OSCL-LXR linux-6.0.1/​drivers/​gpu/​drm/​drm_drv.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

 /*
  * Created: Fri Jan 19 10:48:35 2001 by faith@acm.org
  *
  * Copyright 2001 VA Linux Systems, Inc., Sunnyvale, California.
  * All Rights Reserved.
  *
  * Author Rickard E. (Rik) Faith <faith@valinux.com>
  *
  * 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
  * PRECISION INSIGHT AND/OR ITS SUPPLIERS 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.
  */
 
 #include <linux/debugfs.h>
 #include <linux/fs.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/mount.h>
 #include <linux/pseudo_fs.h>
 #include <linux/slab.h>
 #include <linux/srcu.h>
 
 #include <drm/drm_cache.h>
 #include <drm/drm_client.h>
 #include <drm/drm_color_mgmt.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
 #include <drm/drm_managed.h>
 #include <drm/drm_mode_object.h>
 #include <drm/drm_print.h>
 #include <drm/drm_privacy_screen_machine.h>
 
 #include "drm_crtc_internal.h"
 #include "drm_internal.h"
 #include "drm_legacy.h"
 
 MODULE_AUTHOR("Gareth Hughes, Leif Delgass, José Fonseca, Jon Smirl");
 MODULE_DESCRIPTION("DRM shared core routines");
 MODULE_LICENSE("GPL and additional rights");
 
 static DEFINE_SPINLOCK(drm_minor_lock);
 static struct idr drm_minors_idr;
 
 /*
  * If the drm core fails to init for whatever reason,
  * we should prevent any drivers from registering with it.
  * It's best to check this at drm_dev_init(), as some drivers
  * prefer to embed struct drm_device into their own device
  * structure and call drm_dev_init() themselves.
  */
 static bool drm_core_init_complete;
 
 static struct dentry *drm_debugfs_root;
 
 DEFINE_STATIC_SRCU(drm_unplug_srcu);
 
 /*
  * DRM Minors
  * A DRM device can provide several char-dev interfaces on the DRM-Major. Each
  * of them is represented by a drm_minor object. Depending on the capabilities
  * of the device-driver, different interfaces are registered.
  *
  * Minors can be accessed via dev->$minor_name. This pointer is either
  * NULL or a valid drm_minor pointer and stays valid as long as the device is
  * valid. This means, DRM minors have the same life-time as the underlying
  * device. However, this doesn't mean that the minor is active. Minors are
  * registered and unregistered dynamically according to device-state.
  */
 
 static struct drm_minor **drm_minor_get_slot(struct drm_device *dev,
                          unsigned int type)
 {
     switch (type) {
     case DRM_MINOR_PRIMARY:
         return &dev->primary;
     case DRM_MINOR_RENDER:
         return &dev->render;
     default:
         BUG();
     }
 }
 
 static void drm_minor_alloc_release(struct drm_device *dev, void *data)
 {
     struct drm_minor *minor = data;
     unsigned long flags;
 
     WARN_ON(dev != minor->dev);
 
     put_device(minor->kdev);
 
     spin_lock_irqsave(&drm_minor_lock, flags);
     idr_remove(&drm_minors_idr, minor->index);
     spin_unlock_irqrestore(&drm_minor_lock, flags);
 }
 
 static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 {
     struct drm_minor *minor;
     unsigned long flags;
     int r;
 
     minor = drmm_kzalloc(dev, sizeof(*minor), GFP_KERNEL);
     if (!minor)
         return -ENOMEM;
 
     minor->type = type;
     minor->dev = dev;
 
     idr_preload(GFP_KERNEL);
     spin_lock_irqsave(&drm_minor_lock, flags);
     r = idr_alloc(&drm_minors_idr,
               NULL,
               64 * type,
               64 * (type + 1),
               GFP_NOWAIT);
     spin_unlock_irqrestore(&drm_minor_lock, flags);
     idr_preload_end();
 
     if (r < 0)
         return r;
 
     minor->index = r;
 
     r = drmm_add_action_or_reset(dev, drm_minor_alloc_release, minor);
     if (r)
         return r;
 
     minor->kdev = drm_sysfs_minor_alloc(minor);
     if (IS_ERR(minor->kdev))
         return PTR_ERR(minor->kdev);
 
