OSCL-LXR linux-6.0.1/​drivers/​rpmsg/​virtio_rpmsg_bus.c	Source navigation Diff markup Identifier search General search
	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
 /*
  * Virtio-based remote processor messaging bus
  *
  * Copyright (C) 2011 Texas Instruments, Inc.
  * Copyright (C) 2011 Google, Inc.
  *
  * Ohad Ben-Cohen <ohad@wizery.com>
  * Brian Swetland <swetland@google.com>
  */
 
 #define pr_fmt(fmt) "%s: " fmt, __func__
 
 #include <linux/dma-mapping.h>
 #include <linux/idr.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/rpmsg.h>
 #include <linux/rpmsg/byteorder.h>
 #include <linux/rpmsg/ns.h>
 #include <linux/scatterlist.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/virtio.h>
 #include <linux/virtio_ids.h>
 #include <linux/virtio_config.h>
 #include <linux/wait.h>
 
 #include "rpmsg_internal.h"
 
 /**
  * struct virtproc_info - virtual remote processor state
  * @vdev:   the virtio device
  * @rvq:    rx virtqueue
  * @svq:    tx virtqueue
  * @rbufs:  kernel address of rx buffers
  * @sbufs:  kernel address of tx buffers
  * @num_bufs:   total number of buffers for rx and tx
  * @buf_size:   size of one rx or tx buffer
  * @last_sbuf:  index of last tx buffer used
  * @bufs_dma:   dma base addr of the buffers
  * @tx_lock:    protects svq, sbufs and sleepers, to allow concurrent senders.
  *      sending a message might require waking up a dozing remote
  *      processor, which involves sleeping, hence the mutex.
  * @endpoints:  idr of local endpoints, allows fast retrieval
  * @endpoints_lock: lock of the endpoints set
  * @sendq:  wait queue of sending contexts waiting for a tx buffers
  * @sleepers:   number of senders that are waiting for a tx buffer
  *
  * This structure stores the rpmsg state of a given virtio remote processor
  * device (there might be several virtio proc devices for each physical
  * remote processor).
  */
 struct virtproc_info {
     struct virtio_device *vdev;
     struct virtqueue *rvq, *svq;
     void *rbufs, *sbufs;
     unsigned int num_bufs;
     unsigned int buf_size;
     int last_sbuf;
     dma_addr_t bufs_dma;
     struct mutex tx_lock;
     struct idr endpoints;
     struct mutex endpoints_lock;
     wait_queue_head_t sendq;
     atomic_t sleepers;
 };
 
 /* The feature bitmap for virtio rpmsg */
 #define VIRTIO_RPMSG_F_NS   0 /* RP supports name service notifications */
 
 /**
  * struct rpmsg_hdr - common header for all rpmsg messages
  * @src: source address
  * @dst: destination address
  * @reserved: reserved for future use
  * @len: length of payload (in bytes)
  * @flags: message flags
  * @data: @len bytes of message payload data
  *
  * Every message sent(/received) on the rpmsg bus begins with this header.
  */
 struct rpmsg_hdr {
     __rpmsg32 src;
     __rpmsg32 dst;
     __rpmsg32 reserved;
     __rpmsg16 len;
     __rpmsg16 flags;
     u8 data[];
 } __packed;
 
 
 /**
  * struct virtio_rpmsg_channel - rpmsg channel descriptor
  * @rpdev: the rpmsg channel device
  * @vrp: the virtio remote processor device this channel belongs to
  *
  * This structure stores the channel that links the rpmsg device to the virtio
  * remote processor device.
  */
 struct virtio_rpmsg_channel {
     struct rpmsg_device rpdev;
 
     struct virtproc_info *vrp;
 };
 
 #define to_virtio_rpmsg_channel(_rpdev) \
     container_of(_rpdev, struct virtio_rpmsg_channel, rpdev)
 
 /*
  * We're allocating buffers of 512 bytes each for communications. The
  * number of buffers will be computed from the number of buffers supported
  * by the vring, upto a maximum of 512 buffers (256 in each direction).
  *
  * Each buffer will have 16 bytes for the msg header and 496 bytes for
  * the payload.
  *
  * This will utilize a maximum total space of 256KB for the buffers.
  *
  * We might also want to add support for user-provided buffers in time.
  * This will allow bigger buffer size flexibility, and can also be used
  * to achieve zero-copy messaging.
  *
  * Note that these numbers are purely a decision of this driver - we
  * can change this without changing anything in the firmware of the remote
  * processor.
  */
 #define MAX_RPMSG_NUM_BUFS  (512)
 #define MAX_RPMSG_BUF_SIZE  (512)
 
