drivers/gpu/drm/drm_gem_framebuffer_helper.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * drm gem framebuffer helper functions
  *
  * Copyright (C) 2017 Noralf Trønnes
  */

 #include <linux/dma-buf.h>
 #include <linux/dma-fence.h>
 #include <linux/reservation.h>
 #include <linux/slab.h>

 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_uapi.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_modeset_helper.h>
 #include <drm/drm_simple_kms_helper.h>

 /**
  * DOC: overview
  *
  * This library provides helpers for drivers that don't subclass
  * &drm_framebuffer and use &drm_gem_object for their backing storage.
  *
  * Drivers without additional needs to validate framebuffers can simply use
  * drm_gem_fb_create() and everything is wired up automatically. Other drivers
  * can use all parts independently.
  */

 /**
  * drm_gem_fb_get_obj() - Get GEM object backing the framebuffer
  * @fb: Framebuffer
  * @plane: Plane index
  *
  * No additional reference is taken beyond the one that the &drm_frambuffer
  * already holds.
  *
  * Returns:
  * Pointer to &drm_gem_object for the given framebuffer and plane index or NULL
  * if it does not exist.
  */
 struct drm_gem_object *drm_gem_fb_get_obj(struct drm_framebuffer *fb,
 					  unsigned int plane)
 {
 	if (plane >= 4)
 		return NULL;

 	return fb->obj[plane];
 }
 EXPORT_SYMBOL_GPL(drm_gem_fb_get_obj);

 static struct drm_framebuffer *
 drm_gem_fb_alloc(struct drm_device *dev,
 		 const struct drm_mode_fb_cmd2 *mode_cmd,
 		 struct drm_gem_object **obj, unsigned int num_planes,
 		 const struct drm_framebuffer_funcs *funcs)
 {
 	struct drm_framebuffer *fb;
 	int ret, i;

 	fb = kzalloc(sizeof(*fb), GFP_KERNEL);
 	if (!fb)
 		return ERR_PTR(-ENOMEM);

 	drm_helper_mode_fill_fb_struct(dev, fb, mode_cmd);

 	for (i = 0; i < num_planes; i++)
 		fb->obj[i] = obj[i];

 	ret = drm_framebuffer_init(dev, fb, funcs);
 	if (ret) {
 		DRM_DEV_ERROR(dev->dev, "Failed to init framebuffer: %d\n",
 			      ret);
 		kfree(fb);
 		return ERR_PTR(ret);
 	}

 	return fb;
 }

 /**
  * drm_gem_fb_destroy - Free GEM backed framebuffer
  * @fb: Framebuffer
  *
  * Frees a GEM backed framebuffer with its backing buffer(s) and the structure
  * itself. Drivers can use this as their &drm_framebuffer_funcs->destroy
  * callback.
  */
 void drm_gem_fb_destroy(struct drm_framebuffer *fb)
 {
 	int i;

 	for (i = 0; i < 4; i++)
 		drm_gem_object_put_unlocked(fb->obj[i]);

 	drm_framebuffer_cleanup(fb);
 	kfree(fb);
 }
 EXPORT_SYMBOL(drm_gem_fb_destroy);

 /**
  * drm_gem_fb_create_handle - Create handle for GEM backed framebuffer
  * @fb: Framebuffer
  * @file: DRM file to register the handle for
  * @handle: Pointer to return the created handle
  *
  * This function creates a handle for the GEM object backing the framebuffer.
  * Drivers can use this as their &drm_framebuffer_funcs->create_handle
  * callback. The GETFB IOCTL calls into this callback.
  *
  * Returns:
  * 0 on success or a negative error code on failure.
  */
 int drm_gem_fb_create_handle(struct drm_framebuffer *fb, struct drm_file *file,
 			     unsigned int *handle)
 {
 	return drm_gem_handle_create(file, fb->obj[0], handle);
 }
 EXPORT_SYMBOL(drm_gem_fb_create_handle);

