam_event_id id)
 {
     struct ssam_nf_refcount_entry *entry;
     struct ssam_nf_refcount_key key;
     struct rb_node *node = nf->refcount.rb_node;
     int cmp;
 
     lockdep_assert_held(&nf->lock);
 
     key.reg = reg;
     key.id = id;
 
     while (node) {
         entry = rb_entry(node, struct ssam_nf_refcount_entry, node);
 
         cmp = memcmp(&key, &entry->key, sizeof(key));
         if (cmp < 0) {
             node = node->rb_left;
         } else if (cmp > 0) {
             node = node->rb_right;
         } else {
             entry->refcount--;
             if (entry->refcount == 0)
                 rb_erase(&entry->node, &nf->refcount);
 
             return entry;
         }
     }
 
     return NULL;
 }
 
 /**
  * ssam_nf_refcount_dec_free() - Decrement reference-/activation-count of the
  * given event and free its entry if the reference count reaches zero.
  * @nf:  The notifier system reference.
  * @reg: The registry used to enable/disable the event.
  * @id:  The event ID.
  *
  * Decrements the reference-/activation-count of the specified event, freeing
  * its entry if it reaches zero.
  *
  * Note: ``nf->lock`` must be held when calling this function.
  */
 static void ssam_nf_refcount_dec_free(struct ssam_nf *nf,
                       struct ssam_event_registry reg,
                       struct ssam_event_id id)
 {
     struct ssam_nf_refcount_entry *entry;
 
     lockdep_assert_held(&nf->lock);
 
     entry = ssam_nf_refcount_dec(nf, reg, id);
     if (entry && entry->refcount == 0)
         kfree(entry);
 }
 
 /**
  * ssam_nf_refcount_empty() - Test if the notification system has any
  * enabled/active events.
  * @nf: The notification system.
  */
 static bool ssam_nf_refcount_empty(struct ssam_nf *nf)
 {
     return RB_EMPTY_ROOT(&nf->refcount);
 }
 
 /**
  * ssam_nf_call() - Call notification callbacks for the provided event.
  * @nf:    The notifier system
  * @dev:   The associated device, only used for logging.
  * @rqid:  The request ID of the event.
  * @event: The event provided to the callbacks.
  *
  * Execute registered callbacks in order of their priority until either no
  * callback is left or a callback returns a value with the %SSAM_NOTIF_STOP
  * bit set. Note that this bit is set automatically when converting non-zero
  * error values via ssam_notifier_from_errno() to notifier values.
  *
  * Also note that any callback that could handle an event should return a value
  * with bit %SSAM_NOTIF_HANDLED set, indicating that the event does not go
  * unhandled/ignored. In case no registered callback could handle an event,
  * this function will emit a warning.
  *
  * In case a callback failed, this function will emit an error message.
  */
 static void ssam_nf_call(struct ssam_nf *nf, struct device *dev, u16 rqid,
              struct ssam_event *event)
 {
     struct ssam_nf_head *nf_head;
     int status, nf_ret;
 
     if (!ssh_rqid_is_event(rqid)) {
         dev_warn(dev, "event: unsupported rqid: %#06x\n", rqid);
         return;
     }
 
     nf_head = &nf->head[ssh_rqid_to_event(rqid)];
     nf_ret = ssam_nfblk_call_chain(nf_head, event);
     status = ssam_notifier_to_errno(nf_ret);
 
     if (status < 0) {
         dev_err(dev,
             "event: error handling event: %d (tc: %#04x, tid: %#04x, cid: %#04x, iid: %#04x)\n",
             status, event->target_category, event->target_id,
             event->command_id, event->instance_id);
     } else if (!(nf_ret & SSAM_NOTIF_HANDLED)) {
         dev_warn(dev,
              "event: unhandled event (rqid: %#04x, tc: %#04x, tid: %#04x, cid: %#04x, iid: %#04x)\n",
              rqid, event->target_category, event->target_id,
              event->command_id, event->instance_id);
     }
 }
 
 /**
  * ssam_nf_init() - Initialize the notifier system.
  * @nf: The notifier system to initialize.
  */
 static int ssam_nf_init(struct ssam_nf *nf)
 {
     int i, status;
 
     for (i = 0; i < SSH_NUM_EVENTS; i++) {
         status = ssam_nf_head_init(&nf->head[i]);
         if (status)
             break;
     }
 
     if (status) {
         while (i--)
             ssam_nf_head_destroy(&nf->head[i]);
 
         return status;
     }
 
     mutex_init(&nf->lock);
     return 0;
 }
 
 /**
  * ssam_nf_destroy() - Deinitialize the notifier system.
  * @nf: The notifier system to deinitialize.
  */
 static void ssam_nf_destroy(struct ssam_nf *nf)
 {
     int i;
 
     for (i = 0; i < SSH_NUM_EVENTS; i++)
         ssam_nf_head_destroy(&nf->head[i]);
 
     mutex_destroy(&nf->lock);
 }
 
 
 /* -- Event/async request completion system. -------------------------------- */
 
 #define SSAM_CPLT_WQ_NAME   "ssam_cpltq"
 
 /*
  * SSAM_CPLT_WQ_BATCH - Maximum number of event item completions executed per
  * work execution. Used to prevent livelocking of the workqueue. Value chosen
  * via educated guess, may be adjusted.
  */
 #define SSAM_CPLT_WQ_BATCH  10
 
 /*
  * SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN - Maximum payload length for a cached
  * &struct ssam_event_item.
  *
  * This length has been chosen to be accommodate standard touchpad and
  * keyboard input events. Events with larger payloads will be allocated
  * separately.
  */
 #define SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN   32
 
 static struct kmem_cache *ssam_event_item_cache;
 
 /**
  * ssam_event_item_cache_init() - Initialize the event item cache.
  */
 int ssam_event_item_cache_init(void)
 {
     const unsigned int size = sizeof(struct ssam_event_item)
                   + SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN;
     const unsigned int align = __alignof__(struct ssam_event_item);
     struct kmem_cache *cache;
 
     cache = kmem_cache_create("ssam_event_item", size, align, 0, NULL);
     if (!cache)
         return -ENOMEM;
 
     ssam_event_item_cache = cache;
     return 0;
 }
 
 /**
  * ssam_event_item_cache_destroy() - Deinitialize the event item cache.
  */
 void ssam_event_item_cache_destroy(void)
 {
     kmem_cache_destroy(ssam_event_item_cache);
     ssam_event_item_cache = NULL;
 }
 
 static void __ssam_event_item_free_cached(struct ssam_event_item *item)
 {
     kmem_cache_free(ssam_event_item_cache, item);
 }
 
 static void __ssam_event_item_free_generic(struct ssam_event_item *item)
 {
     kfree(item);
 }
 
 /**
  * ssam_event_item_free() - Free the provided event item.
  * @item: The event item to free.
  */
 static void ssam_event_item_free(struct ssam_event_item *item)
 {
     trace_ssam_event_item_free(item);
     item->ops.free(item);
 }
 
 /**
  * ssam_event_item_alloc() - Allocate an event item with the given payload size.
  * @len:   The event payload length.
  * @flags: The flags used for allocation.
  *
  * Allocate an event item with the given payload size, preferring allocation
  * from the event item cache if the payload is small enough (i.e. smaller than
  * %SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN). Sets the item operations and payload
  * length values. The item free callback (``ops.free``) should not be
  * overwritten after this call.
  *
  * Return: Returns the newly allocated event item.
  */
 static struct ssam_event_item *ssam_event_item_alloc(size_t len, gfp_t flags)
 {
     struct ssam_event_item *item;
 
     if (len <= SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN) {
         item = kmem_cache_alloc(ssam_event_item_cache, flags);
         if (!item)
             return NULL;
 
         item->ops.free = __ssam_event_item_free_cached;
     } else {
         item = kzalloc(struct_size(item, event.data, len), flags);
         if (!item)
             return NULL;
 
         item->ops.free = __ssam_event_item_free_generic;
     }
 
     item->event.length = len;
 
     trace_ssam_event_item_alloc(item, len);
     return item;
 }
 
 /**
  * ssam_event_queue_push() - Push an event item to the event queue.
  * @q:    The event queue.
  * @item: The item to add.
  */
 static void ssam_event_queue_push(struct ssam_event_queue *q,
                   struct ssam_event_item *item)
 {
     spin_lock(&q->lock);
     list_add_tail(&item->node, &q->head);
     spin_unlock(&q->lock);
 }
 
 /**
  * ssam_event_queue_pop() - Pop the next event item from the event queue.
  * @q: The event queue.
  *
  * Returns and removes the next event item from the queue. Returns %NULL If
  * there is no event item left.
  */
 static struct ssam_event_item *ssam_event_queue_pop(struct ssam_event_queue *q)
 {
     struct ssam_event_item *item;
 
     spin_lock(&q->lock);
     item = list_first_entry_or_null(&q->head, struct ssam_event_item, node);
     if (item)
         list_del(&item->node);
     spin_unlock(&q->lock);
 
     return item;
 }
 
 /**
  * ssam_event_queue_is_empty() - Check if the event queue is empty.
  * @q: The event queue.
  */
 static bool ssam_event_queue_is_empty(struct ssam_event_queue *q)
 {
     bool empty;
 
     spin_lock(&q->lock);
     empty = list_empty(&q->head);
     spin_unlock(&q->lock);
 
     return empty;
 }
 
 /**
  * ssam_cplt_get_event_queue() - Get the event queue for the given parameters.
  * @cplt: The completion system on which to look for the queue.
  * @tid:  The target ID of the queue.
  * @rqid: The request ID representing the event ID for which to get the queue.
  *
  * Return: Returns the event queue corresponding to the event type described
  * by the given parameters. If the request ID does not represent an event,
  * this function returns %NULL. If the target ID is not supported, this
  * function will fall back to the default target ID (``tid = 1``).
  */
 static
 struct ssam_event_queue *ssam_cplt_get_event_queue(struct ssam_cplt *cplt,
                            u8 tid, u16 rqid)
 {
     u16 event = ssh_rqid_to_event(rqid);
     u16 tidx = ssh_tid_to_index(tid);
 
     if (!ssh_rqid_is_event(rqid)) {
         dev_err(cplt->dev, "event: unsupported request ID: %#06x\n", rqid);
         return NULL;
     }
 
     if (!ssh_tid_is_valid(tid)) {
         dev_warn(cplt->dev, "event: unsupported target ID: %u\n", tid);
         tidx = 0;
     }
 
     return &cplt->event.target[tidx].queue[event];
 }
 
 /**
  * ssam_cplt_submit() - Submit a work item to the completion system workqueue.
  * @cplt: The completion system.
  * @work: The work item to submit.
  */
 static bool ssam_cplt_submit(struct ssam_cplt *cplt, struct work_struct *work)
 {
     return queue_work(cplt->wq, work);
 }
 