 /*
  * Local addresses are dynamically allocated on-demand.
  * We do not dynamically assign addresses from the low 1024 range,
  * in order to reserve that address range for predefined services.
  */
 #define RPMSG_RESERVED_ADDRESSES    (1024)
 
 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
                    u32 dst);
 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
                     u32 dst, void *data, int len);
 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len);
 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
                   int len, u32 dst);
 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
                        u32 dst, void *data, int len);
 static ssize_t virtio_rpmsg_get_mtu(struct rpmsg_endpoint *ept);
 static struct rpmsg_device *__rpmsg_create_channel(struct virtproc_info *vrp,
                            struct rpmsg_channel_info *chinfo);
 
 static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
     .destroy_ept = virtio_rpmsg_destroy_ept,
     .send = virtio_rpmsg_send,
     .sendto = virtio_rpmsg_sendto,
     .send_offchannel = virtio_rpmsg_send_offchannel,
     .trysend = virtio_rpmsg_trysend,
     .trysendto = virtio_rpmsg_trysendto,
     .trysend_offchannel = virtio_rpmsg_trysend_offchannel,
     .get_mtu = virtio_rpmsg_get_mtu,
 };
 
 /**
  * rpmsg_sg_init - initialize scatterlist according to cpu address location
  * @sg: scatterlist to fill
  * @cpu_addr: virtual address of the buffer
  * @len: buffer length
  *
  * An internal function filling scatterlist according to virtual address
  * location (in vmalloc or in kernel).
  */
 static void
 rpmsg_sg_init(struct scatterlist *sg, void *cpu_addr, unsigned int len)
 {
     if (is_vmalloc_addr(cpu_addr)) {
         sg_init_table(sg, 1);
         sg_set_page(sg, vmalloc_to_page(cpu_addr), len,
                 offset_in_page(cpu_addr));
     } else {
         WARN_ON(!virt_addr_valid(cpu_addr));
         sg_init_one(sg, cpu_addr, len);
     }
 }
 
 /**
  * __ept_release() - deallocate an rpmsg endpoint
  * @kref: the ept's reference count
  *
  * This function deallocates an ept, and is invoked when its @kref refcount
  * drops to zero.
  *
  * Never invoke this function directly!
  */
 static void __ept_release(struct kref *kref)
 {
     struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
                           refcount);
     /*
      * At this point no one holds a reference to ept anymore,
      * so we can directly free it
      */
     kfree(ept);
 }
 
 /* for more info, see below documentation of rpmsg_create_ept() */
 static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
                          struct rpmsg_device *rpdev,
                          rpmsg_rx_cb_t cb,
                          void *priv, u32 addr)
 {
     int id_min, id_max, id;
     struct rpmsg_endpoint *ept;
     struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
 
     ept = kzalloc(sizeof(*ept), GFP_KERNEL);
     if (!ept)
         return NULL;
 
     kref_init(&ept->refcount);
     mutex_init(&ept->cb_lock);
 
     ept->rpdev = rpdev;
     ept->cb = cb;
     ept->priv = priv;
     ept->ops = &virtio_endpoint_ops;
 
     /* do we need to allocate a local address ? */
     if (addr == RPMSG_ADDR_ANY) {
         id_min = RPMSG_RESERVED_ADDRESSES;
         id_max = 0;
     } else {
         id_min = addr;
         id_max = addr + 1;
     }
 
     mutex_lock(&vrp->endpoints_lock);
 
     /* bind the endpoint to an rpmsg address (and allocate one if needed) */
     id = idr_alloc(&vrp->endpoints, ept, id_min, id_max, GFP_KERNEL);
     if (id < 0) {
         dev_err(dev, "idr_alloc failed: %d\n", id);
         goto free_ept;
     }
     ept->addr = id;
 
     mutex_unlock(&vrp->endpoints_lock);
 
     return ept;
 
 free_ept:
     mutex_unlock(&vrp->endpoints_lock);
     kref_put(&ept->refcount, __ept_release);
     return NULL;
 }
 
 static struct rpmsg_device *virtio_rpmsg_create_channel(struct rpmsg_device *rpdev,
                             struct rpmsg_channel_info *chinfo)
 {
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
     struct virtproc_info *vrp = vch->vrp;
 