 /**
  * drm_gem_fb_create_with_funcs() - Helper function for the
  *                                  &drm_mode_config_funcs.fb_create
  *                                  callback
  * @dev: DRM device
  * @file: DRM file that holds the GEM handle(s) backing the framebuffer
  * @mode_cmd: Metadata from the userspace framebuffer creation request
  * @funcs: vtable to be used for the new framebuffer object
  *
  * This function can be used to set &drm_framebuffer_funcs for drivers that need
  * custom framebuffer callbacks. Use drm_gem_fb_create() if you don't need to
  * change &drm_framebuffer_funcs. The function does buffer size validation.
  *
  * Returns:
  * Pointer to a &drm_framebuffer on success or an error pointer on failure.
  */
 struct drm_framebuffer *
 drm_gem_fb_create_with_funcs(struct drm_device *dev, struct drm_file *file,
 			     const struct drm_mode_fb_cmd2 *mode_cmd,
 			     const struct drm_framebuffer_funcs *funcs)
 {
 	const struct drm_format_info *info;
 	struct drm_gem_object *objs[4];
 	struct drm_framebuffer *fb;
 	int ret, i;

 	info = drm_get_format_info(dev, mode_cmd);
 	if (!info)
 		return ERR_PTR(-EINVAL);

 	for (i = 0; i < info->num_planes; i++) {
 		unsigned int width = mode_cmd->width / (i ? info->hsub : 1);
 		unsigned int height = mode_cmd->height / (i ? info->vsub : 1);
 		unsigned int min_size;

 		objs[i] = drm_gem_object_lookup(file, mode_cmd->handles[i]);
 		if (!objs[i]) {
 			DRM_DEBUG_KMS("Failed to lookup GEM object\n");
 			ret = -ENOENT;
 			goto err_gem_object_put;
 		}

 		min_size = (height - 1) * mode_cmd->pitches[i]
 			 + drm_format_info_min_pitch(info, i, width)
 			 + mode_cmd->offsets[i];

 		if (objs[i]->size < min_size) {
 			drm_gem_object_put_unlocked(objs[i]);
 			ret = -EINVAL;
 			goto err_gem_object_put;
 		}
 	}

 	fb = drm_gem_fb_alloc(dev, mode_cmd, objs, i, funcs);
 	if (IS_ERR(fb)) {
 		ret = PTR_ERR(fb);
 		goto err_gem_object_put;
 	}

 	return fb;

 err_gem_object_put:
 	for (i--; i >= 0; i--)
 		drm_gem_object_put_unlocked(objs[i]);

 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(drm_gem_fb_create_with_funcs);

 static const struct drm_framebuffer_funcs drm_gem_fb_funcs = {
 	.destroy	= drm_gem_fb_destroy,
 	.create_handle	= drm_gem_fb_create_handle,
 };

 /**
  * drm_gem_fb_create() - Helper function for the
  *                       &drm_mode_config_funcs.fb_create callback
  * @dev: DRM device
  * @file: DRM file that holds the GEM handle(s) backing the framebuffer
  * @mode_cmd: Metadata from the userspace framebuffer creation request
  *
  * This function creates a new framebuffer object described by
  * &drm_mode_fb_cmd2. This description includes handles for the buffer(s)
  * backing the framebuffer.
  *
  * If your hardware has special alignment or pitch requirements these should be
  * checked before calling this function. The function does buffer size
  * validation. Use drm_gem_fb_create_with_dirty() if you need framebuffer
  * flushing.
  *
  * Drivers can use this as their &drm_mode_config_funcs.fb_create callback.
  * The ADDFB2 IOCTL calls into this callback.
  *
  * Returns:
  * Pointer to a &drm_framebuffer on success or an error pointer on failure.
  */
 struct drm_framebuffer *
 drm_gem_fb_create(struct drm_device *dev, struct drm_file *file,
 		  const struct drm_mode_fb_cmd2 *mode_cmd)
 {
 	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
 					    &drm_gem_fb_funcs);
 }
 EXPORT_SYMBOL_GPL(drm_gem_fb_create);

 static const struct drm_framebuffer_funcs drm_gem_fb_funcs_dirtyfb = {
 	.destroy	= drm_gem_fb_destroy,
 	.create_handle	= drm_gem_fb_create_handle,
 	.dirty		= drm_atomic_helper_dirtyfb,
 };

