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/slab.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>

 #define AFBC_HEADER_SIZE		16
 #define AFBC_TH_LAYOUT_ALIGNMENT	8
 #define AFBC_HDR_ALIGN			64
 #define AFBC_SUPERBLOCK_PIXELS		256
 #define AFBC_SUPERBLOCK_ALIGNMENT	128
 #define AFBC_TH_BODY_START_ALIGNMENT	4096

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

 	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_err(dev, "Failed to init framebuffer: %d\n", ret);

 	return ret;
 }

 /**
  * 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(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_init_with_funcs() - Helper function for implementing
  *				  &drm_mode_config_funcs.fb_create
  *				  callback in cases when the driver
  *				  allocates a subclass of
  *				  struct drm_framebuffer
  * @dev: DRM device
  * @fb: framebuffer object
  * @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.
  * The buffer size validation is for a general case, though, so users should
  * pay attention to the checks being appropriate for them or, at least,
  * non-conflicting.
  *
  * Returns:
  * Zero or a negative error code.
  */
 int drm_gem_fb_init_with_funcs(struct drm_device *dev,
 			       struct drm_framebuffer *fb,
 			       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];
 	int ret, i;

 	info = drm_get_format_info(dev, mode_cmd);
 	if (!info)
 		return -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_dbg_kms(dev, "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(objs[i]);
 			ret = -EINVAL;
 			goto err_gem_object_put;
 		}
 	}

 	ret = drm_gem_fb_init(dev, fb, mode_cmd, objs, i, funcs);
 	if (ret)
 		goto err_gem_object_put;

 	return 0;

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

 	return ret;
 }
 EXPORT_SYMBOL_GPL(drm_gem_fb_init_with_funcs);

 /**
  * 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)
 {
 	struct drm_framebuffer *fb;
 	int ret;

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

 	ret = drm_gem_fb_init_with_funcs(dev, fb, file, mode_cmd, funcs);
 	if (ret) {
 		kfree(fb);
 		return ERR_PTR(ret);
 	}

 	return fb;
 }
 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);

 static __u32 drm_gem_afbc_get_bpp(struct drm_device *dev,
 				  const struct drm_mode_fb_cmd2 *mode_cmd)
 {
 	const struct drm_format_info *info;

 	info = drm_get_format_info(dev, mode_cmd);

 	/* use whatever a driver has set */
 	if (info->cpp[0])
 		return info->cpp[0] * 8;

 	/* guess otherwise */
 	switch (info->format) {
 	case DRM_FORMAT_YUV420_8BIT:
 		return 12;
 	case DRM_FORMAT_YUV420_10BIT:
 		return 15;
 	case DRM_FORMAT_VUY101010:
 		return 30;
 	default:
 		break;
 	}

 	/* all attempts failed */
 	return 0;
 }

 static int drm_gem_afbc_min_size(struct drm_device *dev,
 				 const struct drm_mode_fb_cmd2 *mode_cmd,
 				 struct drm_afbc_framebuffer *afbc_fb)
 {
 	__u32 n_blocks, w_alignment, h_alignment, hdr_alignment;
 	/* remove bpp when all users properly encode cpp in drm_format_info */
 	__u32 bpp;

 	switch (mode_cmd->modifier[0] & AFBC_FORMAT_MOD_BLOCK_SIZE_MASK) {
 	case AFBC_FORMAT_MOD_BLOCK_SIZE_16x16:
 		afbc_fb->block_width = 16;
 		afbc_fb->block_height = 16;
 		break;
 	case AFBC_FORMAT_MOD_BLOCK_SIZE_32x8:
 		afbc_fb->block_width = 32;
 		afbc_fb->block_height = 8;
 		break;
 	/* no user exists yet - fall through */
 	case AFBC_FORMAT_MOD_BLOCK_SIZE_64x4:
 	case AFBC_FORMAT_MOD_BLOCK_SIZE_32x8_64x4:
 	default:
 		drm_dbg_kms(dev, "Invalid AFBC_FORMAT_MOD_BLOCK_SIZE: %lld.\n",
 			    mode_cmd->modifier[0]
 			    & AFBC_FORMAT_MOD_BLOCK_SIZE_MASK);
 		return -EINVAL;
 	}