     return __rpmsg_create_channel(vrp, chinfo);
 }
 
 static int virtio_rpmsg_release_channel(struct rpmsg_device *rpdev,
                     struct rpmsg_channel_info *chinfo)
 {
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
     struct virtproc_info *vrp = vch->vrp;
 
     return rpmsg_unregister_device(&vrp->vdev->dev, chinfo);
 }
 
 static struct rpmsg_endpoint *virtio_rpmsg_create_ept(struct rpmsg_device *rpdev,
                               rpmsg_rx_cb_t cb,
                               void *priv,
                               struct rpmsg_channel_info chinfo)
 {
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 
     return __rpmsg_create_ept(vch->vrp, rpdev, cb, priv, chinfo.src);
 }
 
 /**
  * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
  * @vrp: virtproc which owns this ept
  * @ept: endpoing to destroy
  *
  * An internal function which destroy an ept without assuming it is
  * bound to an rpmsg channel. This is needed for handling the internal
  * name service endpoint, which isn't bound to an rpmsg channel.
  * See also __rpmsg_create_ept().
  */
 static void
 __rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
 {
     /* make sure new inbound messages can't find this ept anymore */
     mutex_lock(&vrp->endpoints_lock);
     idr_remove(&vrp->endpoints, ept->addr);
     mutex_unlock(&vrp->endpoints_lock);
 
     /* make sure in-flight inbound messages won't invoke cb anymore */
     mutex_lock(&ept->cb_lock);
     ept->cb = NULL;
     mutex_unlock(&ept->cb_lock);
 
     kref_put(&ept->refcount, __ept_release);
 }
 
 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
 {
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(ept->rpdev);
 
     __rpmsg_destroy_ept(vch->vrp, ept);
 }
 
 static int virtio_rpmsg_announce_create(struct rpmsg_device *rpdev)
 {
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
     struct virtproc_info *vrp = vch->vrp;
     struct device *dev = &rpdev->dev;
     int err = 0;
 
     /* need to tell remote processor's name service about this channel ? */
     if (rpdev->announce && rpdev->ept &&
         virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
         struct rpmsg_ns_msg nsm;
 
         strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
         nsm.addr = cpu_to_rpmsg32(rpdev, rpdev->ept->addr);
         nsm.flags = cpu_to_rpmsg32(rpdev, RPMSG_NS_CREATE);
 
         err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
         if (err)
             dev_err(dev, "failed to announce service %d\n", err);
     }
 
     return err;
 }
 
 static int virtio_rpmsg_announce_destroy(struct rpmsg_device *rpdev)
 {
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
     struct virtproc_info *vrp = vch->vrp;
     struct device *dev = &rpdev->dev;
     int err = 0;
 
     /* tell remote processor's name service we're removing this channel */
     if (rpdev->announce && rpdev->ept &&
         virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
         struct rpmsg_ns_msg nsm;
 
         strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
         nsm.addr = cpu_to_rpmsg32(rpdev, rpdev->ept->addr);
         nsm.flags = cpu_to_rpmsg32(rpdev, RPMSG_NS_DESTROY);
 
         err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
         if (err)
             dev_err(dev, "failed to announce service %d\n", err);
     }
 
     return err;
 }
 
 static const struct rpmsg_device_ops virtio_rpmsg_ops = {
     .create_channel = virtio_rpmsg_create_channel,
     .release_channel = virtio_rpmsg_release_channel,
     .create_ept = virtio_rpmsg_create_ept,
     .announce_create = virtio_rpmsg_announce_create,
     .announce_destroy = virtio_rpmsg_announce_destroy,
 };
 
 static void virtio_rpmsg_release_device(struct device *dev)
 {
     struct rpmsg_device *rpdev = to_rpmsg_device(dev);
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 
     kfree(vch);
 }
 
 /*
  * create an rpmsg channel using its name and address info.
  * this function will be used to create both static and dynamic
  * channels.
  */
 static struct rpmsg_device *__rpmsg_create_channel(struct virtproc_info *vrp,
                            struct rpmsg_channel_info *chinfo)
 {
     struct virtio_rpmsg_channel *vch;
     struct rpmsg_device *rpdev;
     struct device *tmp, *dev = &vrp->vdev->dev;
     int ret;
 