 /**
  * drm_gem_fb_create_with_dirty() - Helper function for the
  *                       &drm_mode_config_funcs.fb_create callback
  * @dev: DRM device
  * @file: DRM file that holds the GEM handle(s) backing the framebuffer
  * @mode_cmd: Metadata from the userspace framebuffer creation request
  *
  * This function creates a new framebuffer object described by
  * &drm_mode_fb_cmd2. This description includes handles for the buffer(s)
  * backing the framebuffer. drm_atomic_helper_dirtyfb() is used for the dirty
  * callback giving framebuffer flushing through the atomic machinery. Use
  * drm_gem_fb_create() if you don't need the dirty callback.
  * The function does buffer size validation.
  *
  * Drivers should also call drm_plane_enable_fb_damage_clips() on all planes
  * to enable userspace to use damage clips also with the ATOMIC IOCTL.
  *
  * Drivers can use this as their &drm_mode_config_funcs.fb_create callback.
  * The ADDFB2 IOCTL calls into this callback.
  *
  * Returns:
  * Pointer to a &drm_framebuffer on success or an error pointer on failure.
  */
 struct drm_framebuffer *
 drm_gem_fb_create_with_dirty(struct drm_device *dev, struct drm_file *file,
 			     const struct drm_mode_fb_cmd2 *mode_cmd)
 {
 	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
 					    &drm_gem_fb_funcs_dirtyfb);
 }
 EXPORT_SYMBOL_GPL(drm_gem_fb_create_with_dirty);

 /**
  * drm_gem_fb_prepare_fb() - Prepare a GEM backed framebuffer
  * @plane: Plane
  * @state: Plane state the fence will be attached to
  *
  * This function prepares a GEM backed framebuffer for scanout by checking if
  * the plane framebuffer has a DMA-BUF attached. If it does, it extracts the
  * exclusive fence and attaches it to the plane state for the atomic helper to
  * wait on. This function can be used as the &drm_plane_helper_funcs.prepare_fb
  * callback.
  *
  * There is no need for &drm_plane_helper_funcs.cleanup_fb hook for simple
  * gem based framebuffer drivers which have their buffers always pinned in
  * memory.
  *
  * See drm_atomic_set_fence_for_plane() for a discussion of implicit and
  * explicit fencing in atomic modeset updates.
  */
 int drm_gem_fb_prepare_fb(struct drm_plane *plane,
 			  struct drm_plane_state *state)
 {
 	struct dma_buf *dma_buf;
 	struct dma_fence *fence;

 	if (!state->fb)
 		return 0;

 	dma_buf = drm_gem_fb_get_obj(state->fb, 0)->dma_buf;
 	if (dma_buf) {
 		fence = reservation_object_get_excl_rcu(dma_buf->resv);
 		drm_atomic_set_fence_for_plane(state, fence);
 	}

 	return 0;
 }
 EXPORT_SYMBOL_GPL(drm_gem_fb_prepare_fb);

 /**
  * drm_gem_fb_simple_display_pipe_prepare_fb - prepare_fb helper for
  *     &drm_simple_display_pipe
  * @pipe: Simple display pipe
  * @plane_state: Plane state
  *
  * This function uses drm_gem_fb_prepare_fb() to check if the plane FB has a
  * &dma_buf attached, extracts the exclusive fence and attaches it to plane
  * state for the atomic helper to wait on. Drivers can use this as their
  * &drm_simple_display_pipe_funcs.prepare_fb callback.
  *
  * See drm_atomic_set_fence_for_plane() for a discussion of implicit and
  * explicit fencing in atomic modeset updates.
  */
 int drm_gem_fb_simple_display_pipe_prepare_fb(struct drm_simple_display_pipe *pipe,
 					      struct drm_plane_state *plane_state)
 {
 	return drm_gem_fb_prepare_fb(&pipe->plane, plane_state);
 }
 EXPORT_SYMBOL(drm_gem_fb_simple_display_pipe_prepare_fb);