 	/* tiled header afbc */
 	w_alignment = afbc_fb->block_width;
 	h_alignment = afbc_fb->block_height;
 	hdr_alignment = AFBC_HDR_ALIGN;
 	if (mode_cmd->modifier[0] & AFBC_FORMAT_MOD_TILED) {
 		w_alignment *= AFBC_TH_LAYOUT_ALIGNMENT;
 		h_alignment *= AFBC_TH_LAYOUT_ALIGNMENT;
 		hdr_alignment = AFBC_TH_BODY_START_ALIGNMENT;
 	}

 	afbc_fb->aligned_width = ALIGN(mode_cmd->width, w_alignment);
 	afbc_fb->aligned_height = ALIGN(mode_cmd->height, h_alignment);
 	afbc_fb->offset = mode_cmd->offsets[0];

 	bpp = drm_gem_afbc_get_bpp(dev, mode_cmd);
 	if (!bpp) {
 		drm_dbg_kms(dev, "Invalid AFBC bpp value: %d\n", bpp);
 		return -EINVAL;
 	}

 	n_blocks = (afbc_fb->aligned_width * afbc_fb->aligned_height)
 		   / AFBC_SUPERBLOCK_PIXELS;
 	afbc_fb->afbc_size = ALIGN(n_blocks * AFBC_HEADER_SIZE, hdr_alignment);
 	afbc_fb->afbc_size += n_blocks * ALIGN(bpp * AFBC_SUPERBLOCK_PIXELS / 8,
 					       AFBC_SUPERBLOCK_ALIGNMENT);

 	return 0;
 }

 /**
  * drm_gem_fb_afbc_init() - Helper function for drivers using afbc to
  *			    fill and validate all the afbc-specific
  *			    struct drm_afbc_framebuffer members
  *
  * @dev: DRM device
  * @afbc_fb: afbc-specific framebuffer
  * @mode_cmd: Metadata from the userspace framebuffer creation request
  * @afbc_fb: afbc framebuffer
  *
  * This function can be used by drivers which support afbc to complete
  * the preparation of struct drm_afbc_framebuffer. It must be called after
  * allocating the said struct and calling drm_gem_fb_init_with_funcs().
  * It is caller's responsibility to put afbc_fb->base.obj objects in case
  * the call is unsuccessful.
  *
  * Returns:
  * Zero on success or a negative error value on failure.
  */
 int drm_gem_fb_afbc_init(struct drm_device *dev,
 			 const struct drm_mode_fb_cmd2 *mode_cmd,
 			 struct drm_afbc_framebuffer *afbc_fb)
 {
 	const struct drm_format_info *info;
 	struct drm_gem_object **objs;
 	int ret;

 	objs = afbc_fb->base.obj;
 	info = drm_get_format_info(dev, mode_cmd);
 	if (!info)
 		return -EINVAL;

 	ret = drm_gem_afbc_min_size(dev, mode_cmd, afbc_fb);
 	if (ret < 0)
 		return ret;

 	if (objs[0]->size < afbc_fb->afbc_size)
 		return -EINVAL;

 	return 0;
 }
 EXPORT_SYMBOL_GPL(drm_gem_fb_afbc_init);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* drm gem framebuffer helper functions
	*
	* Copyright (C) 2017 Noralf Trønnes
	*/

	#include <linux/slab.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>

	#define AFBC_HEADER_SIZE 16
	#define AFBC_TH_LAYOUT_ALIGNMENT 8
	#define AFBC_HDR_ALIGN 64
	#define AFBC_SUPERBLOCK_PIXELS 256
	#define AFBC_SUPERBLOCK_ALIGNMENT 128
	#define AFBC_TH_BODY_START_ALIGNMENT 4096

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

	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_err(dev, "Failed to init framebuffer: %d\n", ret);

	return ret;
	}

	/**
	* 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(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_init_with_funcs() - Helper function for implementing
	* &drm_mode_config_funcs.fb_create
	* callback in cases when the driver
	* allocates a subclass of
	* struct drm_framebuffer
	* @dev: DRM device
	* @fb: framebuffer object
	* @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.
	* The buffer size validation is for a general case, though, so users should
	* pay attention to the checks being appropriate for them or, at least,
	* non-conflicting.
	*
	* Returns:
	* Zero or a negative error code.
	*/
	int drm_gem_fb_init_with_funcs(struct drm_device *dev,
	struct drm_framebuffer *fb,
	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];
	int ret, i;

	info = drm_get_format_info(dev, mode_cmd);
	if (!info)
	return -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_dbg_kms(dev, "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(objs[i]);
	ret = -EINVAL;
	goto err_gem_object_put;
	}
	}

	ret = drm_gem_fb_init(dev, fb, mode_cmd, objs, i, funcs);
	if (ret)
	goto err_gem_object_put;

	return 0;

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

	return ret;
	}
	EXPORT_SYMBOL_GPL(drm_gem_fb_init_with_funcs);

	/**
	* 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)
	{
	struct drm_framebuffer *fb;
	int ret;

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

	ret = drm_gem_fb_init_with_funcs(dev, fb, file, mode_cmd, funcs);
	if (ret) {
	kfree(fb);
	return ERR_PTR(ret);
	}

	return fb;
	}
	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);

	static __u32 drm_gem_afbc_get_bpp(struct drm_device *dev,
	const struct drm_mode_fb_cmd2 *mode_cmd)
	{
	const struct drm_format_info *info;

	info = drm_get_format_info(dev, mode_cmd);