     /* make sure a similar channel doesn't already exist */
     tmp = rpmsg_find_device(dev, chinfo);
     if (tmp) {
         /* decrement the matched device's refcount back */
         put_device(tmp);
         dev_err(dev, "channel %s:%x:%x already exist\n",
                 chinfo->name, chinfo->src, chinfo->dst);
         return NULL;
     }
 
     vch = kzalloc(sizeof(*vch), GFP_KERNEL);
     if (!vch)
         return NULL;
 
     /* Link the channel to our vrp */
     vch->vrp = vrp;
 
     /* Assign public information to the rpmsg_device */
     rpdev = &vch->rpdev;
     rpdev->src = chinfo->src;
     rpdev->dst = chinfo->dst;
     rpdev->ops = &virtio_rpmsg_ops;
     rpdev->little_endian = virtio_is_little_endian(vrp->vdev);
 
     /*
      * rpmsg server channels has predefined local address (for now),
      * and their existence needs to be announced remotely
      */
     rpdev->announce = rpdev->src != RPMSG_ADDR_ANY;
 
     strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
 
     rpdev->dev.parent = &vrp->vdev->dev;
     rpdev->dev.release = virtio_rpmsg_release_device;
     ret = rpmsg_register_device(rpdev);
     if (ret)
         return NULL;
 
     return rpdev;
 }
 
 /* super simple buffer "allocator" that is just enough for now */
 static void *get_a_tx_buf(struct virtproc_info *vrp)
 {
     unsigned int len;
     void *ret;
 
     /* support multiple concurrent senders */
     mutex_lock(&vrp->tx_lock);
 
     /*
      * either pick the next unused tx buffer
      * (half of our buffers are used for sending messages)
      */
     if (vrp->last_sbuf < vrp->num_bufs / 2)
         ret = vrp->sbufs + vrp->buf_size * vrp->last_sbuf++;
     /* or recycle a used one */
     else
         ret = virtqueue_get_buf(vrp->svq, &len);
 
     mutex_unlock(&vrp->tx_lock);
 
     return ret;
 }
 
 /**
  * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
  * @vrp: virtual remote processor state
  *
  * This function is called before a sender is blocked, waiting for
  * a tx buffer to become available.
  *
  * If we already have blocking senders, this function merely increases
  * the "sleepers" reference count, and exits.
  *
  * Otherwise, if this is the first sender to block, we also enable
  * virtio's tx callbacks, so we'd be immediately notified when a tx
  * buffer is consumed (we rely on virtio's tx callback in order
  * to wake up sleeping senders as soon as a tx buffer is used by the
  * remote processor).
  */
 static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
 {
     /* support multiple concurrent senders */
     mutex_lock(&vrp->tx_lock);
 
     /* are we the first sleeping context waiting for tx buffers ? */
     if (atomic_inc_return(&vrp->sleepers) == 1)
         /* enable "tx-complete" interrupts before dozing off */
         virtqueue_enable_cb(vrp->svq);
 
     mutex_unlock(&vrp->tx_lock);
 }
 
 /**
  * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
  * @vrp: virtual remote processor state
  *
  * This function is called after a sender, that waited for a tx buffer
  * to become available, is unblocked.
  *
  * If we still have blocking senders, this function merely decreases
  * the "sleepers" reference count, and exits.
  *
  * Otherwise, if there are no more blocking senders, we also disable
  * virtio's tx callbacks, to avoid the overhead incurred with handling
  * those (now redundant) interrupts.
  */
 static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
 {
     /* support multiple concurrent senders */
     mutex_lock(&vrp->tx_lock);
 
     /* are we the last sleeping context waiting for tx buffers ? */
     if (atomic_dec_and_test(&vrp->sleepers))
         /* disable "tx-complete" interrupts */
         virtqueue_disable_cb(vrp->svq);
 