 /**
  * ssam_cplt_submit_event() - Submit an event to the completion system.
  * @cplt: The completion system.
  * @item: The event item to submit.
  *
  * Submits the event to the completion system by queuing it on the event item
  * queue and queuing the respective event queue work item on the completion
  * workqueue, which will eventually complete the event.
  *
  * Return: Returns zero on success, %-EINVAL if there is no event queue that
  * can handle the given event item.
  */
 static int ssam_cplt_submit_event(struct ssam_cplt *cplt,
                   struct ssam_event_item *item)
 {
     struct ssam_event_queue *evq;
 
     evq = ssam_cplt_get_event_queue(cplt, item->event.target_id, item->rqid);
     if (!evq)
         return -EINVAL;
 
     ssam_event_queue_push(evq, item);
     ssam_cplt_submit(cplt, &evq->work);
     return 0;
 }
 
 /**
  * ssam_cplt_flush() - Flush the completion system.
  * @cplt: The completion system.
  *
  * Flush the completion system by waiting until all currently submitted work
  * items have been completed.
  *
  * Note: This function does not guarantee that all events will have been
  * handled once this call terminates. In case of a larger number of
  * to-be-completed events, the event queue work function may re-schedule its
  * work item, which this flush operation will ignore.
  *
  * This operation is only intended to, during normal operation prior to
  * shutdown, try to complete most events and requests to get them out of the
  * system while the system is still fully operational. It does not aim to
  * provide any guarantee that all of them have been handled.
  */
 static void ssam_cplt_flush(struct ssam_cplt *cplt)
 {
     flush_workqueue(cplt->wq);
 }
 
 static void ssam_event_queue_work_fn(struct work_struct *work)
 {
     struct ssam_event_queue *queue;
     struct ssam_event_item *item;
     struct ssam_nf *nf;
     struct device *dev;
     unsigned int iterations = SSAM_CPLT_WQ_BATCH;
 
     queue = container_of(work, struct ssam_event_queue, work);
     nf = &queue->cplt->event.notif;
     dev = queue->cplt->dev;
 
     /* Limit number of processed events to avoid livelocking. */
     do {
         item = ssam_event_queue_pop(queue);
         if (!item)
             return;
 
         ssam_nf_call(nf, dev, item->rqid, &item->event);
         ssam_event_item_free(item);
     } while (--iterations);
 
     if (!ssam_event_queue_is_empty(queue))
         ssam_cplt_submit(queue->cplt, &queue->work);
 }
 
 /**
  * ssam_event_queue_init() - Initialize an event queue.
  * @cplt: The completion system on which the queue resides.
  * @evq:  The event queue to initialize.
  */
 static void ssam_event_queue_init(struct ssam_cplt *cplt,
                   struct ssam_event_queue *evq)
 {
     evq->cplt = cplt;
     spin_lock_init(&evq->lock);
     INIT_LIST_HEAD(&evq->head);
     INIT_WORK(&evq->work, ssam_event_queue_work_fn);
 }
 
 /**
  * ssam_cplt_init() - Initialize completion system.
  * @cplt: The completion system to initialize.
  * @dev:  The device used for logging.
  */
 static int ssam_cplt_init(struct ssam_cplt *cplt, struct device *dev)
 {
     struct ssam_event_target *target;
     int status, c, i;
 
     cplt->dev = dev;
 
     cplt->wq = create_workqueue(SSAM_CPLT_WQ_NAME);
     if (!cplt->wq)
         return -ENOMEM;
 
     for (c = 0; c < ARRAY_SIZE(cplt->event.target); c++) {
         target = &cplt->event.target[c];
 
         for (i = 0; i < ARRAY_SIZE(target->queue); i++)
             ssam_event_queue_init(cplt, &target->queue[i]);
     }
 
     status = ssam_nf_init(&cplt->event.notif);
     if (status)
         destroy_workqueue(cplt->wq);
 
     return status;
 }
 
 /**
  * ssam_cplt_destroy() - Deinitialize the completion system.
  * @cplt: The completion system to deinitialize.
  *
  * Deinitialize the given completion system and ensure that all pending, i.e.
  * yet-to-be-completed, event items and requests have been handled.
  */
 static void ssam_cplt_destroy(struct ssam_cplt *cplt)
 {
     /*
      * Note: destroy_workqueue ensures that all currently queued work will
      * be fully completed and the workqueue drained. This means that this
      * call will inherently also free any queued ssam_event_items, thus we
      * don't have to take care of that here explicitly.
      */
     destroy_workqueue(cplt->wq);
     ssam_nf_destroy(&cplt->event.notif);
 }
 
 
 /* -- Main SSAM device structures. ------------------------------------------ */
 
 /**
  * ssam_controller_device() - Get the &struct device associated with this
  * controller.
  * @c: The controller for which to get the device.
  *
  * Return: Returns the &struct device associated with this controller,
  * providing its lower-level transport.
  */
 struct device *ssam_controller_device(struct ssam_controller *c)
 {
     return ssh_rtl_get_device(&c->rtl);
 }
 EXPORT_SYMBOL_GPL(ssam_controller_device);
 
 static void __ssam_controller_release(struct kref *kref)
 {
     struct ssam_controller *ctrl = to_ssam_controller(kref, kref);
 
     /*
      * The lock-call here is to satisfy lockdep. At this point we really
      * expect this to be the last remaining reference to the controller.
      * Anything else is a bug.
      */
     ssam_controller_lock(ctrl);
     ssam_controller_destroy(ctrl);
     ssam_controller_unlock(ctrl);
 
     kfree(ctrl);
 }
 
 /**
  * ssam_controller_get() - Increment reference count of controller.
  * @c: The controller.
  *
  * Return: Returns the controller provided as input.
  */
 struct ssam_controller *ssam_controller_get(struct ssam_controller *c)
 {
     if (c)
         kref_get(&c->kref);
     return c;
 }
 EXPORT_SYMBOL_GPL(ssam_controller_get);
 
 /**
  * ssam_controller_put() - Decrement reference count of controller.
  * @c: The controller.
  */
 void ssam_controller_put(struct ssam_controller *c)
 {
     if (c)
         kref_put(&c->kref, __ssam_controller_release);
 }
 EXPORT_SYMBOL_GPL(ssam_controller_put);
 
 /**
  * ssam_controller_statelock() - Lock the controller against state transitions.
  * @c: The controller to lock.
  *
  * Lock the controller against state transitions. Holding this lock guarantees
  * that the controller will not transition between states, i.e. if the
  * controller is in state "started", when this lock has been acquired, it will
  * remain in this state at least until the lock has been released.
  *
  * Multiple clients may concurrently hold this lock. In other words: The
  * ``statelock`` functions represent the read-lock part of a r/w-semaphore.
  * Actions causing state transitions of the controller must be executed while
  * holding the write-part of this r/w-semaphore (see ssam_controller_lock()
  * and ssam_controller_unlock() for that).
  *
  * See ssam_controller_stateunlock() for the corresponding unlock function.
  */
 void ssam_controller_statelock(struct ssam_controller *c)
 {
     down_read(&c->lock);
 }
 EXPORT_SYMBOL_GPL(ssam_controller_statelock);
 
 /**
  * ssam_controller_stateunlock() - Unlock controller state transitions.
  * @c: The controller to unlock.
  *
  * See ssam_controller_statelock() for the corresponding lock function.
  */
 void ssam_controller_stateunlock(struct ssam_controller *c)
 {
     up_read(&c->lock);
 }
 EXPORT_SYMBOL_GPL(ssam_controller_stateunlock);
 
 /**
  * ssam_controller_lock() - Acquire the main controller lock.
  * @c: The controller to lock.
  *
  * This lock must be held for any state transitions, including transition to
  * suspend/resumed states and during shutdown. See ssam_controller_statelock()
  * for more details on controller locking.
  *
  * See ssam_controller_unlock() for the corresponding unlock function.
  */
 void ssam_controller_lock(struct ssam_controller *c)
 {
     down_write(&c->lock);
 }
 
 /*
  * ssam_controller_unlock() - Release the main controller lock.
  * @c: The controller to unlock.
  *
  * See ssam_controller_lock() for the corresponding lock function.
  */
 void ssam_controller_unlock(struct ssam_controller *c)
 {
     up_write(&c->lock);
 }
 
 static void ssam_handle_event(struct ssh_rtl *rtl,
                   const struct ssh_command *cmd,
                   const struct ssam_span *data)
 {
     struct ssam_controller *ctrl = to_ssam_controller(rtl, rtl);
     struct ssam_event_item *item;
 
     item = ssam_event_item_alloc(data->len, GFP_KERNEL);
     if (!item)
         return;
 
     item->rqid = get_unaligned_le16(&cmd->rqid);
     item->event.target_category = cmd->tc;
     item->event.target_id = cmd->tid_in;
     item->event.command_id = cmd->cid;
     item->event.instance_id = cmd->iid;
     memcpy(&item->event.data[0], data->ptr, data->len);
 
     if (WARN_ON(ssam_cplt_submit_event(&ctrl->cplt, item)))
         ssam_event_item_free(item);
 }
 
 static const struct ssh_rtl_ops ssam_rtl_ops = {
     .handle_event = ssam_handle_event,
 };
 
 static bool ssam_notifier_is_empty(struct ssam_controller *ctrl);
 static void ssam_notifier_unregister_all(struct ssam_controller *ctrl);
 
