On Tue, Apr 09, 2024 at 12:04:07PM +0200, Louis Chauvet wrote: > /** > * struct drm_format_info - information about a DRM format > + * > + * A drm_format_info describes how planes and pixels are stored in memory. > + * > + * Some format like YUV can have multiple planes, counted in @num_planes. It > + * means that a full pixel can be stored in multiple non-continuous buffers. > + * For example, NV12 is a YUV format using two planes: one for the Y values and > + * one for the UV values. > + * > + * On each plane, the "pixel" unit can be different in case of subsampling. For > + * example with the NV12 format, a pixel in the UV plane is used for four pixels > + * in the Y plane. > + * The fields @hsub and @vsub are the relation between the size of the main > + * plane and the size of the subsampled planes in pixels: > + * plane[0] width = hsub * plane[1] width > + * plane[0] height = vsub * plane[1] height > + * > + * In some formats, pixels are not independent in memory. It can be a packed > + * representation to store more pixels per byte (for example P030 uses 4 bytes > + * for three 10 bit pixels). It can also be used to represent tiled formats, > + * where a continuous buffer in memory can represent a rectangle of pixels (for > + * example, in DRM_FORMAT_Y0L0, a buffer of 8 bytes represents a 2x2 pixel > + * region of the picture). > + * The field @char_per_block is the size of a block on a specific plane, in > + * bytes. > + * The fields @block_w and @block_h are the size of a block in pixels. > + * > + * The older format representation (which only uses @cpp, kept for historical > + * reasons because there are a lot of places in drivers where it's used) is > + * assuming that a block is always 1x1 pixel. > + * > + * To keep the compatibility with older format representations and treat block > + * and non-block formats in the same way one should use: > + * - @char_per_block to access the size of a block on a specific plane, in > + * bytes. > + * - drm_format_info_block_width() to access the width of a block of a > + * specific plane, in pixels. > + * - drm_format_info_block_height() to access the height of a block of a > + * specific plane, in pixels. > */ > struct drm_format_info { > /** @format: 4CC format identifier (DRM_FORMAT_*) */ > @@ -97,13 +135,6 @@ struct drm_format_info { > * 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 > Sphinx reports htmldocs warnings: Documentation/gpu/drm-kms:357: ./include/drm/drm_fourcc.h:74: ERROR: Unexpected indentation. Documentation/gpu/drm-kms:357: ./include/drm/drm_fourcc.h:83: ERROR: Unexpected indentation. Documentation/gpu/drm-kms:357: ./include/drm/drm_fourcc.h:93: ERROR: Unexpected indentation. Documentation/gpu/drm-kms:357: ./include/drm/drm_fourcc.h:94: WARNING: Bullet list ends without a blank line; unexpected unindent. I have to fix up the lists: ---- >8 ---- diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h index 66cc30e28f794a..10ee74fa46d21e 100644 --- a/include/drm/drm_fourcc.h +++ b/include/drm/drm_fourcc.h @@ -71,8 +71,9 @@ struct drm_mode_fb_cmd2; * in the Y plane. * The fields @hsub and @vsub are the relation between the size of the main * plane and the size of the subsampled planes in pixels: - * plane[0] width = hsub * plane[1] width - * plane[0] height = vsub * plane[1] height + * + * - plane[0] width = hsub * plane[1] width + * - plane[0] height = vsub * plane[1] height * * In some formats, pixels are not independent in memory. It can be a packed * representation to store more pixels per byte (for example P030 uses 4 bytes @@ -80,9 +81,10 @@ struct drm_mode_fb_cmd2; * where a continuous buffer in memory can represent a rectangle of pixels (for * example, in DRM_FORMAT_Y0L0, a buffer of 8 bytes represents a 2x2 pixel * region of the picture). - * The field @char_per_block is the size of a block on a specific plane, in - * bytes. - * The fields @block_w and @block_h are the size of a block in pixels. + * + * - The field @char_per_block is the size of a block on a specific plane, + * in bytes. + * - The fields @block_w and @block_h are the size of a block in pixels. * * The older format representation (which only uses @cpp, kept for historical * reasons because there are a lot of places in drivers where it's used) is @@ -90,12 +92,13 @@ struct drm_mode_fb_cmd2; * * To keep the compatibility with older format representations and treat block * and non-block formats in the same way one should use: + * * - @char_per_block to access the size of a block on a specific plane, in - * bytes. + * bytes. * - drm_format_info_block_width() to access the width of a block of a - * specific plane, in pixels. + * specific plane, in pixels. * - drm_format_info_block_height() to access the height of a block of a - * specific plane, in pixels. + * specific plane, in pixels. */ struct drm_format_info { /** @format: 4CC format identifier (DRM_FORMAT_*) */ Thanks. -- An old man doll... just what I always wanted! - Clara
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