 /**
  * drm_gem_fbdev_fb_create - Create a GEM backed &drm_framebuffer for fbdev
  *                           emulation
  * @dev: DRM device
  * @sizes: fbdev size description
  * @pitch_align: Optional pitch alignment
  * @obj: GEM object backing the framebuffer
  * @funcs: Optional vtable to be used for the new framebuffer object when the
  *         dirty callback is needed.
  *
  * This function creates a framebuffer from a &drm_fb_helper_surface_size
  * description for use in the &drm_fb_helper_funcs.fb_probe callback.
  *
  * Returns:
  * Pointer to a &drm_framebuffer on success or an error pointer on failure.
  */
 struct drm_framebuffer *
 drm_gem_fbdev_fb_create(struct drm_device *dev,
 			struct drm_fb_helper_surface_size *sizes,
 			unsigned int pitch_align, struct drm_gem_object *obj,
 			const struct drm_framebuffer_funcs *funcs)
 {
 	struct drm_mode_fb_cmd2 mode_cmd = { 0 };

 	mode_cmd.width = sizes->surface_width;
 	mode_cmd.height = sizes->surface_height;
 	mode_cmd.pitches[0] = sizes->surface_width *
 			      DIV_ROUND_UP(sizes->surface_bpp, 8);
 	if (pitch_align)
 		mode_cmd.pitches[0] = roundup(mode_cmd.pitches[0],
 					      pitch_align);
 	mode_cmd.pixel_format = drm_driver_legacy_fb_format(dev, sizes->surface_bpp,
 							    sizes->surface_depth);
 	if (obj->size < mode_cmd.pitches[0] * mode_cmd.height)
 		return ERR_PTR(-EINVAL);

 	if (!funcs)
 		funcs = &drm_gem_fb_funcs;

 	return drm_gem_fb_alloc(dev, &mode_cmd, &obj, 1, funcs);
 }
 EXPORT_SYMBOL(drm_gem_fbdev_fb_create);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* drm gem framebuffer helper functions
	*
	* Copyright (C) 2017 Noralf Trønnes
	*/

	#include <linux/dma-buf.h>
	#include <linux/dma-fence.h>
	#include <linux/reservation.h>
	#include <linux/slab.h>

	#include <drm/drm_atomic.h>
	#include <drm/drm_atomic_uapi.h>
	#include <drm/drm_damage_helper.h>
	#include <drm/drm_fb_helper.h>
	#include <drm/drm_fourcc.h>
	#include <drm/drm_framebuffer.h>
	#include <drm/drm_gem.h>
	#include <drm/drm_gem_framebuffer_helper.h>
	#include <drm/drm_modeset_helper.h>
	#include <drm/drm_simple_kms_helper.h>

	/**
	* DOC: overview
	*
	* This library provides helpers for drivers that don't subclass
	* &drm_framebuffer and use &drm_gem_object for their backing storage.
	*
	* Drivers without additional needs to validate framebuffers can simply use
	* drm_gem_fb_create() and everything is wired up automatically. Other drivers
	* can use all parts independently.
	*/

	/**
	* drm_gem_fb_get_obj() - Get GEM object backing the framebuffer
	* @fb: Framebuffer
	* @plane: Plane index
	*
	* No additional reference is taken beyond the one that the &drm_frambuffer
	* already holds.
	*
	* Returns:
	* Pointer to &drm_gem_object for the given framebuffer and plane index or NULL
	* if it does not exist.
	*/
	struct drm_gem_object drm_gem_fb_get_obj(struct drm_framebuffer fb,
	unsigned int plane)
	{
	if (plane >= 4)
	return NULL;

	return fb->obj[plane];
	}
	EXPORT_SYMBOL_GPL(drm_gem_fb_get_obj);

	static struct drm_framebuffer *
	drm_gem_fb_alloc(struct drm_device *dev,
	const struct drm_mode_fb_cmd2 *mode_cmd,
	struct drm_gem_object **obj, unsigned int num_planes,
	const struct drm_framebuffer_funcs *funcs)
	{
	struct drm_framebuffer *fb;
	int ret, i;