 #define SSAM_SSH_DSM_REVISION   0
 
 /* d5e383e1-d892-4a76-89fc-f6aaae7ed5b5 */
 static const guid_t SSAM_SSH_DSM_GUID =
     GUID_INIT(0xd5e383e1, 0xd892, 0x4a76,
           0x89, 0xfc, 0xf6, 0xaa, 0xae, 0x7e, 0xd5, 0xb5);
 
 enum ssh_dsm_fn {
     SSH_DSM_FN_SSH_POWER_PROFILE             = 0x05,
     SSH_DSM_FN_SCREEN_ON_SLEEP_IDLE_TIMEOUT  = 0x06,
     SSH_DSM_FN_SCREEN_OFF_SLEEP_IDLE_TIMEOUT = 0x07,
     SSH_DSM_FN_D3_CLOSES_HANDLE              = 0x08,
     SSH_DSM_FN_SSH_BUFFER_SIZE               = 0x09,
 };
 
 static int ssam_dsm_get_functions(acpi_handle handle, u64 *funcs)
 {
     union acpi_object *obj;
     u64 mask = 0;
     int i;
 
     *funcs = 0;
 
     /*
      * The _DSM function is only present on newer models. It is not
      * present on 5th and 6th generation devices (i.e. up to and including
      * Surface Pro 6, Surface Laptop 2, Surface Book 2).
      *
      * If the _DSM is not present, indicate that no function is supported.
      * This will result in default values being set.
      */
     if (!acpi_has_method(handle, "_DSM"))
         return 0;
 
     obj = acpi_evaluate_dsm_typed(handle, &SSAM_SSH_DSM_GUID,
                       SSAM_SSH_DSM_REVISION, 0, NULL,
                       ACPI_TYPE_BUFFER);
     if (!obj)
         return -EIO;
 
     for (i = 0; i < obj->buffer.length && i < 8; i++)
         mask |= (((u64)obj->buffer.pointer[i]) << (i * 8));
 
     if (mask & BIT(0))
         *funcs = mask;
 
     ACPI_FREE(obj);
     return 0;
 }
 
 static int ssam_dsm_load_u32(acpi_handle handle, u64 funcs, u64 func, u32 *ret)
 {
     union acpi_object *obj;
     u64 val;
 
     if (!(funcs & BIT_ULL(func)))
         return 0; /* Not supported, leave *ret at its default value */
 
     obj = acpi_evaluate_dsm_typed(handle, &SSAM_SSH_DSM_GUID,
                       SSAM_SSH_DSM_REVISION, func, NULL,
                       ACPI_TYPE_INTEGER);
     if (!obj)
         return -EIO;
 
     val = obj->integer.value;
     ACPI_FREE(obj);
 
     if (val > U32_MAX)
         return -ERANGE;
 
     *ret = val;
     return 0;
 }
 
 /**
  * ssam_controller_caps_load_from_acpi() - Load controller capabilities from
  * ACPI _DSM.
  * @handle: The handle of the ACPI controller/SSH device.
  * @caps:   Where to store the capabilities in.
  *
  * Initializes the given controller capabilities with default values, then
  * checks and, if the respective _DSM functions are available, loads the
  * actual capabilities from the _DSM.
  *
  * Return: Returns zero on success, a negative error code on failure.
  */
 static
 int ssam_controller_caps_load_from_acpi(acpi_handle handle,
                     struct ssam_controller_caps *caps)
 {
     u32 d3_closes_handle = false;
     u64 funcs;
     int status;
 
     /* Set defaults. */
     caps->ssh_power_profile = U32_MAX;
     caps->screen_on_sleep_idle_timeout = U32_MAX;
     caps->screen_off_sleep_idle_timeout = U32_MAX;
     caps->d3_closes_handle = false;
     caps->ssh_buffer_size = U32_MAX;
 
     /* Pre-load supported DSM functions. */
     status = ssam_dsm_get_functions(handle, &funcs);
     if (status)
         return status;
 
     /* Load actual values from ACPI, if present. */
     status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_SSH_POWER_PROFILE,
                    &caps->ssh_power_profile);
     if (status)
         return status;
 
     status = ssam_dsm_load_u32(handle, funcs,
                    SSH_DSM_FN_SCREEN_ON_SLEEP_IDLE_TIMEOUT,
                    &caps->screen_on_sleep_idle_timeout);
     if (status)
         return status;
 
     status = ssam_dsm_load_u32(handle, funcs,
                    SSH_DSM_FN_SCREEN_OFF_SLEEP_IDLE_TIMEOUT,
                    &caps->screen_off_sleep_idle_timeout);
     if (status)
         return status;
 
     status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_D3_CLOSES_HANDLE,
                    &d3_closes_handle);
     if (status)
         return status;
 
     caps->d3_closes_handle = !!d3_closes_handle;
 
     status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_SSH_BUFFER_SIZE,
                    &caps->ssh_buffer_size);
     if (status)
         return status;
 
     return 0;
 }
 
 /**
  * ssam_controller_init() - Initialize SSAM controller.
  * @ctrl:   The controller to initialize.
  * @serdev: The serial device representing the underlying data transport.
  *
  * Initializes the given controller. Does neither start receiver nor
  * transmitter threads. After this call, the controller has to be hooked up to
  * the serdev core separately via &struct serdev_device_ops, relaying calls to
  * ssam_controller_receive_buf() and ssam_controller_write_wakeup(). Once the
  * controller has been hooked up, transmitter and receiver threads may be
  * started via ssam_controller_start(). These setup steps need to be completed
  * before controller can be used for requests.
  */
 int ssam_controller_init(struct ssam_controller *ctrl,
              struct serdev_device *serdev)
 {
     acpi_handle handle = ACPI_HANDLE(&serdev->dev);
     int status;
 
     init_rwsem(&ctrl->lock);
     kref_init(&ctrl->kref);
 
     status = ssam_controller_caps_load_from_acpi(handle, &ctrl->caps);
     if (status)
         return status;
 
     dev_dbg(&serdev->dev,
         "device capabilities:\n"
         "  ssh_power_profile:             %u\n"
         "  ssh_buffer_size:               %u\n"
         "  screen_on_sleep_idle_timeout:  %u\n"
         "  screen_off_sleep_idle_timeout: %u\n"
         "  d3_closes_handle:              %u\n",
         ctrl->caps.ssh_power_profile,
         ctrl->caps.ssh_buffer_size,
         ctrl->caps.screen_on_sleep_idle_timeout,
         ctrl->caps.screen_off_sleep_idle_timeout,
         ctrl->caps.d3_closes_handle);
 
     ssh_seq_reset(&ctrl->counter.seq);
     ssh_rqid_reset(&ctrl->counter.rqid);
 
     /* Initialize event/request completion system. */
     status = ssam_cplt_init(&ctrl->cplt, &serdev->dev);
     if (status)
         return status;
 
     /* Initialize request and packet transport layers. */
     status = ssh_rtl_init(&ctrl->rtl, serdev, &ssam_rtl_ops);
     if (status) {
         ssam_cplt_destroy(&ctrl->cplt);
         return status;
     }
 
     /*
      * Set state via write_once even though we expect to be in an
      * exclusive context, due to smoke-testing in
      * ssam_request_sync_submit().
      */
     WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_INITIALIZED);
     return 0;
 }
 
 /**
  * ssam_controller_start() - Start the receiver and transmitter threads of the
  * controller.
  * @ctrl: The controller.
  *
  * Note: When this function is called, the controller should be properly
  * hooked up to the serdev core via &struct serdev_device_ops. Please refer
  * to ssam_controller_init() for more details on controller initialization.
  *
  * This function must be called with the main controller lock held (i.e. by
  * calling ssam_controller_lock()).
  */
 int ssam_controller_start(struct ssam_controller *ctrl)
 {
     int status;
 
     lockdep_assert_held_write(&ctrl->lock);
 
     if (ctrl->state != SSAM_CONTROLLER_INITIALIZED)
         return -EINVAL;
 
     status = ssh_rtl_start(&ctrl->rtl);
     if (status)
         return status;
 
     /*
      * Set state via write_once even though we expect to be locked/in an
      * exclusive context, due to smoke-testing in
      * ssam_request_sync_submit().
      */
     WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STARTED);
     return 0;
 }
 
 /*
  * SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT - Timeout for flushing requests during
  * shutdown.
  *
  * Chosen to be larger than one full request timeout, including packets timing
  * out. This value should give ample time to complete any outstanding requests
  * during normal operation and account for the odd package timeout.
  */
 #define SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT    msecs_to_jiffies(5000)
 
 /**
  * ssam_controller_shutdown() - Shut down the controller.
  * @ctrl: The controller.
  *
  * Shuts down the controller by flushing all pending requests and stopping the
  * transmitter and receiver threads. All requests submitted after this call
  * will fail with %-ESHUTDOWN. While it is discouraged to do so, this function
  * is safe to use in parallel with ongoing request submission.
  *
  * In the course of this shutdown procedure, all currently registered
  * notifiers will be unregistered. It is, however, strongly recommended to not
  * rely on this behavior, and instead the party registering the notifier
  * should unregister it before the controller gets shut down, e.g. via the
  * SSAM bus which guarantees client devices to be removed before a shutdown.
  *
  * Note that events may still be pending after this call, but, due to the
  * notifiers being unregistered, these events will be dropped when the
  * controller is subsequently destroyed via ssam_controller_destroy().
  *
  * This function must be called with the main controller lock held (i.e. by
  * calling ssam_controller_lock()).
  */
 void ssam_controller_shutdown(struct ssam_controller *ctrl)
 {
     enum ssam_controller_state s = ctrl->state;
     int status;
 
     lockdep_assert_held_write(&ctrl->lock);
 
     if (s == SSAM_CONTROLLER_UNINITIALIZED || s == SSAM_CONTROLLER_STOPPED)
         return;
 
     /*
      * Try to flush pending events and requests while everything still
      * works. Note: There may still be packets and/or requests in the
      * system after this call (e.g. via control packets submitted by the
      * packet transport layer or flush timeout / failure, ...). Those will
      * be handled with the ssh_rtl_shutdown() call below.
      */
     status = ssh_rtl_flush(&ctrl->rtl, SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT);
     if (status) {
         ssam_err(ctrl, "failed to flush request transport layer: %d\n",
              status);
     }
 
     /* Try to flush all currently completing requests and events. */
     ssam_cplt_flush(&ctrl->cplt);
 
     /*
      * We expect all notifiers to have been removed by the respective client
      * driver that set them up at this point. If this warning occurs, some
      * client driver has not done that...
      */
     WARN_ON(!ssam_notifier_is_empty(ctrl));
 
     /*
      * Nevertheless, we should still take care of drivers that don't behave
      * well. Thus disable all enabled events, unregister all notifiers.
      */
     ssam_notifier_unregister_all(ctrl);
 