     mutex_unlock(&vrp->tx_lock);
 }
 
 /**
  * rpmsg_send_offchannel_raw() - send a message across to the remote processor
  * @rpdev: the rpmsg channel
  * @src: source address
  * @dst: destination address
  * @data: payload of message
  * @len: length of payload
  * @wait: indicates whether caller should block in case no TX buffers available
  *
  * This function is the base implementation for all of the rpmsg sending API.
  *
  * It will send @data of length @len to @dst, and say it's from @src. The
  * message will be sent to the remote processor which the @rpdev channel
  * belongs to.
  *
  * The message is sent using one of the TX buffers that are available for
  * communication with this remote processor.
  *
  * If @wait is true, the caller will be blocked until either a TX buffer is
  * available, or 15 seconds elapses (we don't want callers to
  * sleep indefinitely due to misbehaving remote processors), and in that
  * case -ERESTARTSYS is returned. The number '15' itself was picked
  * arbitrarily; there's little point in asking drivers to provide a timeout
  * value themselves.
  *
  * Otherwise, if @wait is false, and there are no TX buffers available,
  * the function will immediately fail, and -ENOMEM will be returned.
  *
  * Normally drivers shouldn't use this function directly; instead, drivers
  * should use the appropriate rpmsg_{try}send{to, _offchannel} API
  * (see include/linux/rpmsg.h).
  *
  * Return: 0 on success and an appropriate error value on failure.
  */
 static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
                      u32 src, u32 dst,
                      void *data, int len, bool wait)
 {
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
     struct virtproc_info *vrp = vch->vrp;
     struct device *dev = &rpdev->dev;
     struct scatterlist sg;
     struct rpmsg_hdr *msg;
     int err;
 
     /* bcasting isn't allowed */
     if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
         dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
         return -EINVAL;
     }
 
     /*
      * We currently use fixed-sized buffers, and therefore the payload
      * length is limited.
      *
      * One of the possible improvements here is either to support
      * user-provided buffers (and then we can also support zero-copy
      * messaging), or to improve the buffer allocator, to support
      * variable-length buffer sizes.
      */
     if (len > vrp->buf_size - sizeof(struct rpmsg_hdr)) {
         dev_err(dev, "message is too big (%d)\n", len);
         return -EMSGSIZE;
     }
 
     /* grab a buffer */
     msg = get_a_tx_buf(vrp);
     if (!msg && !wait)
         return -ENOMEM;
 
     /* no free buffer ? wait for one (but bail after 15 seconds) */
     while (!msg) {
         /* enable "tx-complete" interrupts, if not already enabled */
         rpmsg_upref_sleepers(vrp);
 
         /*
          * sleep until a free buffer is available or 15 secs elapse.
          * the timeout period is not configurable because there's
          * little point in asking drivers to specify that.
          * if later this happens to be required, it'd be easy to add.
          */
         err = wait_event_interruptible_timeout(vrp->sendq,
                     (msg = get_a_tx_buf(vrp)),
                     msecs_to_jiffies(15000));
 
         /* disable "tx-complete" interrupts if we're the last sleeper */
         rpmsg_downref_sleepers(vrp);
 
         /* timeout ? */
         if (!err) {
             dev_err(dev, "timeout waiting for a tx buffer\n");
             return -ERESTARTSYS;
         }
     }
 
     msg->len = cpu_to_rpmsg16(rpdev, len);
     msg->flags = 0;
     msg->src = cpu_to_rpmsg32(rpdev, src);
     msg->dst = cpu_to_rpmsg32(rpdev, dst);
     msg->reserved = 0;
     memcpy(msg->data, data, len);
 
     dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
         src, dst, len, msg->flags, msg->reserved);
 #if defined(CONFIG_DYNAMIC_DEBUG)
     dynamic_hex_dump("rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
              msg, sizeof(*msg) + len, true);
 #endif
 
     rpmsg_sg_init(&sg, msg, sizeof(*msg) + len);
 
     mutex_lock(&vrp->tx_lock);
 
     /* add message to the remote processor's virtqueue */
     err = virtqueue_add_outbuf(vrp->svq, &sg, 1, msg, GFP_KERNEL);
     if (err) {
         /*
          * need to reclaim the buffer here, otherwise it's lost
          * (memory won't leak, but rpmsg won't use it again for TX).
          * this will wait for a buffer management overhaul.
          */
         dev_err(dev, "virtqueue_add_outbuf failed: %d\n", err);
         goto out;
     }
 
     /* tell the remote processor it has a pending message to read */
     virtqueue_kick(vrp->svq);
 out:
     mutex_unlock(&vrp->tx_lock);
     return err;
 }
 
