drm/fourcc: Add char_per_block, block_w and block_h in drm_format_info

For some pixel formats .cpp structure in drm_format info it's not
enough to describe the peculiarities of the pixel layout, for example
tiled formats or packed formats at bit level.

What's implemented here is to add three new members to drm_format_info
that could describe such formats:

- char_per_block[3]
- block_w[3]
- block_h[3]

char_per_block will be put in a union alongside cpp, for transparent
compatibility  with the existing format descriptions.

Regarding, block_w and block_h they are intended to be used through
their equivalent getters drm_format_info_block_width /
drm_format_info_block_height, the reason of the getters is to abstract
the fact that for normal formats block_w and block_h will be unset/0,
but the methods will be returning 1.

Additionally, convenience function drm_format_info_min_pitch had been
added that computes the minimum required pitch for a given pixel
format and buffer width.

Using that the following drm core functions had been updated to
generically handle both block and non-block formats:

- drm_fb_cma_get_gem_addr: for block formats it will just return the
  beginning of the block.
- framebuffer_check: Use the newly added drm_format_info_min_pitch.
- drm_gem_fb_create_with_funcs: Use the newly added
  drm_format_info_min_pitch.
- In places where is not expecting to handle block formats, like fbdev
  helpers I just added some warnings in case the block width/height
  are greater than 1.

Changes since v3:
 - Add helper function for computing the minimum required pitch.
 - Improve/cleanup documentation

Changes since v8:
 - Fixed build on 32bits arm architectures, with:

-       return DIV_ROUND_UP((u64)buffer_width * info->char_per_block[plane],
+       return DIV_ROUND_UP_ULL((u64)buffer_width * info->char_per_block[plane],

Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181101170055.5433-1-alexandru-cosmin.gheorghe@arm.com

1 files changed, 59 insertions, 2 deletions

diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
index 345f11227e9e..bcb389f04618 100644
--- a/include/drm/drm_fourcc.h
+++ b/include/drm/drm_fourcc.h
@@ -69,8 +69,59 @@ struct drm_format_info {
 	/** @num_planes: Number of color planes (1 to 3) */
 	u8 num_planes;
 
-	/** @cpp: Number of bytes per pixel (per plane) */
-	u8 cpp[3];
+	union {
+		/**
+		 * @cpp:
+		 *
+		 * Number of bytes per pixel (per plane), this is aliased with
+		 * @char_per_block. It is deprecated in favour of using the
+		 * triplet @char_per_block, @block_w, @block_h for better
+		 * describing the pixel format.
+		 */
+		u8 cpp[3];
+
+		/**
+		 * @char_per_block:
+		 *
+		 * Number of bytes per block (per plane), where blocks are
+		 * defined as a rectangle of pixels which are stored next to
+		 * each other in a byte aligned memory region. Together with
+		 * @block_w and @block_h this is used to properly describe tiles
+		 * in tiled formats or to describe groups of pixels in packed
+		 * formats for which the memory needed for a single pixel is not
+		 * byte aligned.
+		 *
+		 * @cpp has been kept for historical reasons because there are
+		 * a lot of places in drivers where it's used. In drm core for
+		 * generic code paths the preferred way is to use
+		 * @char_per_block, drm_format_info_block_width() and
+		 * drm_format_info_block_height() which allows handling both
+		 * block and non-block formats in the same way.
+		 *
+		 * For formats that are intended to be used only with non-linear
+		 * modifiers both @cpp and @char_per_block must be 0 in the
+		 * generic format table. Drivers could supply accurate
+		 * information from their drm_mode_config.get_format_info hook
+		 * if they want the core to be validating the pitch.
+		 */
+		u8 char_per_block[3];
+	};
+
+	/**
+	 * @block_w:
+	 *
+	 * Block width in pixels, this is intended to be accessed through
+	 * drm_format_info_block_width()
+	 */
+	u8 block_w[3];
+
+	/**
+	 * @block_h:
+	 *
+	 * Block height in pixels, this is intended to be accessed through
+	 * drm_format_info_block_height()
+	 */
+	u8 block_h[3];
 
 	/** @hsub: Horizontal chroma subsampling factor */
 	u8 hsub;
@@ -106,6 +157,12 @@ int drm_format_horz_chroma_subsampling(uint32_t format);
 int drm_format_vert_chroma_subsampling(uint32_t format);
 int drm_format_plane_width(int width, uint32_t format, int plane);
 int drm_format_plane_height(int height, uint32_t format, int plane);
+unsigned int drm_format_info_block_width(const struct drm_format_info *info,
+					 int plane);
+unsigned int drm_format_info_block_height(const struct drm_format_info *info,
+					  int plane);
+uint64_t drm_format_info_min_pitch(const struct drm_format_info *info,
+				   int plane, unsigned int buffer_width);
 const char *drm_get_format_name(uint32_t format, struct drm_format_name_buf *buf);
 
 #endif /* __DRM_FOURCC_H__ */