     /*
      * Cancel remaining requests. Ensure no new ones can be queued and stop
      * threads.
      */
     ssh_rtl_shutdown(&ctrl->rtl);
 
     /*
      * Set state via write_once even though we expect to be locked/in an
      * exclusive context, due to smoke-testing in
      * ssam_request_sync_submit().
      */
     WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STOPPED);
     ctrl->rtl.ptl.serdev = NULL;
 }
 
 /**
  * ssam_controller_destroy() - Destroy the controller and free its resources.
  * @ctrl: The controller.
  *
  * Ensures that all resources associated with the controller get freed. This
  * function should only be called after the controller has been stopped via
  * ssam_controller_shutdown(). In general, this function should not be called
  * directly. The only valid place to call this function directly is during
  * initialization, before the controller has been fully initialized and passed
  * to other processes. This function is called automatically when the
  * reference count of the controller reaches zero.
  *
  * This function must be called with the main controller lock held (i.e. by
  * calling ssam_controller_lock()).
  */
 void ssam_controller_destroy(struct ssam_controller *ctrl)
 {
     lockdep_assert_held_write(&ctrl->lock);
 
     if (ctrl->state == SSAM_CONTROLLER_UNINITIALIZED)
         return;
 
     WARN_ON(ctrl->state != SSAM_CONTROLLER_STOPPED);
 
     /*
      * Note: New events could still have been received after the previous
      * flush in ssam_controller_shutdown, before the request transport layer
      * has been shut down. At this point, after the shutdown, we can be sure
      * that no new events will be queued. The call to ssam_cplt_destroy will
      * ensure that those remaining are being completed and freed.
      */
 
     /* Actually free resources. */
     ssam_cplt_destroy(&ctrl->cplt);
     ssh_rtl_destroy(&ctrl->rtl);
 
     /*
      * Set state via write_once even though we expect to be locked/in an
      * exclusive context, due to smoke-testing in
      * ssam_request_sync_submit().
      */
     WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_UNINITIALIZED);
 }
 
 /**
  * ssam_controller_suspend() - Suspend the controller.
  * @ctrl: The controller to suspend.
  *
  * Marks the controller as suspended. Note that display-off and D0-exit
  * notifications have to be sent manually before transitioning the controller
  * into the suspended state via this function.
  *
  * See ssam_controller_resume() for the corresponding resume function.
  *
  * Return: Returns %-EINVAL if the controller is currently not in the
  * "started" state.
  */
 int ssam_controller_suspend(struct ssam_controller *ctrl)
 {
     ssam_controller_lock(ctrl);
 
     if (ctrl->state != SSAM_CONTROLLER_STARTED) {
         ssam_controller_unlock(ctrl);
         return -EINVAL;
     }
 
     ssam_dbg(ctrl, "pm: suspending controller\n");
 
     /*
      * Set state via write_once even though we're locked, due to
      * smoke-testing in ssam_request_sync_submit().
      */
     WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_SUSPENDED);
 
     ssam_controller_unlock(ctrl);
     return 0;
 }
 
 /**
  * ssam_controller_resume() - Resume the controller from suspend.
  * @ctrl: The controller to resume.
  *
  * Resume the controller from the suspended state it was put into via
  * ssam_controller_suspend(). This function does not issue display-on and
  * D0-entry notifications. If required, those have to be sent manually after
  * this call.
  *
  * Return: Returns %-EINVAL if the controller is currently not suspended.
  */
 int ssam_controller_resume(struct ssam_controller *ctrl)
 {
     ssam_controller_lock(ctrl);
 
     if (ctrl->state != SSAM_CONTROLLER_SUSPENDED) {
         ssam_controller_unlock(ctrl);
         return -EINVAL;
     }
 
     ssam_dbg(ctrl, "pm: resuming controller\n");
 
     /*
      * Set state via write_once even though we're locked, due to
      * smoke-testing in ssam_request_sync_submit().
      */
     WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STARTED);
 
     ssam_controller_unlock(ctrl);
     return 0;
 }
 
 
 /* -- Top-level request interface ------------------------------------------- */
 
 /**
  * ssam_request_write_data() - Construct and write SAM request message to
  * buffer.
  * @buf:  The buffer to write the data to.
  * @ctrl: The controller via which the request will be sent.
  * @spec: The request data and specification.
  *
  * Constructs a SAM/SSH request message and writes it to the provided buffer.
  * The request and transport counters, specifically RQID and SEQ, will be set
  * in this call. These counters are obtained from the controller. It is thus
  * only valid to send the resulting message via the controller specified here.
  *
  * For calculation of the required buffer size, refer to the
  * SSH_COMMAND_MESSAGE_LENGTH() macro.
  *
  * Return: Returns the number of bytes used in the buffer on success. Returns
  * %-EINVAL if the payload length provided in the request specification is too
  * large (larger than %SSH_COMMAND_MAX_PAYLOAD_SIZE) or if the provided buffer
  * is too small.
  */
 ssize_t ssam_request_write_data(struct ssam_span *buf,
                 struct ssam_controller *ctrl,
                 const struct ssam_request *spec)
 {
     struct msgbuf msgb;
     u16 rqid;
     u8 seq;
 
     if (spec->length > SSH_COMMAND_MAX_PAYLOAD_SIZE)
         return -EINVAL;
 
     if (SSH_COMMAND_MESSAGE_LENGTH(spec->length) > buf->len)
         return -EINVAL;
 
     msgb_init(&msgb, buf->ptr, buf->len);
     seq = ssh_seq_next(&ctrl->counter.seq);
     rqid = ssh_rqid_next(&ctrl->counter.rqid);
     msgb_push_cmd(&msgb, seq, rqid, spec);
 
     return msgb_bytes_used(&msgb);
 }
 EXPORT_SYMBOL_GPL(ssam_request_write_data);
 
 static void ssam_request_sync_complete(struct ssh_request *rqst,
                        const struct ssh_command *cmd,
                        const struct ssam_span *data, int status)
 {
     struct ssh_rtl *rtl = ssh_request_rtl(rqst);
     struct ssam_request_sync *r;
 
     r = container_of(rqst, struct ssam_request_sync, base);
     r->status = status;
 
     if (r->resp)
         r->resp->length = 0;
 
     if (status) {
         rtl_dbg_cond(rtl, "rsp: request failed: %d\n", status);
         return;
     }
 
     if (!data)  /* Handle requests without a response. */
         return;
 
     if (!r->resp || !r->resp->pointer) {
         if (data->len)
             rtl_warn(rtl, "rsp: no response buffer provided, dropping data\n");
         return;
     }
 
     if (data->len > r->resp->capacity) {
         rtl_err(rtl,
             "rsp: response buffer too small, capacity: %zu bytes, got: %zu bytes\n",
             r->resp->capacity, data->len);
         r->status = -ENOSPC;
         return;
     }
 
     r->resp->length = data->len;
     memcpy(r->resp->pointer, data->ptr, data->len);
 }
 
 static void ssam_request_sync_release(struct ssh_request *rqst)
 {
     complete_all(&container_of(rqst, struct ssam_request_sync, base)->comp);
 }
 
 static const struct ssh_request_ops ssam_request_sync_ops = {
     .release = ssam_request_sync_release,
     .complete = ssam_request_sync_complete,
 };
 
 /**
  * ssam_request_sync_alloc() - Allocate a synchronous request.
  * @payload_len: The length of the request payload.
  * @flags:       Flags used for allocation.
  * @rqst:        Where to store the pointer to the allocated request.
  * @buffer:      Where to store the buffer descriptor for the message buffer of
  *               the request.
  *
  * Allocates a synchronous request with corresponding message buffer. The
  * request still needs to be initialized ssam_request_sync_init() before
  * it can be submitted, and the message buffer data must still be set to the
  * returned buffer via ssam_request_sync_set_data() after it has been filled,
  * if need be with adjusted message length.
  *
  * After use, the request and its corresponding message buffer should be freed
  * via ssam_request_sync_free(). The buffer must not be freed separately.
  *
  * Return: Returns zero on success, %-ENOMEM if the request could not be
  * allocated.
  */
 int ssam_request_sync_alloc(size_t payload_len, gfp_t flags,
                 struct ssam_request_sync **rqst,
                 struct ssam_span *buffer)
 {
     size_t msglen = SSH_COMMAND_MESSAGE_LENGTH(payload_len);
 
     *rqst = kzalloc(sizeof(**rqst) + msglen, flags);
     if (!*rqst)
         return -ENOMEM;
 
     buffer->ptr = (u8 *)(*rqst + 1);
     buffer->len = msglen;
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(ssam_request_sync_alloc);
 
 /**
  * ssam_request_sync_free() - Free a synchronous request.
  * @rqst: The request to be freed.
  *
  * Free a synchronous request and its corresponding buffer allocated with
  * ssam_request_sync_alloc(). Do not use for requests allocated on the stack
  * or via any other function.
  *
  * Warning: The caller must ensure that the request is not in use any more.
  * I.e. the caller must ensure that it has the only reference to the request
  * and the request is not currently pending. This means that the caller has
  * either never submitted the request, request submission has failed, or the
  * caller has waited until the submitted request has been completed via
  * ssam_request_sync_wait().
  */
 void ssam_request_sync_free(struct ssam_request_sync *rqst)
 {
     kfree(rqst);
 }
 EXPORT_SYMBOL_GPL(ssam_request_sync_free);
 
 /**
  * ssam_request_sync_init() - Initialize a synchronous request struct.
  * @rqst:  The request to initialize.
  * @flags: The request flags.
  *
  * Initializes the given request struct. Does not initialize the request
  * message data. This has to be done explicitly after this call via
  * ssam_request_sync_set_data() and the actual message data has to be written
  * via ssam_request_write_data().
  *
  * Return: Returns zero on success or %-EINVAL if the given flags are invalid.
  */
 int ssam_request_sync_init(struct ssam_request_sync *rqst,
                enum ssam_request_flags flags)
 {
     int status;
 
     status = ssh_request_init(&rqst->base, flags, &ssam_request_sync_ops);
     if (status)
         return status;
 
     init_completion(&rqst->comp);
     rqst->resp = NULL;
     rqst->status = 0;
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(ssam_request_sync_init);
 