     *drm_minor_get_slot(dev, type) = minor;
     return 0;
 }
 
 static int drm_minor_register(struct drm_device *dev, unsigned int type)
 {
     struct drm_minor *minor;
     unsigned long flags;
     int ret;
 
     DRM_DEBUG("\n");
 
     minor = *drm_minor_get_slot(dev, type);
     if (!minor)
         return 0;
 
     ret = drm_debugfs_init(minor, minor->index, drm_debugfs_root);
     if (ret) {
         DRM_ERROR("DRM: Failed to initialize /sys/kernel/debug/dri.\n");
         goto err_debugfs;
     }
 
     ret = device_add(minor->kdev);
     if (ret)
         goto err_debugfs;
 
     /* replace NULL with @minor so lookups will succeed from now on */
     spin_lock_irqsave(&drm_minor_lock, flags);
     idr_replace(&drm_minors_idr, minor, minor->index);
     spin_unlock_irqrestore(&drm_minor_lock, flags);
 
     DRM_DEBUG("new minor registered %d\n", minor->index);
     return 0;
 
 err_debugfs:
     drm_debugfs_cleanup(minor);
     return ret;
 }
 
 static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
 {
     struct drm_minor *minor;
     unsigned long flags;
 
     minor = *drm_minor_get_slot(dev, type);
     if (!minor || !device_is_registered(minor->kdev))
         return;
 
     /* replace @minor with NULL so lookups will fail from now on */
     spin_lock_irqsave(&drm_minor_lock, flags);
     idr_replace(&drm_minors_idr, NULL, minor->index);
     spin_unlock_irqrestore(&drm_minor_lock, flags);
 
     device_del(minor->kdev);
     dev_set_drvdata(minor->kdev, NULL); /* safety belt */
     drm_debugfs_cleanup(minor);
 }
 
 /*
  * Looks up the given minor-ID and returns the respective DRM-minor object. The
  * refence-count of the underlying device is increased so you must release this
  * object with drm_minor_release().
  *
  * As long as you hold this minor, it is guaranteed that the object and the
  * minor->dev pointer will stay valid! However, the device may get unplugged and
  * unregistered while you hold the minor.
  */
 struct drm_minor *drm_minor_acquire(unsigned int minor_id)
 {
     struct drm_minor *minor;
     unsigned long flags;
 
     spin_lock_irqsave(&drm_minor_lock, flags);
     minor = idr_find(&drm_minors_idr, minor_id);
     if (minor)
         drm_dev_get(minor->dev);
     spin_unlock_irqrestore(&drm_minor_lock, flags);
 
     if (!minor) {
         return ERR_PTR(-ENODEV);
     } else if (drm_dev_is_unplugged(minor->dev)) {
         drm_dev_put(minor->dev);
         return ERR_PTR(-ENODEV);
     }
 
     return minor;
 }
 
 void drm_minor_release(struct drm_minor *minor)
 {
     drm_dev_put(minor->dev);
 }
 