	fb = kzalloc(sizeof(*fb), GFP_KERNEL);
	if (!fb)
	return ERR_PTR(-ENOMEM);

	drm_helper_mode_fill_fb_struct(dev, fb, mode_cmd);

	for (i = 0; i < num_planes; i++)
	fb->obj[i] = obj[i];

	ret = drm_framebuffer_init(dev, fb, funcs);
	if (ret) {
	DRM_DEV_ERROR(dev->dev, "Failed to init framebuffer: %d\n",
	ret);
	kfree(fb);
	return ERR_PTR(ret);
	}

	return fb;
	}

	/**
	* drm_gem_fb_destroy - Free GEM backed framebuffer
	* @fb: Framebuffer
	*
	* Frees a GEM backed framebuffer with its backing buffer(s) and the structure
	* itself. Drivers can use this as their &drm_framebuffer_funcs->destroy
	* callback.
	*/
	void drm_gem_fb_destroy(struct drm_framebuffer *fb)
	{
	int i;

	for (i = 0; i < 4; i++)
	drm_gem_object_put_unlocked(fb->obj[i]);

	drm_framebuffer_cleanup(fb);
	kfree(fb);
	}
	EXPORT_SYMBOL(drm_gem_fb_destroy);

	/**
	* drm_gem_fb_create_handle - Create handle for GEM backed framebuffer
	* @fb: Framebuffer
	* @file: DRM file to register the handle for
	* @handle: Pointer to return the created handle
	*
	* This function creates a handle for the GEM object backing the framebuffer.
	* Drivers can use this as their &drm_framebuffer_funcs->create_handle
	* callback. The GETFB IOCTL calls into this callback.
	*
	* Returns:
	* 0 on success or a negative error code on failure.
	*/
	int drm_gem_fb_create_handle(struct drm_framebuffer fb, struct drm_file file,
	unsigned int *handle)
	{
	return drm_gem_handle_create(file, fb->obj[0], handle);
	}
	EXPORT_SYMBOL(drm_gem_fb_create_handle);

	/**
	* drm_gem_fb_create_with_funcs() - Helper function for the
	* &drm_mode_config_funcs.fb_create
	* callback
	* @dev: DRM device
	* @file: DRM file that holds the GEM handle(s) backing the framebuffer
	* @mode_cmd: Metadata from the userspace framebuffer creation request
	* @funcs: vtable to be used for the new framebuffer object
	*
	* This function can be used to set &drm_framebuffer_funcs for drivers that need
	* custom framebuffer callbacks. Use drm_gem_fb_create() if you don't need to
	* change &drm_framebuffer_funcs. The function does buffer size validation.
	*
	* Returns:
	* Pointer to a &drm_framebuffer on success or an error pointer on failure.
	*/
	struct drm_framebuffer *
	drm_gem_fb_create_with_funcs(struct drm_device dev, struct drm_file file,
	const struct drm_mode_fb_cmd2 *mode_cmd,
	const struct drm_framebuffer_funcs *funcs)
	{
	const struct drm_format_info *info;
	struct drm_gem_object *objs[4];
	struct drm_framebuffer *fb;
	int ret, i;

	info = drm_get_format_info(dev, mode_cmd);
	if (!info)
	return ERR_PTR(-EINVAL);

	for (i = 0; i < info->num_planes; i++) {
	unsigned int width = mode_cmd->width / (i ? info->hsub : 1);
	unsigned int height = mode_cmd->height / (i ? info->vsub : 1);
	unsigned int min_size;

	objs[i] = drm_gem_object_lookup(file, mode_cmd->handles[i]);
	if (!objs[i]) {
	DRM_DEBUG_KMS("Failed to lookup GEM object\n");
	ret = -ENOENT;
	goto err_gem_object_put;
	}

	min_size = (height - 1) * mode_cmd->pitches[i]
	+ drm_format_info_min_pitch(info, i, width)
	+ mode_cmd->offsets[i];