 /**
  * ssam_request_sync_submit() - Submit a synchronous request.
  * @ctrl: The controller with which to submit the request.
  * @rqst: The request to submit.
  *
  * Submit a synchronous request. The request has to be initialized and
  * properly set up, including response buffer (may be %NULL if no response is
  * expected) and command message data. This function does not wait for the
  * request to be completed.
  *
  * If this function succeeds, ssam_request_sync_wait() must be used to ensure
  * that the request has been completed before the response data can be
  * accessed and/or the request can be freed. On failure, the request may
  * immediately be freed.
  *
  * This function may only be used if the controller is active, i.e. has been
  * initialized and not suspended.
  */
 int ssam_request_sync_submit(struct ssam_controller *ctrl,
                  struct ssam_request_sync *rqst)
 {
     int status;
 
     /*
      * This is only a superficial check. In general, the caller needs to
      * ensure that the controller is initialized and is not (and does not
      * get) suspended during use, i.e. until the request has been completed
      * (if _absolutely_ necessary, by use of ssam_controller_statelock/
      * ssam_controller_stateunlock, but something like ssam_client_link
      * should be preferred as this needs to last until the request has been
      * completed).
      *
      * Note that it is actually safe to use this function while the
      * controller is in the process of being shut down (as ssh_rtl_submit
      * is safe with regards to this), but it is generally discouraged to do
      * so.
      */
     if (WARN_ON(READ_ONCE(ctrl->state) != SSAM_CONTROLLER_STARTED)) {
         ssh_request_put(&rqst->base);
         return -ENODEV;
     }
 
     status = ssh_rtl_submit(&ctrl->rtl, &rqst->base);
     ssh_request_put(&rqst->base);
 
     return status;
 }
 EXPORT_SYMBOL_GPL(ssam_request_sync_submit);
 
 /**
  * ssam_request_sync() - Execute a synchronous request.
  * @ctrl: The controller via which the request will be submitted.
  * @spec: The request specification and payload.
  * @rsp:  The response buffer.
  *
  * Allocates a synchronous request with its message data buffer on the heap
  * via ssam_request_sync_alloc(), fully initializes it via the provided
  * request specification, submits it, and finally waits for its completion
  * before freeing it and returning its status.
  *
  * Return: Returns the status of the request or any failure during setup.
  */
 int ssam_request_sync(struct ssam_controller *ctrl,
               const struct ssam_request *spec,
               struct ssam_response *rsp)
 {
     struct ssam_request_sync *rqst;
     struct ssam_span buf;
     ssize_t len;
     int status;
 
     status = ssam_request_sync_alloc(spec->length, GFP_KERNEL, &rqst, &buf);
     if (status)
         return status;
 
     status = ssam_request_sync_init(rqst, spec->flags);
     if (status)
         return status;
 
     ssam_request_sync_set_resp(rqst, rsp);
 
     len = ssam_request_write_data(&buf, ctrl, spec);
     if (len < 0) {
         ssam_request_sync_free(rqst);
         return len;
     }
 
     ssam_request_sync_set_data(rqst, buf.ptr, len);
 
     status = ssam_request_sync_submit(ctrl, rqst);
     if (!status)
         status = ssam_request_sync_wait(rqst);
 
     ssam_request_sync_free(rqst);
     return status;
 }
 EXPORT_SYMBOL_GPL(ssam_request_sync);
 
 /**
  * ssam_request_sync_with_buffer() - Execute a synchronous request with the
  * provided buffer as back-end for the message buffer.
  * @ctrl: The controller via which the request will be submitted.
  * @spec: The request specification and payload.
  * @rsp:  The response buffer.
  * @buf:  The buffer for the request message data.
  *
  * Allocates a synchronous request struct on the stack, fully initializes it
  * using the provided buffer as message data buffer, submits it, and then
  * waits for its completion before returning its status. The
  * SSH_COMMAND_MESSAGE_LENGTH() macro can be used to compute the required
  * message buffer size.
  *
  * This function does essentially the same as ssam_request_sync(), but instead
  * of dynamically allocating the request and message data buffer, it uses the
  * provided message data buffer and stores the (small) request struct on the
  * heap.
  *
  * Return: Returns the status of the request or any failure during setup.
  */
 int ssam_request_sync_with_buffer(struct ssam_controller *ctrl,
                   const struct ssam_request *spec,
                   struct ssam_response *rsp,
                   struct ssam_span *buf)
 {
     struct ssam_request_sync rqst;
     ssize_t len;
     int status;
 
     status = ssam_request_sync_init(&rqst, spec->flags);
     if (status)
         return status;
 
     ssam_request_sync_set_resp(&rqst, rsp);
 
     len = ssam_request_write_data(buf, ctrl, spec);
     if (len < 0)
         return len;
 
     ssam_request_sync_set_data(&rqst, buf->ptr, len);
 
     status = ssam_request_sync_submit(ctrl, &rqst);
     if (!status)
         status = ssam_request_sync_wait(&rqst);
 
     return status;
 }
 EXPORT_SYMBOL_GPL(ssam_request_sync_with_buffer);
 
 
 /* -- Internal SAM requests. ------------------------------------------------ */
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_get_firmware_version, __le32, {
     .target_category = SSAM_SSH_TC_SAM,
     .target_id       = 0x01,
     .command_id      = 0x13,
     .instance_id     = 0x00,
 });
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_display_off, u8, {
     .target_category = SSAM_SSH_TC_SAM,
     .target_id       = 0x01,
     .command_id      = 0x15,
     .instance_id     = 0x00,
 });
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_display_on, u8, {
     .target_category = SSAM_SSH_TC_SAM,
     .target_id       = 0x01,
     .command_id      = 0x16,
     .instance_id     = 0x00,
 });
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_d0_exit, u8, {
     .target_category = SSAM_SSH_TC_SAM,
     .target_id       = 0x01,
     .command_id      = 0x33,
     .instance_id     = 0x00,
 });
 
 SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_d0_entry, u8, {
     .target_category = SSAM_SSH_TC_SAM,
     .target_id       = 0x01,
     .command_id      = 0x34,
     .instance_id     = 0x00,
 });
 
 /**
  * struct ssh_notification_params - Command payload to enable/disable SSH
  * notifications.
  * @target_category: The target category for which notifications should be
  *                   enabled/disabled.
  * @flags:           Flags determining how notifications are being sent.
  * @request_id:      The request ID that is used to send these notifications.
  * @instance_id:     The specific instance in the given target category for
  *                   which notifications should be enabled.
  */
 struct ssh_notification_params {
     u8 target_category;
     u8 flags;
     __le16 request_id;
     u8 instance_id;
 } __packed;
 
 static_assert(sizeof(struct ssh_notification_params) == 5);
 
 static int __ssam_ssh_event_request(struct ssam_controller *ctrl,
                     struct ssam_event_registry reg, u8 cid,
                     struct ssam_event_id id, u8 flags)
 {
     struct ssh_notification_params params;
     struct ssam_request rqst;
     struct ssam_response result;
     int status;
 
     u16 rqid = ssh_tc_to_rqid(id.target_category);
     u8 buf = 0;
 
     /* Only allow RQIDs that lie within the event spectrum. */
     if (!ssh_rqid_is_event(rqid))
         return -EINVAL;
 
     params.target_category = id.target_category;
     params.instance_id = id.instance;
     params.flags = flags;
     put_unaligned_le16(rqid, &params.request_id);
 
     rqst.target_category = reg.target_category;
     rqst.target_id = reg.target_id;
     rqst.command_id = cid;
     rqst.instance_id = 0x00;
     rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
     rqst.length = sizeof(params);
     rqst.payload = (u8 *)&params;
 
     result.capacity = sizeof(buf);
     result.length = 0;
     result.pointer = &buf;
 
     status = ssam_retry(ssam_request_sync_onstack, ctrl, &rqst, &result,
                 sizeof(params));
 
     return status < 0 ? status : buf;
 }
 
 /**
  * ssam_ssh_event_enable() - Enable SSH event.
  * @ctrl:  The controller for which to enable the event.
  * @reg:   The event registry describing what request to use for enabling and
  *         disabling the event.
  * @id:    The event identifier.
  * @flags: The event flags.
  *
  * Enables the specified event on the EC. This function does not manage
  * reference counting of enabled events and is basically only a wrapper for
  * the raw EC request. If the specified event is already enabled, the EC will
  * ignore this request.
  *
  * Return: Returns the status of the executed SAM request (zero on success and
  * negative on direct failure) or %-EPROTO if the request response indicates a
  * failure.
  */
 static int ssam_ssh_event_enable(struct ssam_controller *ctrl,
                  struct ssam_event_registry reg,
                  struct ssam_event_id id, u8 flags)
 {
     int status;
 
     status = __ssam_ssh_event_request(ctrl, reg, reg.cid_enable, id, flags);
 
     if (status < 0 && status != -EINVAL) {
         ssam_err(ctrl,
              "failed to enable event source (tc: %#04x, iid: %#04x, reg: %#04x)\n",
              id.target_category, id.instance, reg.target_category);
     }
 
     if (status > 0) {
         ssam_err(ctrl,
              "unexpected result while enabling event source: %#04x (tc: %#04x, iid: %#04x, reg: %#04x)\n",
              status, id.target_category, id.instance, reg.target_category);
         return -EPROTO;
     }
 
     return status;
 }
 
 /**
  * ssam_ssh_event_disable() - Disable SSH event.
  * @ctrl:  The controller for which to disable the event.
  * @reg:   The event registry describing what request to use for enabling and
  *         disabling the event (must be same as used when enabling the event).
  * @id:    The event identifier.
  * @flags: The event flags (likely ignored for disabling of events).
  *
  * Disables the specified event on the EC. This function does not manage
  * reference counting of enabled events and is basically only a wrapper for
  * the raw EC request. If the specified event is already disabled, the EC will
  * ignore this request.
  *
  * Return: Returns the status of the executed SAM request (zero on success and
  * negative on direct failure) or %-EPROTO if the request response indicates a
  * failure.
  */
 static int ssam_ssh_event_disable(struct ssam_controller *ctrl,
                   struct ssam_event_registry reg,
                   struct ssam_event_id id, u8 flags)
 {
     int status;
 
     status = __ssam_ssh_event_request(ctrl, reg, reg.cid_disable, id, flags);
 
     if (status < 0 && status != -EINVAL) {
         ssam_err(ctrl,
              "failed to disable event source (tc: %#04x, iid: %#04x, reg: %#04x)\n",
              id.target_category, id.instance, reg.target_category);
     }
 
     if (status > 0) {
         ssam_err(ctrl,
              "unexpected result while disabling event source: %#04x (tc: %#04x, iid: %#04x, reg: %#04x)\n",
              status, id.target_category, id.instance, reg.target_category);
         return -EPROTO;
     }
 
     return status;
 }
 
 
 /* -- Wrappers for internal SAM requests. ----------------------------------- */
 
 /**
  * ssam_get_firmware_version() - Get the SAM/EC firmware version.
  * @ctrl:    The controller.
  * @version: Where to store the version number.
  *
  * Return: Returns zero on success or the status of the executed SAM request
  * if that request failed.
  */
 int ssam_get_firmware_version(struct ssam_controller *ctrl, u32 *version)
 {
     __le32 __version;
     int status;
 
     status = ssam_retry(ssam_ssh_get_firmware_version, ctrl, &__version);
     if (status)
         return status;
 
