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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

 /*
  * vga_switcheroo.c - Support for laptop with dual GPU using one set of outputs
  *
  * Copyright (c) 2010 Red Hat Inc.
  * Author : Dave Airlie <airlied@redhat.com>
  *
  * Copyright (c) 2015 Lukas Wunner <lukas@wunner.de>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  * and/or sell copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice (including the next
  * paragraph) shall be included in all copies or substantial portions of the
  * Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  * DEALINGS
  * IN THE SOFTWARE.
  *
  */
 
 #define pr_fmt(fmt) "vga_switcheroo: " fmt
 
 #include <linux/apple-gmux.h>
 #include <linux/console.h>
 #include <linux/debugfs.h>
 #include <linux/fb.h>
 #include <linux/fs.h>
 #include <linux/fbcon.h>
 #include <linux/module.h>
 #include <linux/pci.h>
 #include <linux/pm_domain.h>
 #include <linux/pm_runtime.h>
 #include <linux/seq_file.h>
 #include <linux/uaccess.h>
 #include <linux/vgaarb.h>
 #include <linux/vga_switcheroo.h>
 
 /**
  * DOC: Overview
  *
  * vga_switcheroo is the Linux subsystem for laptop hybrid graphics.
  * These come in two flavors:
  *
  * * muxed: Dual GPUs with a multiplexer chip to switch outputs between GPUs.
  * * muxless: Dual GPUs but only one of them is connected to outputs.
  *   The other one is merely used to offload rendering, its results
  *   are copied over PCIe into the framebuffer. On Linux this is
  *   supported with DRI PRIME.
  *
  * Hybrid graphics started to appear in the late Naughties and were initially
  * all muxed. Newer laptops moved to a muxless architecture for cost reasons.
  * A notable exception is the MacBook Pro which continues to use a mux.
  * Muxes come with varying capabilities: Some switch only the panel, others
  * can also switch external displays. Some switch all display pins at once
  * while others can switch just the DDC lines. (To allow EDID probing
  * for the inactive GPU.) Also, muxes are often used to cut power to the
  * discrete GPU while it is not used.
  *
  * DRM drivers register GPUs with vga_switcheroo, these are henceforth called
  * clients. The mux is called the handler. Muxless machines also register a
  * handler to control the power state of the discrete GPU, its ->switchto
  * callback is a no-op for obvious reasons. The discrete GPU is often equipped
  * with an HDA controller for the HDMI/DP audio signal, this will also
  * register as a client so that vga_switcheroo can take care of the correct
  * suspend/resume order when changing the discrete GPU's power state. In total
  * there can thus be up to three clients: Two vga clients (GPUs) and one audio
  * client (on the discrete GPU). The code is mostly prepared to support
  * machines with more than two GPUs should they become available.
  *
  * The GPU to which the outputs are currently switched is called the
  * active client in vga_switcheroo parlance. The GPU not in use is the
  * inactive client. When the inactive client's DRM driver is loaded,
  * it will be unable to probe the panel's EDID and hence depends on
  * VBIOS to provide its display modes. If the VBIOS modes are bogus or
  * if there is no VBIOS at all (which is common on the MacBook Pro),
  * a client may alternatively request that the DDC lines are temporarily
  * switched to it, provided that the handler supports this. Switching
  * only the DDC lines and not the entire output avoids unnecessary
  * flickering.
  */
 
 /**
  * struct vga_switcheroo_client - registered client
  * @pdev: client pci device
  * @fb_info: framebuffer to which console is remapped on switching
  * @pwr_state: current power state if manual power control is used.
  *  For driver power control, call vga_switcheroo_pwr_state().
  * @ops: client callbacks
  * @id: client identifier. Determining the id requires the handler,
  *  so gpus are initially assigned VGA_SWITCHEROO_UNKNOWN_ID
  *  and later given their true id in vga_switcheroo_enable()
  * @active: whether the outputs are currently switched to this client
  * @driver_power_control: whether power state is controlled by the driver's
  *  runtime pm. If true, writing ON and OFF to the vga_switcheroo debugfs
  *  interface is a no-op so as not to interfere with runtime pm
  * @list: client list
  * @vga_dev: pci device, indicate which GPU is bound to current audio client
  *
  * Registered client. A client can be either a GPU or an audio device on a GPU.
  * For audio clients, the @fb_info and @active members are bogus. For GPU
  * clients, the @vga_dev is bogus.
  */
 struct vga_switcheroo_client {
     struct pci_dev *pdev;
     struct fb_info *fb_info;
     enum vga_switcheroo_state pwr_state;
     const struct vga_switcheroo_client_ops *ops;
     enum vga_switcheroo_client_id id;
     bool active;
     bool driver_power_control;
     struct list_head list;
     struct pci_dev *vga_dev;
 };
 
 /*
  * protects access to struct vgasr_priv
  */
 static DEFINE_MUTEX(vgasr_mutex);
 