 /**
  * DOC: driver instance overview
  *
  * A device instance for a drm driver is represented by &struct drm_device. This
  * is allocated and initialized with devm_drm_dev_alloc(), usually from
  * bus-specific ->probe() callbacks implemented by the driver. The driver then
  * needs to initialize all the various subsystems for the drm device like memory
  * management, vblank handling, modesetting support and initial output
  * configuration plus obviously initialize all the corresponding hardware bits.
  * Finally when everything is up and running and ready for userspace the device
  * instance can be published using drm_dev_register().
  *
  * There is also deprecated support for initializing device instances using
  * bus-specific helpers and the &drm_driver.load callback. But due to
  * backwards-compatibility needs the device instance have to be published too
  * early, which requires unpretty global locking to make safe and is therefore
  * only support for existing drivers not yet converted to the new scheme.
  *
  * When cleaning up a device instance everything needs to be done in reverse:
  * First unpublish the device instance with drm_dev_unregister(). Then clean up
  * any other resources allocated at device initialization and drop the driver's
  * reference to &drm_device using drm_dev_put().
  *
  * Note that any allocation or resource which is visible to userspace must be
  * released only when the final drm_dev_put() is called, and not when the
  * driver is unbound from the underlying physical struct &device. Best to use
  * &drm_device managed resources with drmm_add_action(), drmm_kmalloc() and
  * related functions.
  *
  * devres managed resources like devm_kmalloc() can only be used for resources
  * directly related to the underlying hardware device, and only used in code
  * paths fully protected by drm_dev_enter() and drm_dev_exit().
  *
  * Display driver example
  * ~~~~~~~~~~~~~~~~~~~~~~
  *
  * The following example shows a typical structure of a DRM display driver.
  * The example focus on the probe() function and the other functions that is
  * almost always present and serves as a demonstration of devm_drm_dev_alloc().
  *
  * .. code-block:: c
  *
  *  struct driver_device {
  *      struct drm_device drm;
  *      void *userspace_facing;
  *      struct clk *pclk;
  *  };
  *
  *  static const struct drm_driver driver_drm_driver = {
  *      [...]
  *  };
  *
  *  static int driver_probe(struct platform_device *pdev)
  *  {
  *      struct driver_device *priv;
  *      struct drm_device *drm;
  *      int ret;
  *
  *      priv = devm_drm_dev_alloc(&pdev->dev, &driver_drm_driver,
  *                    struct driver_device, drm);
  *      if (IS_ERR(priv))
  *          return PTR_ERR(priv);
  *      drm = &priv->drm;
  *
  *      ret = drmm_mode_config_init(drm);
  *      if (ret)
  *          return ret;
  *
  *      priv->userspace_facing = drmm_kzalloc(..., GFP_KERNEL);
  *      if (!priv->userspace_facing)
  *          return -ENOMEM;
  *
  *      priv->pclk = devm_clk_get(dev, "PCLK");
  *      if (IS_ERR(priv->pclk))
  *          return PTR_ERR(priv->pclk);
  *
  *      // Further setup, display pipeline etc
  *
  *      platform_set_drvdata(pdev, drm);
  *
  *      drm_mode_config_reset(drm);
  *
  *      ret = drm_dev_register(drm);
  *      if (ret)
  *          return ret;
  *
  *      drm_fbdev_generic_setup(drm, 32);
  *
  *      return 0;
  *  }
  *
  *  // This function is called before the devm_ resources are released
  *  static int driver_remove(struct platform_device *pdev)
  *  {
  *      struct drm_device *drm = platform_get_drvdata(pdev);
  *
  *      drm_dev_unregister(drm);
  *      drm_atomic_helper_shutdown(drm)
  *
  *      return 0;
  *  }
  *
  *  // This function is called on kernel restart and shutdown
  *  static void driver_shutdown(struct platform_device *pdev)
  *  {
  *      drm_atomic_helper_shutdown(platform_get_drvdata(pdev));
  *  }
  *
  *  static int __maybe_unused driver_pm_suspend(struct device *dev)
  *  {
  *      return drm_mode_config_helper_suspend(dev_get_drvdata(dev));
  *  }
  *
  *  static int __maybe_unused driver_pm_resume(struct device *dev)