     *version = le32_to_cpu(__version);
     return 0;
 }
 
 /**
  * ssam_ctrl_notif_display_off() - Notify EC that the display has been turned
  * off.
  * @ctrl: The controller.
  *
  * Notify the EC that the display has been turned off and the driver may enter
  * a lower-power state. This will prevent events from being sent directly.
  * Rather, the EC signals an event by pulling the wakeup GPIO high for as long
  * as there are pending events. The events then need to be manually released,
  * one by one, via the GPIO callback request. All pending events accumulated
  * during this state can also be released by issuing the display-on
  * notification, e.g. via ssam_ctrl_notif_display_on(), which will also reset
  * the GPIO.
  *
  * On some devices, specifically ones with an integrated keyboard, the keyboard
  * backlight will be turned off by this call.
  *
  * This function will only send the display-off notification command if
  * display notifications are supported by the EC. Currently all known devices
  * support these notifications.
  *
  * Use ssam_ctrl_notif_display_on() to reverse the effects of this function.
  *
  * Return: Returns zero on success or if no request has been executed, the
  * status of the executed SAM request if that request failed, or %-EPROTO if
  * an unexpected response has been received.
  */
 int ssam_ctrl_notif_display_off(struct ssam_controller *ctrl)
 {
     int status;
     u8 response;
 
     ssam_dbg(ctrl, "pm: notifying display off\n");
 
     status = ssam_retry(ssam_ssh_notif_display_off, ctrl, &response);
     if (status)
         return status;
 
     if (response != 0) {
         ssam_err(ctrl, "unexpected response from display-off notification: %#04x\n",
              response);
         return -EPROTO;
     }
 
     return 0;
 }
 
 /**
  * ssam_ctrl_notif_display_on() - Notify EC that the display has been turned on.
  * @ctrl: The controller.
  *
  * Notify the EC that the display has been turned back on and the driver has
  * exited its lower-power state. This notification is the counterpart to the
  * display-off notification sent via ssam_ctrl_notif_display_off() and will
  * reverse its effects, including resetting events to their default behavior.
  *
  * This function will only send the display-on notification command if display
  * notifications are supported by the EC. Currently all known devices support
  * these notifications.
  *
  * See ssam_ctrl_notif_display_off() for more details.
  *
  * Return: Returns zero on success or if no request has been executed, the
  * status of the executed SAM request if that request failed, or %-EPROTO if
  * an unexpected response has been received.
  */
 int ssam_ctrl_notif_display_on(struct ssam_controller *ctrl)
 {
     int status;
     u8 response;
 
     ssam_dbg(ctrl, "pm: notifying display on\n");
 
     status = ssam_retry(ssam_ssh_notif_display_on, ctrl, &response);
     if (status)
         return status;
 
     if (response != 0) {
         ssam_err(ctrl, "unexpected response from display-on notification: %#04x\n",
              response);
         return -EPROTO;
     }
 
     return 0;
 }
 
 /**
  * ssam_ctrl_notif_d0_exit() - Notify EC that the driver/device exits the D0
  * power state.
  * @ctrl: The controller
  *
  * Notifies the EC that the driver prepares to exit the D0 power state in
  * favor of a lower-power state. Exact effects of this function related to the
  * EC are currently unknown.
  *
  * This function will only send the D0-exit notification command if D0-state
  * notifications are supported by the EC. Only newer Surface generations
  * support these notifications.
  *
  * Use ssam_ctrl_notif_d0_entry() to reverse the effects of this function.
  *
  * Return: Returns zero on success or if no request has been executed, the
  * status of the executed SAM request if that request failed, or %-EPROTO if
  * an unexpected response has been received.
  */
 int ssam_ctrl_notif_d0_exit(struct ssam_controller *ctrl)
 {
     int status;
     u8 response;
 
     if (!ctrl->caps.d3_closes_handle)
         return 0;
 
     ssam_dbg(ctrl, "pm: notifying D0 exit\n");
 
     status = ssam_retry(ssam_ssh_notif_d0_exit, ctrl, &response);
     if (status)
         return status;
 
     if (response != 0) {
         ssam_err(ctrl, "unexpected response from D0-exit notification: %#04x\n",
              response);
         return -EPROTO;
     }
 
     return 0;
 }
 
 /**
  * ssam_ctrl_notif_d0_entry() - Notify EC that the driver/device enters the D0
  * power state.
  * @ctrl: The controller
  *
  * Notifies the EC that the driver has exited a lower-power state and entered
  * the D0 power state. Exact effects of this function related to the EC are
  * currently unknown.
  *
  * This function will only send the D0-entry notification command if D0-state
  * notifications are supported by the EC. Only newer Surface generations
  * support these notifications.
  *
  * See ssam_ctrl_notif_d0_exit() for more details.
  *
  * Return: Returns zero on success or if no request has been executed, the
  * status of the executed SAM request if that request failed, or %-EPROTO if
  * an unexpected response has been received.
  */
 int ssam_ctrl_notif_d0_entry(struct ssam_controller *ctrl)
 {
     int status;
     u8 response;
 
     if (!ctrl->caps.d3_closes_handle)
         return 0;
 
     ssam_dbg(ctrl, "pm: notifying D0 entry\n");
 
     status = ssam_retry(ssam_ssh_notif_d0_entry, ctrl, &response);
     if (status)
         return status;
 
     if (response != 0) {
         ssam_err(ctrl, "unexpected response from D0-entry notification: %#04x\n",
              response);
         return -EPROTO;
     }
 
     return 0;
 }
 
 
 /* -- Top-level event registry interface. ----------------------------------- */
 
 /**
  * ssam_nf_refcount_enable() - Enable event for reference count entry if it has
  * not already been enabled.
  * @ctrl:  The controller to enable the event on.
  * @entry: The reference count entry for the event to be enabled.
  * @flags: The flags used for enabling the event on the EC.
  *
  * Enable the event associated with the given reference count entry if the
  * reference count equals one, i.e. the event has not previously been enabled.
  * If the event has already been enabled (i.e. reference count not equal to
  * one), check that the flags used for enabling match and warn about this if
  * they do not.
  *
  * This does not modify the reference count itself, which is done with
  * ssam_nf_refcount_inc() / ssam_nf_refcount_dec().
  *
  * Note: ``nf->lock`` must be held when calling this function.
  *
  * Return: Returns zero on success. If the event is enabled by this call,
  * returns the status of the event-enable EC command.
  */
 static int ssam_nf_refcount_enable(struct ssam_controller *ctrl,
                    struct ssam_nf_refcount_entry *entry, u8 flags)
 {
     const struct ssam_event_registry reg = entry->key.reg;
     const struct ssam_event_id id = entry->key.id;
     struct ssam_nf *nf = &ctrl->cplt.event.notif;
     int status;
 
     lockdep_assert_held(&nf->lock);
 
     ssam_dbg(ctrl, "enabling event (reg: %#04x, tc: %#04x, iid: %#04x, rc: %d)\n",
          reg.target_category, id.target_category, id.instance, entry->refcount);
 
     if (entry->refcount == 1) {
         status = ssam_ssh_event_enable(ctrl, reg, id, flags);
         if (status)
             return status;
 
         entry->flags = flags;
 
     } else if (entry->flags != flags) {
         ssam_warn(ctrl,
               "inconsistent flags when enabling event: got %#04x, expected %#04x (reg: %#04x, tc: %#04x, iid: %#04x)\n",
               flags, entry->flags, reg.target_category, id.target_category,
               id.instance);
     }
 
     return 0;
 }
 
 /**
  * ssam_nf_refcount_disable_free() - Disable event for reference count entry if
  * it is no longer in use and free the corresponding entry.
  * @ctrl:  The controller to disable the event on.
  * @entry: The reference count entry for the event to be disabled.
  * @flags: The flags used for enabling the event on the EC.
  * @ec:    Flag specifying if the event should actually be disabled on the EC.
  *
  * If ``ec`` equals ``true`` and the reference count equals zero (i.e. the
  * event is no longer requested by any client), the specified event will be
  * disabled on the EC via the corresponding request.
  *
  * If ``ec`` equals ``false``, no request will be sent to the EC and the event
  * can be considered in a detached state (i.e. no longer used but still
  * enabled). Disabling an event via this method may be required for
  * hot-removable devices, where event disable requests may time out after the
  * device has been physically removed.
  *
  * In both cases, if the reference count equals zero, the corresponding
  * reference count entry will be freed. The reference count entry must not be
  * used any more after a call to this function.
  *
  * Also checks if the flags used for disabling the event match the flags used
  * for enabling the event and warns if they do not (regardless of reference
  * count).
  *
  * This does not modify the reference count itself, which is done with
  * ssam_nf_refcount_inc() / ssam_nf_refcount_dec().
  *
  * Note: ``nf->lock`` must be held when calling this function.
  *
  * Return: Returns zero on success. If the event is disabled by this call,
  * returns the status of the event-enable EC command.
  */
 static int ssam_nf_refcount_disable_free(struct ssam_controller *ctrl,
                      struct ssam_nf_refcount_entry *entry, u8 flags, bool ec)
 {
     const struct ssam_event_registry reg = entry->key.reg;
     const struct ssam_event_id id = entry->key.id;
     struct ssam_nf *nf = &ctrl->cplt.event.notif;
     int status = 0;
 
     lockdep_assert_held(&nf->lock);
 
     ssam_dbg(ctrl, "%s event (reg: %#04x, tc: %#04x, iid: %#04x, rc: %d)\n",
          ec ? "disabling" : "detaching", reg.target_category, id.target_category,
          id.instance, entry->refcount);
 