 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
 {
     struct rpmsg_device *rpdev = ept->rpdev;
     u32 src = ept->addr, dst = rpdev->dst;
 
     return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
 }
 
 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
                    u32 dst)
 {
     struct rpmsg_device *rpdev = ept->rpdev;
     u32 src = ept->addr;
 
     return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
 }
 
 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
                     u32 dst, void *data, int len)
 {
     struct rpmsg_device *rpdev = ept->rpdev;
 
     return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
 }
 
 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
 {
     struct rpmsg_device *rpdev = ept->rpdev;
     u32 src = ept->addr, dst = rpdev->dst;
 
     return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
 }
 
 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
                   int len, u32 dst)
 {
     struct rpmsg_device *rpdev = ept->rpdev;
     u32 src = ept->addr;
 
     return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
 }
 
 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
                        u32 dst, void *data, int len)
 {
     struct rpmsg_device *rpdev = ept->rpdev;
 
     return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
 }
 
 static ssize_t virtio_rpmsg_get_mtu(struct rpmsg_endpoint *ept)
 {
     struct rpmsg_device *rpdev = ept->rpdev;
     struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 
     return vch->vrp->buf_size - sizeof(struct rpmsg_hdr);
 }
 
 static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
                  struct rpmsg_hdr *msg, unsigned int len)
 {
     struct rpmsg_endpoint *ept;
     struct scatterlist sg;
     bool little_endian = virtio_is_little_endian(vrp->vdev);
     unsigned int msg_len = __rpmsg16_to_cpu(little_endian, msg->len);
     int err;
 
     dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
         __rpmsg32_to_cpu(little_endian, msg->src),
         __rpmsg32_to_cpu(little_endian, msg->dst), msg_len,
         __rpmsg16_to_cpu(little_endian, msg->flags),
         __rpmsg32_to_cpu(little_endian, msg->reserved));
 #if defined(CONFIG_DYNAMIC_DEBUG)
     dynamic_hex_dump("rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
              msg, sizeof(*msg) + msg_len, true);
 #endif
 
     /*
      * We currently use fixed-sized buffers, so trivially sanitize
      * the reported payload length.
      */
     if (len > vrp->buf_size ||
         msg_len > (len - sizeof(struct rpmsg_hdr))) {
         dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg_len);
         return -EINVAL;
     }
 
     /* use the dst addr to fetch the callback of the appropriate user */
     mutex_lock(&vrp->endpoints_lock);
 
     ept = idr_find(&vrp->endpoints, __rpmsg32_to_cpu(little_endian, msg->dst));
 
     /* let's make sure no one deallocates ept while we use it */
     if (ept)
         kref_get(&ept->refcount);
 
     mutex_unlock(&vrp->endpoints_lock);
 
     if (ept) {
         /* make sure ept->cb doesn't go away while we use it */
         mutex_lock(&ept->cb_lock);
 
         if (ept->cb)
             ept->cb(ept->rpdev, msg->data, msg_len, ept->priv,
                 __rpmsg32_to_cpu(little_endian, msg->src));
 
         mutex_unlock(&ept->cb_lock);
 
         /* farewell, ept, we don't need you anymore */
         kref_put(&ept->refcount, __ept_release);
     } else
         dev_warn_ratelimited(dev, "msg received with no recipient\n");
 
     /* publish the real size of the buffer */
     rpmsg_sg_init(&sg, msg, vrp->buf_size);
 
     /* add the buffer back to the remote processor's virtqueue */
     err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, msg, GFP_KERNEL);
     if (err < 0) {
         dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
         return err;
     }
 
     return 0;
 }
 
 /* called when an rx buffer is used, and it's time to digest a message */
 static void rpmsg_recv_done(struct virtqueue *rvq)
 {
     struct virtproc_info *vrp = rvq->vdev->priv;
     struct device *dev = &rvq->vdev->dev;
     struct rpmsg_hdr *msg;
     unsigned int len, msgs_received = 0;
     int err;
 
     msg = virtqueue_get_buf(rvq, &len);
     if (!msg) {
         dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
         return;
     }
 
     while (msg) {
         err = rpmsg_recv_single(vrp, dev, msg, len);
         if (err)
             break;
 
         msgs_received++;
 
         msg = virtqueue_get_buf(rvq, &len);
     }
 
     dev_dbg(dev, "Received %u messages\n", msgs_received);
 
     /* tell the remote processor we added another available rx buffer */
     if (msgs_received)
         virtqueue_kick(vrp->rvq);
 }
 
 /*
  * This is invoked whenever the remote processor completed processing
  * a TX msg we just sent it, and the buffer is put back to the used ring.
  *
  * Normally, though, we suppress this "tx complete" interrupt in order to
  * avoid the incurred overhead.
  */
 static void rpmsg_xmit_done(struct virtqueue *svq)
 {
     struct virtproc_info *vrp = svq->vdev->priv;
 
     dev_dbg(&svq->vdev->dev, "%s\n", __func__);
 