  *  {
  *      drm_mode_config_helper_resume(dev_get_drvdata(dev));
  *
  *      return 0;
  *  }
  *
  *  static const struct dev_pm_ops driver_pm_ops = {
  *      SET_SYSTEM_SLEEP_PM_OPS(driver_pm_suspend, driver_pm_resume)
  *  };
  *
  *  static struct platform_driver driver_driver = {
  *      .driver = {
  *          [...]
  *          .pm = &driver_pm_ops,
  *      },
  *      .probe = driver_probe,
  *      .remove = driver_remove,
  *      .shutdown = driver_shutdown,
  *  };
  *  module_platform_driver(driver_driver);
  *
  * Drivers that want to support device unplugging (USB, DT overlay unload) should
  * use drm_dev_unplug() instead of drm_dev_unregister(). The driver must protect
  * regions that is accessing device resources to prevent use after they're
  * released. This is done using drm_dev_enter() and drm_dev_exit(). There is one
  * shortcoming however, drm_dev_unplug() marks the drm_device as unplugged before
  * drm_atomic_helper_shutdown() is called. This means that if the disable code
  * paths are protected, they will not run on regular driver module unload,
  * possibly leaving the hardware enabled.
  */
 
 /**
  * drm_put_dev - Unregister and release a DRM device
  * @dev: DRM device
  *
  * Called at module unload time or when a PCI device is unplugged.
  *
  * Cleans up all DRM device, calling drm_lastclose().
  *
  * Note: Use of this function is deprecated. It will eventually go away
  * completely.  Please use drm_dev_unregister() and drm_dev_put() explicitly
  * instead to make sure that the device isn't userspace accessible any more
  * while teardown is in progress, ensuring that userspace can't access an
  * inconsistent state.
  */
 void drm_put_dev(struct drm_device *dev)
 {
     DRM_DEBUG("\n");
 
     if (!dev) {
         DRM_ERROR("cleanup called no dev\n");
         return;
     }
 
     drm_dev_unregister(dev);
     drm_dev_put(dev);
 }
 EXPORT_SYMBOL(drm_put_dev);
 
 /**
  * drm_dev_enter - Enter device critical section
  * @dev: DRM device
  * @idx: Pointer to index that will be passed to the matching drm_dev_exit()
  *
  * This function marks and protects the beginning of a section that should not
  * be entered after the device has been unplugged. The section end is marked
  * with drm_dev_exit(). Calls to this function can be nested.
  *
  * Returns:
  * True if it is OK to enter the section, false otherwise.
  */
 bool drm_dev_enter(struct drm_device *dev, int *idx)
 {
     *idx = srcu_read_lock(&drm_unplug_srcu);
 
     if (dev->unplugged) {
         srcu_read_unlock(&drm_unplug_srcu, *idx);
         return false;
     }
 
     return true;
 }
 EXPORT_SYMBOL(drm_dev_enter);
 
 /**
  * drm_dev_exit - Exit device critical section
  * @idx: index returned from drm_dev_enter()
  *
  * This function marks the end of a section that should not be entered after
  * the device has been unplugged.
  */
 void drm_dev_exit(int idx)
 {
     srcu_read_unlock(&drm_unplug_srcu, idx);
 }
 EXPORT_SYMBOL(drm_dev_exit);
 
 /**
  * drm_dev_unplug - unplug a DRM device
  * @dev: DRM device
  *
  * This unplugs a hotpluggable DRM device, which makes it inaccessible to
  * userspace operations. Entry-points can use drm_dev_enter() and
  * drm_dev_exit() to protect device resources in a race free manner. This
  * essentially unregisters the device like drm_dev_unregister(), but can be
  * called while there are still open users of @dev.
  */
 void drm_dev_unplug(struct drm_device *dev)
 {
     /*
      * After synchronizing any critical read section is guaranteed to see
      * the new value of ->unplugged, and any critical section which might
      * still have seen the old value of ->unplugged is guaranteed to have
      * finished.
      */
     dev->unplugged = true;
     synchronize_srcu(&drm_unplug_srcu);
 
     drm_dev_unregister(dev);
 
     /* Clear all CPU mappings pointing to this device */
     unmap_mapping_range(dev->anon_inode->i_mapping, 0, 0, 1);
 }
 EXPORT_SYMBOL(drm_dev_unplug);
 
 /*
  * DRM internal mount
  * We want to be able to allocate our own "struct address_space" to control
  * memory-mappings in VRAM (or stolen RAM, ...). However, core MM does not allow