	/* use whatever a driver has set */
	if (info->cpp[0])
	return info->cpp[0] * 8;

	/* guess otherwise */
	switch (info->format) {
	case DRM_FORMAT_YUV420_8BIT:
	return 12;
	case DRM_FORMAT_YUV420_10BIT:
	return 15;
	case DRM_FORMAT_VUY101010:
	return 30;
	default:
	break;
	}

	/* all attempts failed */
	return 0;
	}

	static int drm_gem_afbc_min_size(struct drm_device *dev,
	const struct drm_mode_fb_cmd2 *mode_cmd,
	struct drm_afbc_framebuffer *afbc_fb)
	{
	__u32 n_blocks, w_alignment, h_alignment, hdr_alignment;
	/* remove bpp when all users properly encode cpp in drm_format_info */
	__u32 bpp;

	switch (mode_cmd->modifier[0] & AFBC_FORMAT_MOD_BLOCK_SIZE_MASK) {
	case AFBC_FORMAT_MOD_BLOCK_SIZE_16x16:
	afbc_fb->block_width = 16;
	afbc_fb->block_height = 16;
	break;
	case AFBC_FORMAT_MOD_BLOCK_SIZE_32x8:
	afbc_fb->block_width = 32;
	afbc_fb->block_height = 8;
	break;
	/* no user exists yet - fall through */
	case AFBC_FORMAT_MOD_BLOCK_SIZE_64x4:
	case AFBC_FORMAT_MOD_BLOCK_SIZE_32x8_64x4:
	default:
	drm_dbg_kms(dev, "Invalid AFBC_FORMAT_MOD_BLOCK_SIZE: %lld.\n",
	mode_cmd->modifier[0]
	& AFBC_FORMAT_MOD_BLOCK_SIZE_MASK);
	return -EINVAL;
	}

	/* tiled header afbc */
	w_alignment = afbc_fb->block_width;
	h_alignment = afbc_fb->block_height;
	hdr_alignment = AFBC_HDR_ALIGN;
	if (mode_cmd->modifier[0] & AFBC_FORMAT_MOD_TILED) {
	w_alignment *= AFBC_TH_LAYOUT_ALIGNMENT;
	h_alignment *= AFBC_TH_LAYOUT_ALIGNMENT;
	hdr_alignment = AFBC_TH_BODY_START_ALIGNMENT;
	}

	afbc_fb->aligned_width = ALIGN(mode_cmd->width, w_alignment);
	afbc_fb->aligned_height = ALIGN(mode_cmd->height, h_alignment);
	afbc_fb->offset = mode_cmd->offsets[0];

	bpp = drm_gem_afbc_get_bpp(dev, mode_cmd);
	if (!bpp) {
	drm_dbg_kms(dev, "Invalid AFBC bpp value: %d\n", bpp);
	return -EINVAL;
	}

	n_blocks = (afbc_fb->aligned_width * afbc_fb->aligned_height)
	/ AFBC_SUPERBLOCK_PIXELS;
	afbc_fb->afbc_size = ALIGN(n_blocks * AFBC_HEADER_SIZE, hdr_alignment);
	afbc_fb->afbc_size += n_blocks * ALIGN(bpp * AFBC_SUPERBLOCK_PIXELS / 8,
	AFBC_SUPERBLOCK_ALIGNMENT);

	return 0;
	}

	/**
	* drm_gem_fb_afbc_init() - Helper function for drivers using afbc to
	* fill and validate all the afbc-specific
	* struct drm_afbc_framebuffer members
	*
	* @dev: DRM device
	* @afbc_fb: afbc-specific framebuffer
	* @mode_cmd: Metadata from the userspace framebuffer creation request
	* @afbc_fb: afbc framebuffer
	*
	* This function can be used by drivers which support afbc to complete
	* the preparation of struct drm_afbc_framebuffer. It must be called after
	* allocating the said struct and calling drm_gem_fb_init_with_funcs().
	* It is caller's responsibility to put afbc_fb->base.obj objects in case
	* the call is unsuccessful.
	*
	* Returns:
	* Zero on success or a negative error value on failure.
	*/
	int drm_gem_fb_afbc_init(struct drm_device *dev,
	const struct drm_mode_fb_cmd2 *mode_cmd,
	struct drm_afbc_framebuffer *afbc_fb)
	{
	const struct drm_format_info *info;
	struct drm_gem_object **objs;
	int ret;

	objs = afbc_fb->base.obj;
	info = drm_get_format_info(dev, mode_cmd);
	if (!info)
	return -EINVAL;

	ret = drm_gem_afbc_min_size(dev, mode_cmd, afbc_fb);
	if (ret < 0)
	return ret;

	if (objs[0]->size < afbc_fb->afbc_size)
	return -EINVAL;

	return 0;
	}
	EXPORT_SYMBOL_GPL(drm_gem_fb_afbc_init);