 /**
  * struct vgasr_priv - vga_switcheroo private data
  * @active: whether vga_switcheroo is enabled.
  *  Prerequisite is the registration of two GPUs and a handler
  * @delayed_switch_active: whether a delayed switch is pending
  * @delayed_client_id: client to which a delayed switch is pending
  * @debugfs_root: directory for vga_switcheroo debugfs interface
  * @registered_clients: number of registered GPUs
  *  (counting only vga clients, not audio clients)
  * @clients: list of registered clients
  * @handler: registered handler
  * @handler_flags: flags of registered handler
  * @mux_hw_lock: protects mux state
  *  (in particular while DDC lines are temporarily switched)
  * @old_ddc_owner: client to which DDC lines will be switched back on unlock
  *
  * vga_switcheroo private data. Currently only one vga_switcheroo instance
  * per system is supported.
  */
 struct vgasr_priv {
     bool active;
     bool delayed_switch_active;
     enum vga_switcheroo_client_id delayed_client_id;
 
     struct dentry *debugfs_root;
 
     int registered_clients;
     struct list_head clients;
 
     const struct vga_switcheroo_handler *handler;
     enum vga_switcheroo_handler_flags_t handler_flags;
     struct mutex mux_hw_lock;
     int old_ddc_owner;
 };
 
 #define ID_BIT_AUDIO        0x100
 #define client_is_audio(c)      ((c)->id & ID_BIT_AUDIO)
 #define client_is_vga(c)        (!client_is_audio(c))
 #define client_id(c)        ((c)->id & ~ID_BIT_AUDIO)
 
 static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv);
 static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv);
 
 /* only one switcheroo per system */
 static struct vgasr_priv vgasr_priv = {
     .clients = LIST_HEAD_INIT(vgasr_priv.clients),
     .mux_hw_lock = __MUTEX_INITIALIZER(vgasr_priv.mux_hw_lock),
 };
 
 static bool vga_switcheroo_ready(void)
 {
     /* we're ready if we get two clients + handler */
     return !vgasr_priv.active &&
            vgasr_priv.registered_clients == 2 && vgasr_priv.handler;
 }
 
 static void vga_switcheroo_enable(void)
 {
     int ret;
     struct vga_switcheroo_client *client;
 
     /* call the handler to init */
     if (vgasr_priv.handler->init)
         vgasr_priv.handler->init();
 
     list_for_each_entry(client, &vgasr_priv.clients, list) {
         if (!client_is_vga(client) ||
              client_id(client) != VGA_SWITCHEROO_UNKNOWN_ID)
             continue;
 
         ret = vgasr_priv.handler->get_client_id(client->pdev);
         if (ret < 0)
             return;
 
         client->id = ret;
     }
 
     list_for_each_entry(client, &vgasr_priv.clients, list) {
         if (!client_is_audio(client) ||
              client_id(client) != VGA_SWITCHEROO_UNKNOWN_ID)
             continue;
 
         ret = vgasr_priv.handler->get_client_id(client->vga_dev);
         if (ret < 0)
             return;
 
         client->id = ret | ID_BIT_AUDIO;
         if (client->ops->gpu_bound)
             client->ops->gpu_bound(client->pdev, ret);
     }
 
     vga_switcheroo_debugfs_init(&vgasr_priv);
     vgasr_priv.active = true;
 }
 
 /**
  * vga_switcheroo_register_handler() - register handler
  * @handler: handler callbacks
  * @handler_flags: handler flags
  *
  * Register handler. Enable vga_switcheroo if two vga clients have already
  * registered.
  *
  * Return: 0 on success, -EINVAL if a handler was already registered.
  */
 int vga_switcheroo_register_handler(
               const struct vga_switcheroo_handler *handler,
               enum vga_switcheroo_handler_flags_t handler_flags)
 {
     mutex_lock(&vgasr_mutex);
     if (vgasr_priv.handler) {
         mutex_unlock(&vgasr_mutex);
         return -EINVAL;
     }
 
     vgasr_priv.handler = handler;
     vgasr_priv.handler_flags = handler_flags;
     if (vga_switcheroo_ready()) {
         pr_info("enabled\n");
         vga_switcheroo_enable();
     }
     mutex_unlock(&vgasr_mutex);
     return 0;
 }
 EXPORT_SYMBOL(vga_switcheroo_register_handler);
 
 /**
  * vga_switcheroo_unregister_handler() - unregister handler
  *
  * Unregister handler. Disable vga_switcheroo.
  */
 void vga_switcheroo_unregister_handler(void)
 {
     mutex_lock(&vgasr_mutex);
     mutex_lock(&vgasr_priv.mux_hw_lock);
     vgasr_priv.handler_flags = 0;
     vgasr_priv.handler = NULL;
     if (vgasr_priv.active) {
         pr_info("disabled\n");
         vga_switcheroo_debugfs_fini(&vgasr_priv);
         vgasr_priv.active = false;
     }
     mutex_unlock(&vgasr_priv.mux_hw_lock);
     mutex_unlock(&vgasr_mutex);
 }
 EXPORT_SYMBOL(vga_switcheroo_unregister_handler);
 