  * stand-alone address_space objects, so we need an underlying inode. As there
  * is no way to allocate an independent inode easily, we need a fake internal
  * VFS mount-point.
  *
  * The drm_fs_inode_new() function allocates a new inode, drm_fs_inode_free()
  * frees it again. You are allowed to use iget() and iput() to get references to
  * the inode. But each drm_fs_inode_new() call must be paired with exactly one
  * drm_fs_inode_free() call (which does not have to be the last iput()).
  * We use drm_fs_inode_*() to manage our internal VFS mount-point and share it
  * between multiple inode-users. You could, technically, call
  * iget() + drm_fs_inode_free() directly after alloc and sometime later do an
  * iput(), but this way you'd end up with a new vfsmount for each inode.
  */
 
 static int drm_fs_cnt;
 static struct vfsmount *drm_fs_mnt;
 
 static int drm_fs_init_fs_context(struct fs_context *fc)
 {
     return init_pseudo(fc, 0x010203ff) ? 0 : -ENOMEM;
 }
 
 static struct file_system_type drm_fs_type = {
     .name       = "drm",
     .owner      = THIS_MODULE,
     .init_fs_context = drm_fs_init_fs_context,
     .kill_sb    = kill_anon_super,
 };
 
 static struct inode *drm_fs_inode_new(void)
 {
     struct inode *inode;
     int r;
 
     r = simple_pin_fs(&drm_fs_type, &drm_fs_mnt, &drm_fs_cnt);
     if (r < 0) {
         DRM_ERROR("Cannot mount pseudo fs: %d\n", r);
         return ERR_PTR(r);
     }
 
     inode = alloc_anon_inode(drm_fs_mnt->mnt_sb);
     if (IS_ERR(inode))
         simple_release_fs(&drm_fs_mnt, &drm_fs_cnt);
 
     return inode;
 }
 
 static void drm_fs_inode_free(struct inode *inode)
 {
     if (inode) {
         iput(inode);
         simple_release_fs(&drm_fs_mnt, &drm_fs_cnt);
     }
 }
 
 /**
  * DOC: component helper usage recommendations
  *
  * DRM drivers that drive hardware where a logical device consists of a pile of
  * independent hardware blocks are recommended to use the :ref:`component helper
  * library<component>`. For consistency and better options for code reuse the
  * following guidelines apply:
  *
  *  - The entire device initialization procedure should be run from the
  *    &component_master_ops.master_bind callback, starting with
  *    devm_drm_dev_alloc(), then binding all components with
  *    component_bind_all() and finishing with drm_dev_register().
  *
  *  - The opaque pointer passed to all components through component_bind_all()
  *    should point at &struct drm_device of the device instance, not some driver
  *    specific private structure.
  *
  *  - The component helper fills the niche where further standardization of
  *    interfaces is not practical. When there already is, or will be, a
  *    standardized interface like &drm_bridge or &drm_panel, providing its own
  *    functions to find such components at driver load time, like
  *    drm_of_find_panel_or_bridge(), then the component helper should not be
  *    used.
  */
 
 static void drm_dev_init_release(struct drm_device *dev, void *res)
 {
     drm_legacy_ctxbitmap_cleanup(dev);
     drm_legacy_remove_map_hash(dev);
     drm_fs_inode_free(dev->anon_inode);
 
     put_device(dev->dev);
     /* Prevent use-after-free in drm_managed_release when debugging is
      * enabled. Slightly awkward, but can't really be helped. */
     dev->dev = NULL;
     mutex_destroy(&dev->master_mutex);
     mutex_destroy(&dev->clientlist_mutex);
     mutex_destroy(&dev->filelist_mutex);
     mutex_destroy(&dev->struct_mutex);
     drm_legacy_destroy_members(dev);
 }
 
 static int drm_dev_init(struct drm_device *dev,
             const struct drm_driver *driver,
             struct device *parent)
 {
     struct inode *inode;
     int ret;
 
     if (!drm_core_init_complete) {
         DRM_ERROR("DRM core is not initialized\n");
         return -ENODEV;
     }
 
     if (WARN_ON(!parent))
         return -EINVAL;
 
     kref_init(&dev->ref);
     dev->dev = get_device(parent);
     dev->driver = driver;
 
     INIT_LIST_HEAD(&dev->managed.resources);
     spin_lock_init(&dev->managed.lock);
 
     /* no per-device feature limits by default */
     dev->driver_features = ~0u;
 
     drm_legacy_init_members(dev);