     if (entry->flags != flags) {
         ssam_warn(ctrl,
               "inconsistent flags when disabling event: got %#04x, expected %#04x (reg: %#04x, tc: %#04x, iid: %#04x)\n",
               flags, entry->flags, reg.target_category, id.target_category,
               id.instance);
     }
 
     if (ec && entry->refcount == 0) {
         status = ssam_ssh_event_disable(ctrl, reg, id, flags);
         kfree(entry);
     }
 
     return status;
 }
 
 /**
  * ssam_notifier_register() - Register an event notifier.
  * @ctrl: The controller to register the notifier on.
  * @n:    The event notifier to register.
  *
  * Register an event notifier. Increment the usage counter of the associated
  * SAM event if the notifier is not marked as an observer. If the event is not
  * marked as an observer and is currently not enabled, it will be enabled
  * during this call. If the notifier is marked as an observer, no attempt will
  * be made at enabling any event and no reference count will be modified.
  *
  * Notifiers marked as observers do not need to be associated with one specific
  * event, i.e. as long as no event matching is performed, only the event target
  * category needs to be set.
  *
  * Return: Returns zero on success, %-ENOSPC if there have already been
  * %INT_MAX notifiers for the event ID/type associated with the notifier block
  * registered, %-ENOMEM if the corresponding event entry could not be
  * allocated. If this is the first time that a notifier block is registered
  * for the specific associated event, returns the status of the event-enable
  * EC-command.
  */
 int ssam_notifier_register(struct ssam_controller *ctrl, struct ssam_event_notifier *n)
 {
     u16 rqid = ssh_tc_to_rqid(n->event.id.target_category);
     struct ssam_nf_refcount_entry *entry = NULL;
     struct ssam_nf_head *nf_head;
     struct ssam_nf *nf;
     int status;
 
     if (!ssh_rqid_is_event(rqid))
         return -EINVAL;
 
     nf = &ctrl->cplt.event.notif;
     nf_head = &nf->head[ssh_rqid_to_event(rqid)];
 
     mutex_lock(&nf->lock);
 
     if (!(n->flags & SSAM_EVENT_NOTIFIER_OBSERVER)) {
         entry = ssam_nf_refcount_inc(nf, n->event.reg, n->event.id);
         if (IS_ERR(entry)) {
             mutex_unlock(&nf->lock);
             return PTR_ERR(entry);
         }
     }
 
     status = ssam_nfblk_insert(nf_head, &n->base);
     if (status) {
         if (entry)
             ssam_nf_refcount_dec_free(nf, n->event.reg, n->event.id);
 
         mutex_unlock(&nf->lock);
         return status;
     }
 
     if (entry) {
         status = ssam_nf_refcount_enable(ctrl, entry, n->event.flags);
         if (status) {
             ssam_nfblk_remove(&n->base);
             ssam_nf_refcount_dec_free(nf, n->event.reg, n->event.id);
             mutex_unlock(&nf->lock);
             synchronize_srcu(&nf_head->srcu);
             return status;
         }
     }
 
     mutex_unlock(&nf->lock);
     return 0;
 }
 EXPORT_SYMBOL_GPL(ssam_notifier_register);
 
 /**
  * __ssam_notifier_unregister() - Unregister an event notifier.
  * @ctrl:    The controller the notifier has been registered on.
  * @n:       The event notifier to unregister.
  * @disable: Whether to disable the corresponding event on the EC.
  *
  * Unregister an event notifier. Decrement the usage counter of the associated
  * SAM event if the notifier is not marked as an observer. If the usage counter
  * reaches zero and ``disable`` equals ``true``, the event will be disabled.
  *
  * Useful for hot-removable devices, where communication may fail once the
  * device has been physically removed. In that case, specifying ``disable`` as
  * ``false`` avoids communication with the EC.
  *
  * Return: Returns zero on success, %-ENOENT if the given notifier block has
  * not been registered on the controller. If the given notifier block was the
  * last one associated with its specific event, returns the status of the
  * event-disable EC-command.
  */
 int __ssam_notifier_unregister(struct ssam_controller *ctrl, struct ssam_event_notifier *n,
                    bool disable)
 {
     u16 rqid = ssh_tc_to_rqid(n->event.id.target_category);
     struct ssam_nf_refcount_entry *entry;
     struct ssam_nf_head *nf_head;
     struct ssam_nf *nf;
     int status = 0;
 
     if (!ssh_rqid_is_event(rqid))
         return -EINVAL;
 
     nf = &ctrl->cplt.event.notif;
     nf_head = &nf->head[ssh_rqid_to_event(rqid)];
 
     mutex_lock(&nf->lock);
 
     if (!ssam_nfblk_find(nf_head, &n->base)) {
         mutex_unlock(&nf->lock);
         return -ENOENT;
     }
 
     /*
      * If this is an observer notifier, do not attempt to disable the
      * event, just remove it.
      */
     if (!(n->flags & SSAM_EVENT_NOTIFIER_OBSERVER)) {
         entry = ssam_nf_refcount_dec(nf, n->event.reg, n->event.id);
         if (WARN_ON(!entry)) {
             /*
              * If this does not return an entry, there's a logic
              * error somewhere: The notifier block is registered,
              * but the event refcount entry is not there. Remove
              * the notifier block anyways.
              */
             status = -ENOENT;
             goto remove;
         }
 
         status = ssam_nf_refcount_disable_free(ctrl, entry, n->event.flags, disable);
     }
 
 remove:
     ssam_nfblk_remove(&n->base);
     mutex_unlock(&nf->lock);
     synchronize_srcu(&nf_head->srcu);
 
     return status;
 }
 EXPORT_SYMBOL_GPL(__ssam_notifier_unregister);
 
 /**
  * ssam_controller_event_enable() - Enable the specified event.
  * @ctrl:  The controller to enable the event for.
  * @reg:   The event registry to use for enabling the event.
  * @id:    The event ID specifying the event to be enabled.
  * @flags: The SAM event flags used for enabling the event.
  *
  * Increment the event reference count of the specified event. If the event has
  * not been enabled previously, it will be enabled by this call.
  *
  * Note: In general, ssam_notifier_register() with a non-observer notifier
  * should be preferred for enabling/disabling events, as this will guarantee
  * proper ordering and event forwarding in case of errors during event
  * enabling/disabling.
  *
  * Return: Returns zero on success, %-ENOSPC if the reference count for the
  * specified event has reached its maximum, %-ENOMEM if the corresponding event
  * entry could not be allocated. If this is the first time that this event has
  * been enabled (i.e. the reference count was incremented from zero to one by
  * this call), returns the status of the event-enable EC-command.
  */
 int ssam_controller_event_enable(struct ssam_controller *ctrl,
                  struct ssam_event_registry reg,
                  struct ssam_event_id id, u8 flags)
 {
     u16 rqid = ssh_tc_to_rqid(id.target_category);
     struct ssam_nf *nf = &ctrl->cplt.event.notif;
     struct ssam_nf_refcount_entry *entry;
     int status;
 
     if (!ssh_rqid_is_event(rqid))
         return -EINVAL;
 
     mutex_lock(&nf->lock);
 
     entry = ssam_nf_refcount_inc(nf, reg, id);
     if (IS_ERR(entry)) {
         mutex_unlock(&nf->lock);
         return PTR_ERR(entry);
     }
 
     status = ssam_nf_refcount_enable(ctrl, entry, flags);
     if (status) {
         ssam_nf_refcount_dec_free(nf, reg, id);
         mutex_unlock(&nf->lock);
         return status;
     }
 
     mutex_unlock(&nf->lock);
     return 0;
 }
 EXPORT_SYMBOL_GPL(ssam_controller_event_enable);
 
 /**
  * ssam_controller_event_disable() - Disable the specified event.
  * @ctrl:  The controller to disable the event for.
  * @reg:   The event registry to use for disabling the event.
  * @id:    The event ID specifying the event to be disabled.
  * @flags: The flags used when enabling the event.
  *
  * Decrement the reference count of the specified event. If the reference count
  * reaches zero, the event will be disabled.
  *
  * Note: In general, ssam_notifier_register()/ssam_notifier_unregister() with a
  * non-observer notifier should be preferred for enabling/disabling events, as
  * this will guarantee proper ordering and event forwarding in case of errors
  * during event enabling/disabling.
  *
  * Return: Returns zero on success, %-ENOENT if the given event has not been
  * enabled on the controller. If the reference count of the event reaches zero
  * during this call, returns the status of the event-disable EC-command.
  */
 int ssam_controller_event_disable(struct ssam_controller *ctrl,
                   struct ssam_event_registry reg,
                   struct ssam_event_id id, u8 flags)
 {
     u16 rqid = ssh_tc_to_rqid(id.target_category);
     struct ssam_nf *nf = &ctrl->cplt.event.notif;
     struct ssam_nf_refcount_entry *entry;
     int status;
 
     if (!ssh_rqid_is_event(rqid))
         return -EINVAL;
 
     mutex_lock(&nf->lock);
 
     entry = ssam_nf_refcount_dec(nf, reg, id);
     if (!entry) {
         mutex_unlock(&nf->lock);
         return -ENOENT;
     }
 
     status = ssam_nf_refcount_disable_free(ctrl, entry, flags, true);
 
     mutex_unlock(&nf->lock);
     return status;
 }
 EXPORT_SYMBOL_GPL(ssam_controller_event_disable);
 