 /**
  * vga_switcheroo_handler_flags() - obtain handler flags
  *
  * Helper for clients to obtain the handler flags bitmask.
  *
  * Return: Handler flags. A value of 0 means that no handler is registered
  * or that the handler has no special capabilities.
  */
 enum vga_switcheroo_handler_flags_t vga_switcheroo_handler_flags(void)
 {
     return vgasr_priv.handler_flags;
 }
 EXPORT_SYMBOL(vga_switcheroo_handler_flags);
 
 static int register_client(struct pci_dev *pdev,
                const struct vga_switcheroo_client_ops *ops,
                enum vga_switcheroo_client_id id,
                struct pci_dev *vga_dev,
                bool active,
                bool driver_power_control)
 {
     struct vga_switcheroo_client *client;
 
     client = kzalloc(sizeof(*client), GFP_KERNEL);
     if (!client)
         return -ENOMEM;
 
     client->pwr_state = VGA_SWITCHEROO_ON;
     client->pdev = pdev;
     client->ops = ops;
     client->id = id;
     client->active = active;
     client->driver_power_control = driver_power_control;
     client->vga_dev = vga_dev;
 
     mutex_lock(&vgasr_mutex);
     list_add_tail(&client->list, &vgasr_priv.clients);
     if (client_is_vga(client))
         vgasr_priv.registered_clients++;
 
     if (vga_switcheroo_ready()) {
         pr_info("enabled\n");
         vga_switcheroo_enable();
     }
     mutex_unlock(&vgasr_mutex);
     return 0;
 }
 
 /**
  * vga_switcheroo_register_client - register vga client
  * @pdev: client pci device
  * @ops: client callbacks
  * @driver_power_control: whether power state is controlled by the driver's
  *  runtime pm
  *
  * Register vga client (GPU). Enable vga_switcheroo if another GPU and a
  * handler have already registered. The power state of the client is assumed
  * to be ON. Beforehand, vga_switcheroo_client_probe_defer() shall be called
  * to ensure that all prerequisites are met.
  *
  * Return: 0 on success, -ENOMEM on memory allocation error.
  */
 int vga_switcheroo_register_client(struct pci_dev *pdev,
                    const struct vga_switcheroo_client_ops *ops,
                    bool driver_power_control)
 {
     return register_client(pdev, ops, VGA_SWITCHEROO_UNKNOWN_ID, NULL,
                    pdev == vga_default_device(),
                    driver_power_control);
 }
 EXPORT_SYMBOL(vga_switcheroo_register_client);
 
 /**
  * vga_switcheroo_register_audio_client - register audio client
  * @pdev: client pci device
  * @ops: client callbacks
  * @vga_dev:  pci device which is bound to current audio client
  *
  * Register audio client (audio device on a GPU). The client is assumed
  * to use runtime PM. Beforehand, vga_switcheroo_client_probe_defer()
  * shall be called to ensure that all prerequisites are met.
  *
  * Return: 0 on success, -ENOMEM on memory allocation error, -EINVAL on getting
  * client id error.
  */
 int vga_switcheroo_register_audio_client(struct pci_dev *pdev,
             const struct vga_switcheroo_client_ops *ops,
             struct pci_dev *vga_dev)
 {
     enum vga_switcheroo_client_id id = VGA_SWITCHEROO_UNKNOWN_ID;
 
     /*
      * if vga_switcheroo has enabled, that mean two GPU clients and also
      * handler are registered. Get audio client id from bound GPU client
      * id directly, otherwise, set it as VGA_SWITCHEROO_UNKNOWN_ID,
      * it will set to correct id in later when vga_switcheroo_enable()
      * is called.
      */
     mutex_lock(&vgasr_mutex);
     if (vgasr_priv.active) {
         id = vgasr_priv.handler->get_client_id(vga_dev);
         if (id < 0) {
             mutex_unlock(&vgasr_mutex);
             return -EINVAL;
         }
         /* notify if GPU has been already bound */
         if (ops->gpu_bound)
             ops->gpu_bound(pdev, id);
     }
     mutex_unlock(&vgasr_mutex);
 
     return register_client(pdev, ops, id | ID_BIT_AUDIO, vga_dev,
                    false, true);
 }
 EXPORT_SYMBOL(vga_switcheroo_register_audio_client);
 
 static struct vga_switcheroo_client *
 find_client_from_pci(struct list_head *head, struct pci_dev *pdev)
 {
     struct vga_switcheroo_client *client;
 
     list_for_each_entry(client, head, list)
         if (client->pdev == pdev)
             return client;
     return NULL;
 }
 
 static struct vga_switcheroo_client *
 find_client_from_id(struct list_head *head,
             enum vga_switcheroo_client_id client_id)
 {
     struct vga_switcheroo_client *client;
 
     list_for_each_entry(client, head, list)
         if (client->id == client_id)
             return client;
     return NULL;
 }
 
 static struct vga_switcheroo_client *
 find_active_client(struct list_head *head)
 {
     struct vga_switcheroo_client *client;
 
     list_for_each_entry(client, head, list)
         if (client->active)
             return client;
     return NULL;
 }
 