     INIT_LIST_HEAD(&dev->filelist);
     INIT_LIST_HEAD(&dev->filelist_internal);
     INIT_LIST_HEAD(&dev->clientlist);
     INIT_LIST_HEAD(&dev->vblank_event_list);
 
     spin_lock_init(&dev->event_lock);
     mutex_init(&dev->struct_mutex);
     mutex_init(&dev->filelist_mutex);
     mutex_init(&dev->clientlist_mutex);
     mutex_init(&dev->master_mutex);
 
     ret = drmm_add_action(dev, drm_dev_init_release, NULL);
     if (ret)
         return ret;
 
     inode = drm_fs_inode_new();
     if (IS_ERR(inode)) {
         ret = PTR_ERR(inode);
         DRM_ERROR("Cannot allocate anonymous inode: %d\n", ret);
         goto err;
     }
 
     dev->anon_inode = inode;
 
     if (drm_core_check_feature(dev, DRIVER_RENDER)) {
         ret = drm_minor_alloc(dev, DRM_MINOR_RENDER);
         if (ret)
             goto err;
     }
 
     ret = drm_minor_alloc(dev, DRM_MINOR_PRIMARY);
     if (ret)
         goto err;
 
     ret = drm_legacy_create_map_hash(dev);
     if (ret)
         goto err;
 
     drm_legacy_ctxbitmap_init(dev);
 
     if (drm_core_check_feature(dev, DRIVER_GEM)) {
         ret = drm_gem_init(dev);
         if (ret) {
             DRM_ERROR("Cannot initialize graphics execution manager (GEM)\n");
             goto err;
         }
     }
 
     ret = drm_dev_set_unique(dev, dev_name(parent));
     if (ret)
         goto err;
 
     return 0;
 
 err:
     drm_managed_release(dev);
 
     return ret;
 }
 
 static void devm_drm_dev_init_release(void *data)
 {
     drm_dev_put(data);
 }
 
 static int devm_drm_dev_init(struct device *parent,
                  struct drm_device *dev,
                  const struct drm_driver *driver)
 {
     int ret;
 
     ret = drm_dev_init(dev, driver, parent);
     if (ret)
         return ret;
 
     return devm_add_action_or_reset(parent,
                     devm_drm_dev_init_release, dev);
 }
 
 void *__devm_drm_dev_alloc(struct device *parent,
                const struct drm_driver *driver,
                size_t size, size_t offset)
 {
     void *container;
     struct drm_device *drm;
     int ret;
 
     container = kzalloc(size, GFP_KERNEL);
     if (!container)
         return ERR_PTR(-ENOMEM);
 
     drm = container + offset;
     ret = devm_drm_dev_init(parent, drm, driver);
     if (ret) {
         kfree(container);
         return ERR_PTR(ret);
     }
     drmm_add_final_kfree(drm, container);
 
     return container;
 }
 EXPORT_SYMBOL(__devm_drm_dev_alloc);
 
 /**
  * drm_dev_alloc - Allocate new DRM device
  * @driver: DRM driver to allocate device for
  * @parent: Parent device object
  *
  * This is the deprecated version of devm_drm_dev_alloc(), which does not support
  * subclassing through embedding the struct &drm_device in a driver private
  * structure, and which does not support automatic cleanup through devres.
  *
  * RETURNS:
  * Pointer to new DRM device, or ERR_PTR on failure.
  */
 struct drm_device *drm_dev_alloc(const struct drm_driver *driver,
                  struct device *parent)
 {
     struct drm_device *dev;
     int ret;
 
     dev = kzalloc(sizeof(*dev), GFP_KERNEL);
     if (!dev)
         return ERR_PTR(-ENOMEM);
 
     ret = drm_dev_init(dev, driver, parent);
     if (ret) {
         kfree(dev);
         return ERR_PTR(ret);
     }
 
     drmm_add_final_kfree(dev, dev);
 
     return dev;
 }
 EXPORT_SYMBOL(drm_dev_alloc);
 
 static void drm_dev_release(struct kref *ref)
 {
     struct drm_device *dev = container_of(ref, struct drm_device, ref);
 
     if (dev->driver->release)
         dev->driver->release(dev);
 
     drm_managed_release(dev);
 
     kfree(dev->managed.final_kfree);
 }
 
 /**
  * drm_dev_get - Take reference of a DRM device
  * @dev: device to take reference of or NULL
  *
  * This increases the ref-count of @dev by one. You *must* already own a
  * reference when calling this. Use drm_dev_put() to drop this reference
  * again.
  *
  * This function never fails. However, this function does not provide *any*
  * guarantee whether the device is alive or running. It only provides a
  * reference to the object and the memory associated with it.
  */
 void drm_dev_get(struct drm_device *dev)
 {
     if (dev)
         kref_get(&dev->ref);
 }
