<div dir="ltr">The comment explains the problem with DRM_FORMAT_MOD_LINEAR. Signed-off-by: Marek Olšák <<a href="mailto:marek.olsak@amd.com">marek.olsak@amd.com</a>> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h index 78abd819fd62e..8ec4163429014 100644 --- a/include/uapi/drm/drm_fourcc.h +++ b/include/uapi/drm/drm_fourcc.h @@ -484,9 +484,27 @@ extern "C" { * modifier (e.g. not setting DRM_MODE_FB_MODIFIERS in the DRM_ADDFB2 ioctl), * which tells the driver to also take driver-internal information into account * and so might actually result in a tiled framebuffer. + * + * WARNING: + * There are drivers out there that expose DRM_FORMAT_MOD_LINEAR, but only + * support a certain pitch alignment and can't import images with this modifier + * if the pitch alignment isn't exactly the one supported. They can however + * allocate images with this modifier and other drivers can import them only + * if they support the same pitch alignment. Thus, DRM_FORMAT_MOD_LINEAR is + * fundamentically incompatible across devices and is the only modifier that + * has a chance of not working. The PITCH_ALIGN modifiers should be used + * instead. */ #define DRM_FORMAT_MOD_LINEAR fourcc_mod_code(NONE, 0) +/* Linear layout modifiers with an explicit pitch alignment in bytes. + * Exposing this modifier requires that the pitch alignment is exactly + * the number in the definition. + */ +#define DRM_FORMAT_MOD_LINEAR_PITCH_ALIGN_64B fourcc_mod_code(NONE, 1) </div>