 /**
  * vga_switcheroo_client_probe_defer() - whether to defer probing a given client
  * @pdev: client pci device
  *
  * Determine whether any prerequisites are not fulfilled to probe a given
  * client. Drivers shall invoke this early on in their ->probe callback
  * and return %-EPROBE_DEFER if it evaluates to %true. Thou shalt not
  * register the client ere thou hast called this.
  *
  * Return: %true if probing should be deferred, otherwise %false.
  */
 bool vga_switcheroo_client_probe_defer(struct pci_dev *pdev)
 {
     if ((pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY) {
         /*
          * apple-gmux is needed on pre-retina MacBook Pro
          * to probe the panel if pdev is the inactive GPU.
          */
         if (apple_gmux_present() && pdev != vga_default_device() &&
             !vgasr_priv.handler_flags)
             return true;
     }
 
     return false;
 }
 EXPORT_SYMBOL(vga_switcheroo_client_probe_defer);
 
 static enum vga_switcheroo_state
 vga_switcheroo_pwr_state(struct vga_switcheroo_client *client)
 {
     if (client->driver_power_control)
         if (pm_runtime_enabled(&client->pdev->dev) &&
             pm_runtime_active(&client->pdev->dev))
             return VGA_SWITCHEROO_ON;
         else
             return VGA_SWITCHEROO_OFF;
     else
         return client->pwr_state;
 }
 
 /**
  * vga_switcheroo_get_client_state() - obtain power state of a given client
  * @pdev: client pci device
  *
  * Obtain power state of a given client as seen from vga_switcheroo.
  * The function is only called from hda_intel.c.
  *
  * Return: Power state.
  */
 enum vga_switcheroo_state vga_switcheroo_get_client_state(struct pci_dev *pdev)
 {
     struct vga_switcheroo_client *client;
     enum vga_switcheroo_state ret;
 
     mutex_lock(&vgasr_mutex);
     client = find_client_from_pci(&vgasr_priv.clients, pdev);
     if (!client)
         ret = VGA_SWITCHEROO_NOT_FOUND;
     else
         ret = vga_switcheroo_pwr_state(client);
     mutex_unlock(&vgasr_mutex);
     return ret;
 }
 EXPORT_SYMBOL(vga_switcheroo_get_client_state);
 
 /**
  * vga_switcheroo_unregister_client() - unregister client
  * @pdev: client pci device
  *
  * Unregister client. Disable vga_switcheroo if this is a vga client (GPU).
  */
 void vga_switcheroo_unregister_client(struct pci_dev *pdev)
 {
     struct vga_switcheroo_client *client;
 
     mutex_lock(&vgasr_mutex);
     client = find_client_from_pci(&vgasr_priv.clients, pdev);
     if (client) {
         if (client_is_vga(client))
             vgasr_priv.registered_clients--;
         list_del(&client->list);
         kfree(client);
     }
     if (vgasr_priv.active && vgasr_priv.registered_clients < 2) {
         pr_info("disabled\n");
         vga_switcheroo_debugfs_fini(&vgasr_priv);
         vgasr_priv.active = false;
     }
     mutex_unlock(&vgasr_mutex);
 }
 EXPORT_SYMBOL(vga_switcheroo_unregister_client);
 
 /**
  * vga_switcheroo_client_fb_set() - set framebuffer of a given client
  * @pdev: client pci device
  * @info: framebuffer
  *
  * Set framebuffer of a given client. The console will be remapped to this
  * on switching.
  */
 void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
                  struct fb_info *info)
 {
     struct vga_switcheroo_client *client;
 
     mutex_lock(&vgasr_mutex);
     client = find_client_from_pci(&vgasr_priv.clients, pdev);
     if (client)
         client->fb_info = info;
     mutex_unlock(&vgasr_mutex);
 }
 EXPORT_SYMBOL(vga_switcheroo_client_fb_set);
 