 EXPORT_SYMBOL(drm_dev_get);
 
 /**
  * drm_dev_put - Drop reference of a DRM device
  * @dev: device to drop reference of or NULL
  *
  * This decreases the ref-count of @dev by one. The device is destroyed if the
  * ref-count drops to zero.
  */
 void drm_dev_put(struct drm_device *dev)
 {
     if (dev)
         kref_put(&dev->ref, drm_dev_release);
 }
 EXPORT_SYMBOL(drm_dev_put);
 
 static int create_compat_control_link(struct drm_device *dev)
 {
     struct drm_minor *minor;
     char *name;
     int ret;
 
     if (!drm_core_check_feature(dev, DRIVER_MODESET))
         return 0;
 
     minor = *drm_minor_get_slot(dev, DRM_MINOR_PRIMARY);
     if (!minor)
         return 0;
 
     /*
      * Some existing userspace out there uses the existing of the controlD*
      * sysfs files to figure out whether it's a modeset driver. It only does
      * readdir, hence a symlink is sufficient (and the least confusing
      * option). Otherwise controlD* is entirely unused.
      *
      * Old controlD chardev have been allocated in the range
      * 64-127.
      */
     name = kasprintf(GFP_KERNEL, "controlD%d", minor->index + 64);
     if (!name)
         return -ENOMEM;
 
     ret = sysfs_create_link(minor->kdev->kobj.parent,
                 &minor->kdev->kobj,
                 name);
 
     kfree(name);
 
     return ret;
 }
 
 static void remove_compat_control_link(struct drm_device *dev)
 {
     struct drm_minor *minor;
     char *name;
 
     if (!drm_core_check_feature(dev, DRIVER_MODESET))
         return;
 
     minor = *drm_minor_get_slot(dev, DRM_MINOR_PRIMARY);
     if (!minor)
         return;
 
     name = kasprintf(GFP_KERNEL, "controlD%d", minor->index + 64);
     if (!name)
         return;
 
     sysfs_remove_link(minor->kdev->kobj.parent, name);
 
     kfree(name);
 }
 
 /**
  * drm_dev_register - Register DRM device
  * @dev: Device to register
  * @flags: Flags passed to the driver's .load() function
  *
  * Register the DRM device @dev with the system, advertise device to user-space
  * and start normal device operation. @dev must be initialized via drm_dev_init()
  * previously.
  *
  * Never call this twice on any device!
  *
  * NOTE: To ensure backward compatibility with existing drivers method this
  * function calls the &drm_driver.load method after registering the device
  * nodes, creating race conditions. Usage of the &drm_driver.load methods is
  * therefore deprecated, drivers must perform all initialization before calling
  * drm_dev_register().
  *
  * RETURNS:
  * 0 on success, negative error code on failure.
  */
 int drm_dev_register(struct drm_device *dev, unsigned long flags)
 {
     const struct drm_driver *driver = dev->driver;
     int ret;
 
     if (!driver->load)
         drm_mode_config_validate(dev);
 
     WARN_ON(!dev->managed.final_kfree);
 
     if (drm_dev_needs_global_mutex(dev))
         mutex_lock(&drm_global_mutex);
 
     ret = drm_minor_register(dev, DRM_MINOR_RENDER);
     if (ret)
         goto err_minors;
 
     ret = drm_minor_register(dev, DRM_MINOR_PRIMARY);
     if (ret)
         goto err_minors;
 
     ret = create_compat_control_link(dev);
     if (ret)
         goto err_minors;
 
     dev->registered = true;
 
     if (dev->driver->load) {
         ret = dev->driver->load(dev, flags);
         if (ret)
             goto err_minors;
     }
 
     if (drm_core_check_feature(dev, DRIVER_MODESET))
         drm_modeset_register_all(dev);
 
     DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
          driver->name, driver->major, driver->minor,
          driver->patchlevel, driver->date,
          dev->dev ? dev_name(dev->dev) : "virtual device",
          dev->primary->index);
 
     goto out_unlock;
 
 err_minors:
     remove_compat_control_link(dev);
     drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
     drm_minor_unregister(dev, DRM_MINOR_RENDER);
 out_unlock:
     if (drm_dev_needs_global_mutex(dev))
         mutex_unlock(&drm_global_mutex);
     return ret;
 }
 EXPORT_SYMBOL(drm_dev_register);
 
 /**
  * drm_dev_unregister - Unregister DRM device
  * @dev: Device to unregister
  *
  * Unregister the DRM device from the system. This does the reverse of
