[PATCH] drm/fourcc: add LINEAR modifiers with an exact pitch alignment

[Joshua Ashton]

You should just re-send the whole patch, probably.

On 12/15/24 8:54 PM, Marek Olšák wrote:
> Missed 2 lines from the diff:
> 
> +#define DRM_FORMAT_MOD_LINEAR_PITCH_ALIGN_128B fourcc_mod_code(NONE, 2)
> +#define DRM_FORMAT_MOD_LINEAR_PITCH_ALIGN_256B fourcc_mod_code(NONE, 3)
> 
> Marek
> 
> On Sun, Dec 15, 2024 at 3:53 PM Marek Olšák <maraeo at gmail.com 
> <mailto:maraeo at gmail.com>> wrote:
> 
>     The comment explains the problem with DRM_FORMAT_MOD_LINEAR.
> 
>     Signed-off-by: Marek Olšák <marek.olsak at amd.com
>     <mailto:marek.olsak at amd.com>>
> 
>     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)
> 

- Joshie 🐸✨