 /**
  * vga_switcheroo_lock_ddc() - temporarily switch DDC lines to a given client
  * @pdev: client pci device
  *
  * Temporarily switch DDC lines to the client identified by @pdev
  * (but leave the outputs otherwise switched to where they are).
  * This allows the inactive client to probe EDID. The DDC lines must
  * afterwards be switched back by calling vga_switcheroo_unlock_ddc(),
  * even if this function returns an error.
  *
  * Return: Previous DDC owner on success or a negative int on error.
  * Specifically, %-ENODEV if no handler has registered or if the handler
  * does not support switching the DDC lines. Also, a negative value
  * returned by the handler is propagated back to the caller.
  * The return value has merely an informational purpose for any caller
  * which might be interested in it. It is acceptable to ignore the return
  * value and simply rely on the result of the subsequent EDID probe,
  * which will be %NULL if DDC switching failed.
  */
 int vga_switcheroo_lock_ddc(struct pci_dev *pdev)
 {
     enum vga_switcheroo_client_id id;
 
     mutex_lock(&vgasr_priv.mux_hw_lock);
     if (!vgasr_priv.handler || !vgasr_priv.handler->switch_ddc) {
         vgasr_priv.old_ddc_owner = -ENODEV;
         return -ENODEV;
     }
 
     id = vgasr_priv.handler->get_client_id(pdev);
     vgasr_priv.old_ddc_owner = vgasr_priv.handler->switch_ddc(id);
     return vgasr_priv.old_ddc_owner;
 }
 EXPORT_SYMBOL(vga_switcheroo_lock_ddc);
 
 /**
  * vga_switcheroo_unlock_ddc() - switch DDC lines back to previous owner
  * @pdev: client pci device
  *
  * Switch DDC lines back to the previous owner after calling
  * vga_switcheroo_lock_ddc(). This must be called even if
  * vga_switcheroo_lock_ddc() returned an error.
  *
  * Return: Previous DDC owner on success (i.e. the client identifier of @pdev)
  * or a negative int on error.
  * Specifically, %-ENODEV if no handler has registered or if the handler
  * does not support switching the DDC lines. Also, a negative value
  * returned by the handler is propagated back to the caller.
  * Finally, invoking this function without calling vga_switcheroo_lock_ddc()
  * first is not allowed and will result in %-EINVAL.
  */
 int vga_switcheroo_unlock_ddc(struct pci_dev *pdev)
 {
     enum vga_switcheroo_client_id id;
     int ret = vgasr_priv.old_ddc_owner;
 
     if (WARN_ON_ONCE(!mutex_is_locked(&vgasr_priv.mux_hw_lock)))
         return -EINVAL;
 
     if (vgasr_priv.old_ddc_owner >= 0) {
         id = vgasr_priv.handler->get_client_id(pdev);
         if (vgasr_priv.old_ddc_owner != id)
             ret = vgasr_priv.handler->switch_ddc(
                              vgasr_priv.old_ddc_owner);
     }
     mutex_unlock(&vgasr_priv.mux_hw_lock);
     return ret;
 }
 EXPORT_SYMBOL(vga_switcheroo_unlock_ddc);
 
 /**
  * DOC: Manual switching and manual power control
  *
  * In this mode of use, the file /sys/kernel/debug/vgaswitcheroo/switch
  * can be read to retrieve the current vga_switcheroo state and commands
  * can be written to it to change the state. The file appears as soon as
  * two GPU drivers and one handler have registered with vga_switcheroo.
  * The following commands are understood:
  *
  * * OFF: Power off the device not in use.
  * * ON: Power on the device not in use.
  * * IGD: Switch to the integrated graphics device.
  *   Power on the integrated GPU if necessary, power off the discrete GPU.
  *   Prerequisite is that no user space processes (e.g. Xorg, alsactl)
  *   have opened device files of the GPUs or the audio client. If the
  *   switch fails, the user may invoke lsof(8) or fuser(1) on /dev/dri/
  *   and /dev/snd/controlC1 to identify processes blocking the switch.
  * * DIS: Switch to the discrete graphics device.
  * * DIGD: Delayed switch to the integrated graphics device.
  *   This will perform the switch once the last user space process has
  *   closed the device files of the GPUs and the audio client.
  * * DDIS: Delayed switch to the discrete graphics device.
  * * MIGD: Mux-only switch to the integrated graphics device.
  *   Does not remap console or change the power state of either gpu.
  *   If the integrated GPU is currently off, the screen will turn black.
  *   If it is on, the screen will show whatever happens to be in VRAM.
  *   Either way, the user has to blindly enter the command to switch back.
  * * MDIS: Mux-only switch to the discrete graphics device.
  *
  * For GPUs whose power state is controlled by the driver's runtime pm,
  * the ON and OFF commands are a no-op (see next section).
  *
  * For muxless machines, the IGD/DIS, DIGD/DDIS and MIGD/MDIS commands
  * should not be used.
  */
 
 static int vga_switcheroo_show(struct seq_file *m, void *v)
 {
     struct vga_switcheroo_client *client;
     int i = 0;
 