  * drm_dev_register() but does not deallocate the device. The caller must call
  * drm_dev_put() to drop their final reference.
  *
  * A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
  * which can be called while there are still open users of @dev.
  *
  * This should be called first in the device teardown code to make sure
  * userspace can't access the device instance any more.
  */
 void drm_dev_unregister(struct drm_device *dev)
 {
     if (drm_core_check_feature(dev, DRIVER_LEGACY))
         drm_lastclose(dev);
 
     dev->registered = false;
 
     drm_client_dev_unregister(dev);
 
     if (drm_core_check_feature(dev, DRIVER_MODESET))
         drm_modeset_unregister_all(dev);
 
     if (dev->driver->unload)
         dev->driver->unload(dev);
 
     drm_legacy_pci_agp_destroy(dev);
     drm_legacy_rmmaps(dev);
 
     remove_compat_control_link(dev);
     drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
     drm_minor_unregister(dev, DRM_MINOR_RENDER);
 }
 EXPORT_SYMBOL(drm_dev_unregister);
 
 /**
  * drm_dev_set_unique - Set the unique name of a DRM device
  * @dev: device of which to set the unique name
  * @name: unique name
  *
  * Sets the unique name of a DRM device using the specified string. This is
  * already done by drm_dev_init(), drivers should only override the default
  * unique name for backwards compatibility reasons.
  *
  * Return: 0 on success or a negative error code on failure.
  */
 int drm_dev_set_unique(struct drm_device *dev, const char *name)
 {
     drmm_kfree(dev, dev->unique);
     dev->unique = drmm_kstrdup(dev, name, GFP_KERNEL);
 
     return dev->unique ? 0 : -ENOMEM;
 }
 EXPORT_SYMBOL(drm_dev_set_unique);
 
 /*
  * DRM Core
  * The DRM core module initializes all global DRM objects and makes them
  * available to drivers. Once setup, drivers can probe their respective
  * devices.
  * Currently, core management includes:
  *  - The "DRM-Global" key/value database
  *  - Global ID management for connectors
  *  - DRM major number allocation
  *  - DRM minor management
  *  - DRM sysfs class
  *  - DRM debugfs root
  *
  * Furthermore, the DRM core provides dynamic char-dev lookups. For each
  * interface registered on a DRM device, you can request minor numbers from DRM
  * core. DRM core takes care of major-number management and char-dev
  * registration. A stub ->open() callback forwards any open() requests to the
  * registered minor.
  */
 
 static int drm_stub_open(struct inode *inode, struct file *filp)
 {
     const struct file_operations *new_fops;
     struct drm_minor *minor;
     int err;
 
     DRM_DEBUG("\n");
 
     minor = drm_minor_acquire(iminor(inode));
     if (IS_ERR(minor))
         return PTR_ERR(minor);
 
     new_fops = fops_get(minor->dev->driver->fops);
     if (!new_fops) {
         err = -ENODEV;
         goto out;
     }
 
     replace_fops(filp, new_fops);
     if (filp->f_op->open)
         err = filp->f_op->open(inode, filp);
     else
         err = 0;
 
 out:
     drm_minor_release(minor);
 
     return err;
 }
 
 static const struct file_operations drm_stub_fops = {
     .owner = THIS_MODULE,
     .open = drm_stub_open,
     .llseek = noop_llseek,
 };
 
 static void drm_core_exit(void)
 {
     drm_privacy_screen_lookup_exit();
     unregister_chrdev(DRM_MAJOR, "drm");
     debugfs_remove(drm_debugfs_root);
     drm_sysfs_destroy();
     idr_destroy(&drm_minors_idr);
     drm_connector_ida_destroy();
 }
 
 static int __init drm_core_init(void)
 {
     int ret;
 
     drm_connector_ida_init();
     idr_init(&drm_minors_idr);
     drm_memcpy_init_early();
 
     ret = drm_sysfs_init();
     if (ret < 0) {
         DRM_ERROR("Cannot create DRM class: %d\n", ret);
         goto error;
     }
 
     drm_debugfs_root = debugfs_create_dir("dri", NULL);
 
     ret = register_chrdev(DRM_MAJOR, "drm", &drm_stub_fops);
     if (ret < 0)
         goto error;
 
     drm_privacy_screen_lookup_init();
 
     drm_core_init_complete = true;
 
     DRM_DEBUG("Initialized\n");
     return 0;
 
 error:
     drm_core_exit();
     return ret;
 }
 
 module_init(drm_core_init);
 module_exit(drm_core_exit);

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