diff options
| -rw-r--r-- | Documentation/gpu/drm-kms.rst | 6 | ||||
| -rw-r--r-- | include/uapi/drm/drm_fourcc.h | 36 |
2 files changed, 42 insertions, 0 deletions
diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst index 5dee6b8a4c12..f8f5bf11a6ca 100644 --- a/Documentation/gpu/drm-kms.rst +++ b/Documentation/gpu/drm-kms.rst @@ -323,6 +323,12 @@ Frame Buffer Functions Reference DRM Format Handling =================== +.. kernel-doc:: include/uapi/drm/drm_fourcc.h + :doc: overview + +Format Functions Reference +-------------------------- + .. kernel-doc:: include/drm/drm_fourcc.h :internal: diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h index d43949b5bb3e..21c50b39596f 100644 --- a/include/uapi/drm/drm_fourcc.h +++ b/include/uapi/drm/drm_fourcc.h @@ -30,6 +30,42 @@ extern "C" { #endif +/** + * DOC: overview + * + * In the DRM subsystem, framebuffer pixel formats are described using the + * fourcc codes defined in `include/uapi/drm/drm_fourcc.h`. In addition to the + * fourcc code, a Format Modifier may optionally be provided, in order to + * further describe the buffer's format - for example tiling or compression. + * + * Format Modifiers + * ---------------- + * + * Format modifiers are used in conjunction with a fourcc code, forming a + * unique fourcc:modifier pair. This format:modifier pair must fully define the + * format and data layout of the buffer, and should be the only way to describe + * that particular buffer. + * + * Having multiple fourcc:modifier pairs which describe the same layout should + * be avoided, as such aliases run the risk of different drivers exposing + * different names for the same data format, forcing userspace to understand + * that they are aliases. + * + * Format modifiers may change any property of the buffer, including the number + * of planes and/or the required allocation size. Format modifiers are + * vendor-namespaced, and as such the relationship between a fourcc code and a + * modifier is specific to the modifer being used. For example, some modifiers + * may preserve meaning - such as number of planes - from the fourcc code, + * whereas others may not. + * + * Vendors should document their modifier usage in as much detail as + * possible, to ensure maximum compatibility across devices, drivers and + * applications. + * + * The authoritative list of format modifier codes is found in + * `include/uapi/drm/drm_fourcc.h` + */ + #define fourcc_code(a, b, c, d) ((__u32)(a) | ((__u32)(b) << 8) | \ ((__u32)(c) << 16) | ((__u32)(d) << 24)) |