     mutex_lock(&vgasr_mutex);
     list_for_each_entry(client, &vgasr_priv.clients, list) {
         seq_printf(m, "%d:%s%s:%c:%s%s:%s\n", i,
                client_id(client) == VGA_SWITCHEROO_DIS ? "DIS" :
                                      "IGD",
                client_is_vga(client) ? "" : "-Audio",
                client->active ? '+' : ' ',
                client->driver_power_control ? "Dyn" : "",
                vga_switcheroo_pwr_state(client) ? "Pwr" : "Off",
                pci_name(client->pdev));
         i++;
     }
     mutex_unlock(&vgasr_mutex);
     return 0;
 }
 
 static int vga_switcheroo_debugfs_open(struct inode *inode, struct file *file)
 {
     return single_open(file, vga_switcheroo_show, NULL);
 }
 
 static int vga_switchon(struct vga_switcheroo_client *client)
 {
     if (client->driver_power_control)
         return 0;
     if (vgasr_priv.handler->power_state)
         vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_ON);
     /* call the driver callback to turn on device */
     client->ops->set_gpu_state(client->pdev, VGA_SWITCHEROO_ON);
     client->pwr_state = VGA_SWITCHEROO_ON;
     return 0;
 }
 
 static int vga_switchoff(struct vga_switcheroo_client *client)
 {
     if (client->driver_power_control)
         return 0;
     /* call the driver callback to turn off device */
     client->ops->set_gpu_state(client->pdev, VGA_SWITCHEROO_OFF);
     if (vgasr_priv.handler->power_state)
         vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_OFF);
     client->pwr_state = VGA_SWITCHEROO_OFF;
     return 0;
 }
 
 static void set_audio_state(enum vga_switcheroo_client_id id,
                 enum vga_switcheroo_state state)
 {
     struct vga_switcheroo_client *client;
 
     client = find_client_from_id(&vgasr_priv.clients, id | ID_BIT_AUDIO);
     if (client)
         client->ops->set_gpu_state(client->pdev, state);
 }
 
 /* stage one happens before delay */
 static int vga_switchto_stage1(struct vga_switcheroo_client *new_client)
 {
     struct vga_switcheroo_client *active;
 
     active = find_active_client(&vgasr_priv.clients);
     if (!active)
         return 0;
 
     if (vga_switcheroo_pwr_state(new_client) == VGA_SWITCHEROO_OFF)
         vga_switchon(new_client);
 
     vga_set_default_device(new_client->pdev);
     return 0;
 }
 
 /* post delay */
 static int vga_switchto_stage2(struct vga_switcheroo_client *new_client)
 {
     int ret;
     struct vga_switcheroo_client *active;
 
     active = find_active_client(&vgasr_priv.clients);
     if (!active)
         return 0;
 
     active->active = false;
 
     /* let HDA controller autosuspend if GPU uses driver power control */
     if (!active->driver_power_control)
         set_audio_state(active->id, VGA_SWITCHEROO_OFF);
 
     if (new_client->fb_info)
         fbcon_remap_all(new_client->fb_info);
 
     mutex_lock(&vgasr_priv.mux_hw_lock);
     ret = vgasr_priv.handler->switchto(new_client->id);
     mutex_unlock(&vgasr_priv.mux_hw_lock);
     if (ret)
         return ret;
 
     if (new_client->ops->reprobe)
         new_client->ops->reprobe(new_client->pdev);
 
     if (vga_switcheroo_pwr_state(active) == VGA_SWITCHEROO_ON)
         vga_switchoff(active);
 
     /* let HDA controller autoresume if GPU uses driver power control */
     if (!new_client->driver_power_control)
         set_audio_state(new_client->id, VGA_SWITCHEROO_ON);
 
     new_client->active = true;
     return 0;
 }
 
 static bool check_can_switch(void)
 {
     struct vga_switcheroo_client *client;
 
     list_for_each_entry(client, &vgasr_priv.clients, list) {
         if (!client->ops->can_switch(client->pdev)) {
             pr_err("client %x refused switch\n", client->id);
             return false;
         }
     }
     return true;
 }
 
 static ssize_t
 vga_switcheroo_debugfs_write(struct file *filp, const char __user *ubuf,
                  size_t cnt, loff_t *ppos)
 {
     char usercmd[64];
     int ret;
     bool delay = false, can_switch;
     bool just_mux = false;
     enum vga_switcheroo_client_id client_id = VGA_SWITCHEROO_UNKNOWN_ID;
     struct vga_switcheroo_client *client = NULL;
 
     if (cnt > 63)
         cnt = 63;
 
     if (copy_from_user(usercmd, ubuf, cnt))
         return -EFAULT;
 
     mutex_lock(&vgasr_mutex);
 
     if (!vgasr_priv.active) {
         cnt = -EINVAL;
         goto out;
     }
 
     /* pwr off the device not in use */
     if (strncmp(usercmd, "OFF", 3) == 0) {
         list_for_each_entry(client, &vgasr_priv.clients, list) {
             if (client->active || client_is_audio(client))
                 continue;
             if (client->driver_power_control)
                 continue;
             set_audio_state(client->id, VGA_SWITCHEROO_OFF);
             if (client->pwr_state == VGA_SWITCHEROO_ON)
                 vga_switchoff(client);
         }
         goto out;
     }
     /* pwr on the device not in use */
     if (strncmp(usercmd, "ON", 2) == 0) {
         list_for_each_entry(client, &vgasr_priv.clients, list) {
             if (client->active || client_is_audio(client))
                 continue;
             if (client->driver_power_control)
                 continue;
             if (client->pwr_state == VGA_SWITCHEROO_OFF)
                 vga_switchon(client);
             set_audio_state(client->id, VGA_SWITCHEROO_ON);
         }
         goto out;
     }
 