	if (objs[i]->size < min_size) {
	drm_gem_object_put_unlocked(objs[i]);
	ret = -EINVAL;
	goto err_gem_object_put;
	}
	}

	fb = drm_gem_fb_alloc(dev, mode_cmd, objs, i, funcs);
	if (IS_ERR(fb)) {
	ret = PTR_ERR(fb);
	goto err_gem_object_put;
	}

	return fb;

	err_gem_object_put:
	for (i--; i >= 0; i--)
	drm_gem_object_put_unlocked(objs[i]);

	return ERR_PTR(ret);
	}
	EXPORT_SYMBOL_GPL(drm_gem_fb_create_with_funcs);

	static const struct drm_framebuffer_funcs drm_gem_fb_funcs = {
	.destroy = drm_gem_fb_destroy,
	.create_handle = drm_gem_fb_create_handle,
	};

	/**
	* drm_gem_fb_create() - Helper function for the
	* &drm_mode_config_funcs.fb_create callback
	* @dev: DRM device
	* @file: DRM file that holds the GEM handle(s) backing the framebuffer
	* @mode_cmd: Metadata from the userspace framebuffer creation request
	*
	* This function creates a new framebuffer object described by
	* &drm_mode_fb_cmd2. This description includes handles for the buffer(s)
	* backing the framebuffer.
	*
	* If your hardware has special alignment or pitch requirements these should be
	* checked before calling this function. The function does buffer size
	* validation. Use drm_gem_fb_create_with_dirty() if you need framebuffer
	* flushing.
	*
	* Drivers can use this as their &drm_mode_config_funcs.fb_create callback.
	* The ADDFB2 IOCTL calls into this callback.
	*
	* Returns:
	* Pointer to a &drm_framebuffer on success or an error pointer on failure.
	*/
	struct drm_framebuffer *
	drm_gem_fb_create(struct drm_device dev, struct drm_file file,
	const struct drm_mode_fb_cmd2 *mode_cmd)
	{
	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
	&drm_gem_fb_funcs);
	}
	EXPORT_SYMBOL_GPL(drm_gem_fb_create);

	static const struct drm_framebuffer_funcs drm_gem_fb_funcs_dirtyfb = {
	.destroy = drm_gem_fb_destroy,
	.create_handle = drm_gem_fb_create_handle,
	.dirty = drm_atomic_helper_dirtyfb,
	};

	/**
	* drm_gem_fb_create_with_dirty() - Helper function for the
	* &drm_mode_config_funcs.fb_create callback
	* @dev: DRM device
	* @file: DRM file that holds the GEM handle(s) backing the framebuffer
	* @mode_cmd: Metadata from the userspace framebuffer creation request
	*
	* This function creates a new framebuffer object described by
	* &drm_mode_fb_cmd2. This description includes handles for the buffer(s)
	* backing the framebuffer. drm_atomic_helper_dirtyfb() is used for the dirty
	* callback giving framebuffer flushing through the atomic machinery. Use
	* drm_gem_fb_create() if you don't need the dirty callback.
	* The function does buffer size validation.
	*
	* Drivers should also call drm_plane_enable_fb_damage_clips() on all planes
	* to enable userspace to use damage clips also with the ATOMIC IOCTL.
	*
	* Drivers can use this as their &drm_mode_config_funcs.fb_create callback.
	* The ADDFB2 IOCTL calls into this callback.
	*
	* Returns:
	* Pointer to a &drm_framebuffer on success or an error pointer on failure.
	*/
	struct drm_framebuffer *
	drm_gem_fb_create_with_dirty(struct drm_device dev, struct drm_file file,
	const struct drm_mode_fb_cmd2 *mode_cmd)
	{
	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
	&drm_gem_fb_funcs_dirtyfb);
	}
	EXPORT_SYMBOL_GPL(drm_gem_fb_create_with_dirty);