 /**
  * ssam_notifier_disable_registered() - Disable events for all registered
  * notifiers.
  * @ctrl: The controller for which to disable the notifiers/events.
  *
  * Disables events for all currently registered notifiers. In case of an error
  * (EC command failing), all previously disabled events will be restored and
  * the error code returned.
  *
  * This function is intended to disable all events prior to hibernation entry.
  * See ssam_notifier_restore_registered() to restore/re-enable all events
  * disabled with this function.
  *
  * Note that this function will not disable events for notifiers registered
  * after calling this function. It should thus be made sure that no new
  * notifiers are going to be added after this call and before the corresponding
  * call to ssam_notifier_restore_registered().
  *
  * Return: Returns zero on success. In case of failure returns the error code
  * returned by the failed EC command to disable an event.
  */
 int ssam_notifier_disable_registered(struct ssam_controller *ctrl)
 {
     struct ssam_nf *nf = &ctrl->cplt.event.notif;
     struct rb_node *n;
     int status;
 
     mutex_lock(&nf->lock);
     for (n = rb_first(&nf->refcount); n; n = rb_next(n)) {
         struct ssam_nf_refcount_entry *e;
 
         e = rb_entry(n, struct ssam_nf_refcount_entry, node);
         status = ssam_ssh_event_disable(ctrl, e->key.reg,
                         e->key.id, e->flags);
         if (status)
             goto err;
     }
     mutex_unlock(&nf->lock);
 
     return 0;
 
 err:
     for (n = rb_prev(n); n; n = rb_prev(n)) {
         struct ssam_nf_refcount_entry *e;
 
         e = rb_entry(n, struct ssam_nf_refcount_entry, node);
         ssam_ssh_event_enable(ctrl, e->key.reg, e->key.id, e->flags);
     }
     mutex_unlock(&nf->lock);
 
     return status;
 }
 
 /**
  * ssam_notifier_restore_registered() - Restore/re-enable events for all
  * registered notifiers.
  * @ctrl: The controller for which to restore the notifiers/events.
  *
  * Restores/re-enables all events for which notifiers have been registered on
  * the given controller. In case of a failure, the error is logged and the
  * function continues to try and enable the remaining events.
  *
  * This function is intended to restore/re-enable all registered events after
  * hibernation. See ssam_notifier_disable_registered() for the counter part
  * disabling the events and more details.
  */
 void ssam_notifier_restore_registered(struct ssam_controller *ctrl)
 {
     struct ssam_nf *nf = &ctrl->cplt.event.notif;
     struct rb_node *n;
 
     mutex_lock(&nf->lock);
     for (n = rb_first(&nf->refcount); n; n = rb_next(n)) {
         struct ssam_nf_refcount_entry *e;
 
         e = rb_entry(n, struct ssam_nf_refcount_entry, node);
 
         /* Ignore errors, will get logged in call. */
         ssam_ssh_event_enable(ctrl, e->key.reg, e->key.id, e->flags);
     }
     mutex_unlock(&nf->lock);
 }
 
 /**
  * ssam_notifier_is_empty() - Check if there are any registered notifiers.
  * @ctrl: The controller to check on.
  *
  * Return: Returns %true if there are currently no notifiers registered on the
  * controller, %false otherwise.
  */
 static bool ssam_notifier_is_empty(struct ssam_controller *ctrl)
 {
     struct ssam_nf *nf = &ctrl->cplt.event.notif;
     bool result;
 
     mutex_lock(&nf->lock);
     result = ssam_nf_refcount_empty(nf);
     mutex_unlock(&nf->lock);
 
     return result;
 }
 
 /**
  * ssam_notifier_unregister_all() - Unregister all currently registered
  * notifiers.
  * @ctrl: The controller to unregister the notifiers on.
  *
  * Unregisters all currently registered notifiers. This function is used to
  * ensure that all notifiers will be unregistered and associated
  * entries/resources freed when the controller is being shut down.
  */
 static void ssam_notifier_unregister_all(struct ssam_controller *ctrl)
 {
     struct ssam_nf *nf = &ctrl->cplt.event.notif;
     struct ssam_nf_refcount_entry *e, *n;
 
     mutex_lock(&nf->lock);
     rbtree_postorder_for_each_entry_safe(e, n, &nf->refcount, node) {
         /* Ignore errors, will get logged in call. */
         ssam_ssh_event_disable(ctrl, e->key.reg, e->key.id, e->flags);
         kfree(e);
     }
     nf->refcount = RB_ROOT;
     mutex_unlock(&nf->lock);
 }
 
 
 /* -- Wakeup IRQ. ----------------------------------------------------------- */
 
 static irqreturn_t ssam_irq_handle(int irq, void *dev_id)
 {
     struct ssam_controller *ctrl = dev_id;
 
     ssam_dbg(ctrl, "pm: wake irq triggered\n");
 
     /*
      * Note: Proper wakeup detection is currently unimplemented.
      *       When the EC is in display-off or any other non-D0 state, it
      *       does not send events/notifications to the host. Instead it
      *       signals that there are events available via the wakeup IRQ.
      *       This driver is responsible for calling back to the EC to
      *       release these events one-by-one.
      *
      *       This IRQ should not cause a full system resume by its own.
      *       Instead, events should be handled by their respective subsystem
      *       drivers, which in turn should signal whether a full system
      *       resume should be performed.
      *
      * TODO: Send GPIO callback command repeatedly to EC until callback
      *       returns 0x00. Return flag of callback is "has more events".
      *       Each time the command is sent, one event is "released". Once
      *       all events have been released (return = 0x00), the GPIO is
      *       re-armed. Detect wakeup events during this process, go back to
      *       sleep if no wakeup event has been received.
      */
 
     return IRQ_HANDLED;
 }
 
 /**
  * ssam_irq_setup() - Set up SAM EC wakeup-GPIO interrupt.
  * @ctrl: The controller for which the IRQ should be set up.
  *
  * Set up an IRQ for the wakeup-GPIO pin of the SAM EC. This IRQ can be used
  * to wake the device from a low power state.
  *
  * Note that this IRQ can only be triggered while the EC is in the display-off
  * state. In this state, events are not sent to the host in the usual way.
  * Instead the wakeup-GPIO gets pulled to "high" as long as there are pending
  * events and these events need to be released one-by-one via the GPIO
  * callback request, either until there are no events left and the GPIO is
  * reset, or all at once by transitioning the EC out of the display-off state,
  * which will also clear the GPIO.
  *
  * Not all events, however, should trigger a full system wakeup. Instead the
  * driver should, if necessary, inspect and forward each event to the
  * corresponding subsystem, which in turn should decide if the system needs to
  * be woken up. This logic has not been implemented yet, thus wakeup by this
  * IRQ should be disabled by default to avoid spurious wake-ups, caused, for
  * example, by the remaining battery percentage changing. Refer to comments in
  * this function and comments in the corresponding IRQ handler for more
  * details on how this should be implemented.
  *
  * See also ssam_ctrl_notif_display_off() and ssam_ctrl_notif_display_off()
  * for functions to transition the EC into and out of the display-off state as
  * well as more details on it.
  *
  * The IRQ is disabled by default and has to be enabled before it can wake up
  * the device from suspend via ssam_irq_arm_for_wakeup(). On teardown, the IRQ
  * should be freed via ssam_irq_free().
  */
 int ssam_irq_setup(struct ssam_controller *ctrl)
 {
     struct device *dev = ssam_controller_device(ctrl);
     struct gpio_desc *gpiod;
     int irq;
     int status;
 
     /*
      * The actual GPIO interrupt is declared in ACPI as TRIGGER_HIGH.
      * However, the GPIO line only gets reset by sending the GPIO callback
      * command to SAM (or alternatively the display-on notification). As
      * proper handling for this interrupt is not implemented yet, leaving
      * the IRQ at TRIGGER_HIGH would cause an IRQ storm (as the callback
      * never gets sent and thus the line never gets reset). To avoid this,
      * mark the IRQ as TRIGGER_RISING for now, only creating a single
      * interrupt, and let the SAM resume callback during the controller
      * resume process clear it.
      */
     const int irqf = IRQF_ONESHOT | IRQF_TRIGGER_RISING | IRQF_NO_AUTOEN;
 
     gpiod = gpiod_get(dev, "ssam_wakeup-int", GPIOD_ASIS);
     if (IS_ERR(gpiod))
         return PTR_ERR(gpiod);
 
     irq = gpiod_to_irq(gpiod);
     gpiod_put(gpiod);
 
     if (irq < 0)
         return irq;
 
     status = request_threaded_irq(irq, NULL, ssam_irq_handle, irqf,
                       "ssam_wakeup", ctrl);
     if (status)
         return status;
 
     ctrl->irq.num = irq;
     return 0;
 }
 
 /**
  * ssam_irq_free() - Free SAM EC wakeup-GPIO interrupt.
  * @ctrl: The controller for which the IRQ should be freed.
  *
  * Free the wakeup-GPIO IRQ previously set-up via ssam_irq_setup().
  */
 void ssam_irq_free(struct ssam_controller *ctrl)
 {
     free_irq(ctrl->irq.num, ctrl);
     ctrl->irq.num = -1;
 }
 
 /**
  * ssam_irq_arm_for_wakeup() - Arm the EC IRQ for wakeup, if enabled.
  * @ctrl: The controller for which the IRQ should be armed.
  *
  * Sets up the IRQ so that it can be used to wake the device. Specifically,
  * this function enables the irq and then, if the device is allowed to wake up
  * the system, calls enable_irq_wake(). See ssam_irq_disarm_wakeup() for the
  * corresponding function to disable the IRQ.
  *
  * This function is intended to arm the IRQ before entering S2idle suspend.
  *
  * Note: calls to ssam_irq_arm_for_wakeup() and ssam_irq_disarm_wakeup() must
  * be balanced.
  */
 int ssam_irq_arm_for_wakeup(struct ssam_controller *ctrl)
 {
     struct device *dev = ssam_controller_device(ctrl);
     int status;
 
     enable_irq(ctrl->irq.num);
     if (device_may_wakeup(dev)) {
         status = enable_irq_wake(ctrl->irq.num);
         if (status) {
             ssam_err(ctrl, "failed to enable wake IRQ: %d\n", status);
             disable_irq(ctrl->irq.num);
             return status;
         }
 
         ctrl->irq.wakeup_enabled = true;
     } else {
         ctrl->irq.wakeup_enabled = false;
     }
 
     return 0;
 }
 
 /**
  * ssam_irq_disarm_wakeup() - Disarm the wakeup IRQ.
  * @ctrl: The controller for which the IRQ should be disarmed.
  *
  * Disarm the IRQ previously set up for wake via ssam_irq_arm_for_wakeup().
  *
  * This function is intended to disarm the IRQ after exiting S2idle suspend.
  *
  * Note: calls to ssam_irq_arm_for_wakeup() and ssam_irq_disarm_wakeup() must
  * be balanced.
  */
 void ssam_irq_disarm_wakeup(struct ssam_controller *ctrl)
 {
     int status;
 
     if (ctrl->irq.wakeup_enabled) {
         status = disable_irq_wake(ctrl->irq.num);
         if (status)
             ssam_err(ctrl, "failed to disable wake IRQ: %d\n", status);
 
         ctrl->irq.wakeup_enabled = false;
     }
     disable_irq(ctrl->irq.num);
 }

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