     /* request a delayed switch - test can we switch now */
     if (strncmp(usercmd, "DIGD", 4) == 0) {
         client_id = VGA_SWITCHEROO_IGD;
         delay = true;
     }
 
     if (strncmp(usercmd, "DDIS", 4) == 0) {
         client_id = VGA_SWITCHEROO_DIS;
         delay = true;
     }
 
     if (strncmp(usercmd, "IGD", 3) == 0)
         client_id = VGA_SWITCHEROO_IGD;
 
     if (strncmp(usercmd, "DIS", 3) == 0)
         client_id = VGA_SWITCHEROO_DIS;
 
     if (strncmp(usercmd, "MIGD", 4) == 0) {
         just_mux = true;
         client_id = VGA_SWITCHEROO_IGD;
     }
     if (strncmp(usercmd, "MDIS", 4) == 0) {
         just_mux = true;
         client_id = VGA_SWITCHEROO_DIS;
     }
 
     if (client_id == VGA_SWITCHEROO_UNKNOWN_ID)
         goto out;
     client = find_client_from_id(&vgasr_priv.clients, client_id);
     if (!client)
         goto out;
 
     vgasr_priv.delayed_switch_active = false;
 
     if (just_mux) {
         mutex_lock(&vgasr_priv.mux_hw_lock);
         ret = vgasr_priv.handler->switchto(client_id);
         mutex_unlock(&vgasr_priv.mux_hw_lock);
         goto out;
     }
 
     if (client->active)
         goto out;
 
     /* okay we want a switch - test if devices are willing to switch */
     can_switch = check_can_switch();
 
     if (can_switch == false && delay == false)
         goto out;
 
     if (can_switch) {
         ret = vga_switchto_stage1(client);
         if (ret)
             pr_err("switching failed stage 1 %d\n", ret);
 
         ret = vga_switchto_stage2(client);
         if (ret)
             pr_err("switching failed stage 2 %d\n", ret);
 
     } else {
         pr_info("setting delayed switch to client %d\n", client->id);
         vgasr_priv.delayed_switch_active = true;
         vgasr_priv.delayed_client_id = client_id;
 
         ret = vga_switchto_stage1(client);
         if (ret)
             pr_err("delayed switching stage 1 failed %d\n", ret);
     }
 
 out:
     mutex_unlock(&vgasr_mutex);
     return cnt;
 }
 
 static const struct file_operations vga_switcheroo_debugfs_fops = {
     .owner = THIS_MODULE,
     .open = vga_switcheroo_debugfs_open,
     .write = vga_switcheroo_debugfs_write,
     .read = seq_read,
     .llseek = seq_lseek,
     .release = single_release,
 };
 
 static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv)
 {
     debugfs_remove_recursive(priv->debugfs_root);
     priv->debugfs_root = NULL;
 }
 
 static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv)
 {
     /* already initialised */
     if (priv->debugfs_root)
         return;
 
     priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL);
 
     debugfs_create_file("switch", 0644, priv->debugfs_root, NULL,
                 &vga_switcheroo_debugfs_fops);
 }
 
 /**
  * vga_switcheroo_process_delayed_switch() - helper for delayed switching
  *
  * Process a delayed switch if one is pending. DRM drivers should call this
  * from their ->lastclose callback.
  *
  * Return: 0 on success. -EINVAL if no delayed switch is pending, if the client
  * has unregistered in the meantime or if there are other clients blocking the
  * switch. If the actual switch fails, an error is reported and 0 is returned.
  */
 int vga_switcheroo_process_delayed_switch(void)
 {
     struct vga_switcheroo_client *client;
     int ret;
     int err = -EINVAL;
 
     mutex_lock(&vgasr_mutex);
     if (!vgasr_priv.delayed_switch_active)
         goto err;
 
     pr_info("processing delayed switch to %d\n",
         vgasr_priv.delayed_client_id);
 
     client = find_client_from_id(&vgasr_priv.clients,
                      vgasr_priv.delayed_client_id);
     if (!client || !check_can_switch())
         goto err;
 
     ret = vga_switchto_stage2(client);
     if (ret)
         pr_err("delayed switching failed stage 2 %d\n", ret);
 
     vgasr_priv.delayed_switch_active = false;
     err = 0;
 err:
     mutex_unlock(&vgasr_mutex);
     return err;
 }
 EXPORT_SYMBOL(vga_switcheroo_process_delayed_switch);
 