     /* wake up potential senders that are waiting for a tx buffer */
     wake_up_interruptible(&vrp->sendq);
 }
 
 /*
  * Called to expose to user a /dev/rpmsg_ctrlX interface allowing to
  * create endpoint-to-endpoint communication without associated RPMsg channel.
  * The endpoints are rattached to the ctrldev RPMsg device.
  */
 static struct rpmsg_device *rpmsg_virtio_add_ctrl_dev(struct virtio_device *vdev)
 {
     struct virtproc_info *vrp = vdev->priv;
     struct virtio_rpmsg_channel *vch;
     struct rpmsg_device *rpdev_ctrl;
     int err = 0;
 
     vch = kzalloc(sizeof(*vch), GFP_KERNEL);
     if (!vch)
         return ERR_PTR(-ENOMEM);
 
     /* Link the channel to the vrp */
     vch->vrp = vrp;
 
     /* Assign public information to the rpmsg_device */
     rpdev_ctrl = &vch->rpdev;
     rpdev_ctrl->ops = &virtio_rpmsg_ops;
 
     rpdev_ctrl->dev.parent = &vrp->vdev->dev;
     rpdev_ctrl->dev.release = virtio_rpmsg_release_device;
     rpdev_ctrl->little_endian = virtio_is_little_endian(vrp->vdev);
 
     err = rpmsg_ctrldev_register_device(rpdev_ctrl);
     if (err) {
         /* vch will be free in virtio_rpmsg_release_device() */
         return ERR_PTR(err);
     }
 
     return rpdev_ctrl;
 }
 
 static void rpmsg_virtio_del_ctrl_dev(struct rpmsg_device *rpdev_ctrl)
 {
     if (!rpdev_ctrl)
         return;
     device_unregister(&rpdev_ctrl->dev);
 }
 
 static int rpmsg_probe(struct virtio_device *vdev)
 {
     vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
     static const char * const names[] = { "input", "output" };
     struct virtqueue *vqs[2];
     struct virtproc_info *vrp;
     struct virtio_rpmsg_channel *vch = NULL;
     struct rpmsg_device *rpdev_ns, *rpdev_ctrl;
     void *bufs_va;
     int err = 0, i;
     size_t total_buf_space;
     bool notify;
 
     vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
     if (!vrp)
         return -ENOMEM;
 
     vrp->vdev = vdev;
 
     idr_init(&vrp->endpoints);
     mutex_init(&vrp->endpoints_lock);
     mutex_init(&vrp->tx_lock);
     init_waitqueue_head(&vrp->sendq);
 
     /* We expect two virtqueues, rx and tx (and in this order) */
     err = virtio_find_vqs(vdev, 2, vqs, vq_cbs, names, NULL);
     if (err)
         goto free_vrp;
 
     vrp->rvq = vqs[0];
     vrp->svq = vqs[1];
 
     /* we expect symmetric tx/rx vrings */
     WARN_ON(virtqueue_get_vring_size(vrp->rvq) !=
         virtqueue_get_vring_size(vrp->svq));
 
     /* we need less buffers if vrings are small */
     if (virtqueue_get_vring_size(vrp->rvq) < MAX_RPMSG_NUM_BUFS / 2)
         vrp->num_bufs = virtqueue_get_vring_size(vrp->rvq) * 2;
     else
         vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
 
     vrp->buf_size = MAX_RPMSG_BUF_SIZE;
 
     total_buf_space = vrp->num_bufs * vrp->buf_size;
 
     /* allocate coherent memory for the buffers */
     bufs_va = dma_alloc_coherent(vdev->dev.parent,
                      total_buf_space, &vrp->bufs_dma,
                      GFP_KERNEL);
     if (!bufs_va) {
         err = -ENOMEM;
         goto vqs_del;
     }
 
     dev_dbg(&vdev->dev, "buffers: va %pK, dma %pad\n",
         bufs_va, &vrp->bufs_dma);
 
     /* half of the buffers is dedicated for RX */
     vrp->rbufs = bufs_va;
 
     /* and half is dedicated for TX */
     vrp->sbufs = bufs_va + total_buf_space / 2;
 
     /* set up the receive buffers */
     for (i = 0; i < vrp->num_bufs / 2; i++) {
         struct scatterlist sg;
         void *cpu_addr = vrp->rbufs + i * vrp->buf_size;
 
         rpmsg_sg_init(&sg, cpu_addr, vrp->buf_size);
 
         err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
                       GFP_KERNEL);
         WARN_ON(err); /* sanity check; this can't really happen */
     }
 