	/**
	* drm_gem_fb_prepare_fb() - Prepare a GEM backed framebuffer
	* @plane: Plane
	* @state: Plane state the fence will be attached to
	*
	* This function prepares a GEM backed framebuffer for scanout by checking if
	* the plane framebuffer has a DMA-BUF attached. If it does, it extracts the
	* exclusive fence and attaches it to the plane state for the atomic helper to
	* wait on. This function can be used as the &drm_plane_helper_funcs.prepare_fb
	* callback.
	*
	* There is no need for &drm_plane_helper_funcs.cleanup_fb hook for simple
	* gem based framebuffer drivers which have their buffers always pinned in
	* memory.
	*
	* See drm_atomic_set_fence_for_plane() for a discussion of implicit and
	* explicit fencing in atomic modeset updates.
	*/
	int drm_gem_fb_prepare_fb(struct drm_plane *plane,
	struct drm_plane_state *state)
	{
	struct dma_buf *dma_buf;
	struct dma_fence *fence;

	if (!state->fb)
	return 0;

	dma_buf = drm_gem_fb_get_obj(state->fb, 0)->dma_buf;
	if (dma_buf) {
	fence = reservation_object_get_excl_rcu(dma_buf->resv);
	drm_atomic_set_fence_for_plane(state, fence);
	}

	return 0;
	}
	EXPORT_SYMBOL_GPL(drm_gem_fb_prepare_fb);

	/**
	* drm_gem_fb_simple_display_pipe_prepare_fb - prepare_fb helper for
	* &drm_simple_display_pipe
	* @pipe: Simple display pipe
	* @plane_state: Plane state
	*
	* This function uses drm_gem_fb_prepare_fb() to check if the plane FB has a
	* &dma_buf attached, extracts the exclusive fence and attaches it to plane
	* state for the atomic helper to wait on. Drivers can use this as their
	* &drm_simple_display_pipe_funcs.prepare_fb callback.
	*
	* See drm_atomic_set_fence_for_plane() for a discussion of implicit and
	* explicit fencing in atomic modeset updates.
	*/
	int drm_gem_fb_simple_display_pipe_prepare_fb(struct drm_simple_display_pipe *pipe,
	struct drm_plane_state *plane_state)
	{
	return drm_gem_fb_prepare_fb(&pipe->plane, plane_state);
	}
	EXPORT_SYMBOL(drm_gem_fb_simple_display_pipe_prepare_fb);

	/**
	* drm_gem_fbdev_fb_create - Create a GEM backed &drm_framebuffer for fbdev
	* emulation
	* @dev: DRM device
	* @sizes: fbdev size description
	* @pitch_align: Optional pitch alignment
	* @obj: GEM object backing the framebuffer
	* @funcs: Optional vtable to be used for the new framebuffer object when the
	* dirty callback is needed.
	*
	* This function creates a framebuffer from a &drm_fb_helper_surface_size
	* description for use in the &drm_fb_helper_funcs.fb_probe callback.
	*
	* Returns:
	* Pointer to a &drm_framebuffer on success or an error pointer on failure.
	*/
	struct drm_framebuffer *
	drm_gem_fbdev_fb_create(struct drm_device *dev,
	struct drm_fb_helper_surface_size *sizes,
	unsigned int pitch_align, struct drm_gem_object *obj,
	const struct drm_framebuffer_funcs *funcs)
	{
	struct drm_mode_fb_cmd2 mode_cmd = { 0 };

	mode_cmd.width = sizes->surface_width;
	mode_cmd.height = sizes->surface_height;
	mode_cmd.pitches[0] = sizes->surface_width *
	DIV_ROUND_UP(sizes->surface_bpp, 8);
	if (pitch_align)
	mode_cmd.pitches[0] = roundup(mode_cmd.pitches[0],
	pitch_align);
	mode_cmd.pixel_format = drm_driver_legacy_fb_format(dev, sizes->surface_bpp,
	sizes->surface_depth);
	if (obj->size < mode_cmd.pitches[0] * mode_cmd.height)
	return ERR_PTR(-EINVAL);

	if (!funcs)
	funcs = &drm_gem_fb_funcs;

	return drm_gem_fb_alloc(dev, &mode_cmd, &obj, 1, funcs);
	}
	EXPORT_SYMBOL(drm_gem_fbdev_fb_create);