 /**
  * DOC: Driver power control
  *
  * In this mode of use, the discrete GPU automatically powers up and down at
  * the discretion of the driver's runtime pm. On muxed machines, the user may
  * still influence the muxer state by way of the debugfs interface, however
  * the ON and OFF commands become a no-op for the discrete GPU.
  *
  * This mode is the default on Nvidia HybridPower/Optimus and ATI PowerXpress.
  * Specifying nouveau.runpm=0, radeon.runpm=0 or amdgpu.runpm=0 on the kernel
  * command line disables it.
  *
  * After the GPU has been suspended, the handler needs to be called to cut
  * power to the GPU. Likewise it needs to reinstate power before the GPU
  * can resume. This is achieved by vga_switcheroo_init_domain_pm_ops(),
  * which augments the GPU's suspend/resume functions by the requisite
  * calls to the handler.
  *
  * When the audio device resumes, the GPU needs to be woken. This is achieved
  * by a PCI quirk which calls device_link_add() to declare a dependency on the
  * GPU. That way, the GPU is kept awake whenever and as long as the audio
  * device is in use.
  *
  * On muxed machines, if the mux is initially switched to the discrete GPU,
  * the user ends up with a black screen when the GPU powers down after boot.
  * As a workaround, the mux is forced to the integrated GPU on runtime suspend,
  * cf. https://bugs.freedesktop.org/show_bug.cgi?id=75917
  */
 
 static void vga_switcheroo_power_switch(struct pci_dev *pdev,
                     enum vga_switcheroo_state state)
 {
     struct vga_switcheroo_client *client;
 
     if (!vgasr_priv.handler->power_state)
         return;
 
     client = find_client_from_pci(&vgasr_priv.clients, pdev);
     if (!client)
         return;
 
     if (!client->driver_power_control)
         return;
 
     vgasr_priv.handler->power_state(client->id, state);
 }
 
 /* switcheroo power domain */
 static int vga_switcheroo_runtime_suspend(struct device *dev)
 {
     struct pci_dev *pdev = to_pci_dev(dev);
     int ret;
 
     ret = dev->bus->pm->runtime_suspend(dev);
     if (ret)
         return ret;
     mutex_lock(&vgasr_mutex);
     if (vgasr_priv.handler->switchto) {
         mutex_lock(&vgasr_priv.mux_hw_lock);
         vgasr_priv.handler->switchto(VGA_SWITCHEROO_IGD);
         mutex_unlock(&vgasr_priv.mux_hw_lock);
     }
     pci_bus_set_current_state(pdev->bus, PCI_D3cold);
     vga_switcheroo_power_switch(pdev, VGA_SWITCHEROO_OFF);
     mutex_unlock(&vgasr_mutex);
     return 0;
 }
 
 static int vga_switcheroo_runtime_resume(struct device *dev)
 {
     struct pci_dev *pdev = to_pci_dev(dev);
 
     mutex_lock(&vgasr_mutex);
     vga_switcheroo_power_switch(pdev, VGA_SWITCHEROO_ON);
     mutex_unlock(&vgasr_mutex);
     pci_resume_bus(pdev->bus);
     return dev->bus->pm->runtime_resume(dev);
 }
 
 /**
  * vga_switcheroo_init_domain_pm_ops() - helper for driver power control
  * @dev: vga client device
  * @domain: power domain
  *
  * Helper for GPUs whose power state is controlled by the driver's runtime pm.
  * After the GPU has been suspended, the handler needs to be called to cut
  * power to the GPU. Likewise it needs to reinstate power before the GPU
  * can resume. To this end, this helper augments the suspend/resume functions
  * by the requisite calls to the handler. It needs only be called on platforms
  * where the power switch is separate to the device being powered down.
  */
 int vga_switcheroo_init_domain_pm_ops(struct device *dev,
                       struct dev_pm_domain *domain)
 {
     /* copy over all the bus versions */
     if (dev->bus && dev->bus->pm) {
         domain->ops = *dev->bus->pm;
         domain->ops.runtime_suspend = vga_switcheroo_runtime_suspend;
         domain->ops.runtime_resume = vga_switcheroo_runtime_resume;
 
         dev_pm_domain_set(dev, domain);
         return 0;
     }
     dev_pm_domain_set(dev, NULL);
     return -EINVAL;
 }
 EXPORT_SYMBOL(vga_switcheroo_init_domain_pm_ops);
 
 void vga_switcheroo_fini_domain_pm_ops(struct device *dev)
 {
     dev_pm_domain_set(dev, NULL);
 }
 EXPORT_SYMBOL(vga_switcheroo_fini_domain_pm_ops);

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