     /* suppress "tx-complete" interrupts */
     virtqueue_disable_cb(vrp->svq);
 
     vdev->priv = vrp;
 
     rpdev_ctrl = rpmsg_virtio_add_ctrl_dev(vdev);
     if (IS_ERR(rpdev_ctrl)) {
         err = PTR_ERR(rpdev_ctrl);
         goto free_coherent;
     }
 
     /* if supported by the remote processor, enable the name service */
     if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
         vch = kzalloc(sizeof(*vch), GFP_KERNEL);
         if (!vch) {
             err = -ENOMEM;
             goto free_ctrldev;
         }
 
         /* Link the channel to our vrp */
         vch->vrp = vrp;
 
         /* Assign public information to the rpmsg_device */
         rpdev_ns = &vch->rpdev;
         rpdev_ns->ops = &virtio_rpmsg_ops;
         rpdev_ns->little_endian = virtio_is_little_endian(vrp->vdev);
 
         rpdev_ns->dev.parent = &vrp->vdev->dev;
         rpdev_ns->dev.release = virtio_rpmsg_release_device;
 
         err = rpmsg_ns_register_device(rpdev_ns);
         if (err)
             /* vch will be free in virtio_rpmsg_release_device() */
             goto free_ctrldev;
     }
 
     /*
      * Prepare to kick but don't notify yet - we can't do this before
      * device is ready.
      */
     notify = virtqueue_kick_prepare(vrp->rvq);
 
     /* From this point on, we can notify and get callbacks. */
     virtio_device_ready(vdev);
 
     /* tell the remote processor it can start sending messages */
     /*
      * this might be concurrent with callbacks, but we are only
      * doing notify, not a full kick here, so that's ok.
      */
     if (notify)
         virtqueue_notify(vrp->rvq);
 
     dev_info(&vdev->dev, "rpmsg host is online\n");
 
     return 0;
 
 free_ctrldev:
     rpmsg_virtio_del_ctrl_dev(rpdev_ctrl);
 free_coherent:
     dma_free_coherent(vdev->dev.parent, total_buf_space,
               bufs_va, vrp->bufs_dma);
 vqs_del:
     vdev->config->del_vqs(vrp->vdev);
 free_vrp:
     kfree(vrp);
     return err;
 }
 
 static int rpmsg_remove_device(struct device *dev, void *data)
 {
     device_unregister(dev);
 
     return 0;
 }
 
 static void rpmsg_remove(struct virtio_device *vdev)
 {
     struct virtproc_info *vrp = vdev->priv;
     size_t total_buf_space = vrp->num_bufs * vrp->buf_size;
     int ret;
 
     virtio_reset_device(vdev);
 
     ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
     if (ret)
         dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
 
     idr_destroy(&vrp->endpoints);
 
     vdev->config->del_vqs(vrp->vdev);
 
     dma_free_coherent(vdev->dev.parent, total_buf_space,
               vrp->rbufs, vrp->bufs_dma);
 
     kfree(vrp);
 }
 
 static struct virtio_device_id id_table[] = {
     { VIRTIO_ID_RPMSG, VIRTIO_DEV_ANY_ID },
     { 0 },
 };
 
 static unsigned int features[] = {
     VIRTIO_RPMSG_F_NS,
 };
 
 static struct virtio_driver virtio_ipc_driver = {
     .feature_table  = features,
     .feature_table_size = ARRAY_SIZE(features),
     .driver.name    = KBUILD_MODNAME,
     .driver.owner   = THIS_MODULE,
     .id_table   = id_table,
     .probe      = rpmsg_probe,
     .remove     = rpmsg_remove,
 };
 
 static int __init rpmsg_init(void)
 {
     int ret;
 
     ret = register_virtio_driver(&virtio_ipc_driver);
     if (ret)
         pr_err("failed to register virtio driver: %d\n", ret);
 
     return ret;
 }
 subsys_initcall(rpmsg_init);
 
 static void __exit rpmsg_fini(void)
 {
     unregister_virtio_driver(&virtio_ipc_driver);
 }
 module_exit(rpmsg_fini);
 
 MODULE_DEVICE_TABLE(virtio, id_table);
 MODULE_DESCRIPTION("Virtio-based remote processor messaging bus");
 MODULE_LICENSE("GPL v2");

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