Hi Daniel, On Fri, Jun 26, 2020 at 04:07:43PM +0200, Daniel Vetter wrote: > On Fri, Jun 26, 2020 at 3:52 PM Brian Starkey <brian.starkey@xxxxxxx> wrote: > > > > In cases such as DRM_FORMAT_MOD_SAMSUNG_16_16_TILE, the modifier > > describes a generic pixel re-ordering which can be applicable to > > multiple vendors. > > > > Define an alias: DRM_FORMAT_MOD_GENERIC_16_16_TILE, which can be > > used to describe this layout in a vendor-neutral way, and add a > > comment about the expected usage of such "generic" modifiers. > > > > Signed-off-by: Brian Starkey <brian.starkey@xxxxxxx> > > --- > > > > This is based off a suggestion from Daniel here: > > https://lore.kernel.org/dri-devel/20200529115328.GC1630358@phenom.ffwll.local/ > > > > If there are future cases where a "generic" modifier is identified > > before merging with a specific vendor code, perhaps we could use > > `fourcc_mod_code(NONE, n)` or add a DRM_FORMAT_MOD_VENDOR_GENERIC. > > > > However, I also think we shouldn't try and "guess" what might be generic > > up-front and end up polluting the generic namespace. It seems fine to > > just alias vendor-specific definitions unless it's very clear-cut. > > I think the above two things would also be good additions to the comment. > > A totally different thing: I just noticed that we don't pull in all > the comments for modifiers. I think we could convert them to > kerneldoc, and then pull them into a separate section in drm-kms.rst. > Maybe even worth to pull out into a new drm-fourcc.rst document, since > these are officially shared with gl and vk standard extensions. Then > this new modifier's doc could simply point at teh existing one (and > the generated kerneldoc would make that a hyperlink for added > awesomeness). > > Aside from that makes sense to me, maybe just add it to your patch > series that will start making use of these. This is only supported by the GPU, so we wouldn't be using this on the Display side. Thanks, -Brian > -Daniel > > > > > I typed a version which was s/GENERIC/COMMON/, other suggestions > > welcome. > > > > Cheers, > > -Brian > > > > include/uapi/drm/drm_fourcc.h | 19 +++++++++++++++++++ > > 1 file changed, 19 insertions(+) > > > > diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h > > index 299f9ac4840b..ef78dc9c3fb0 100644 > > --- a/include/uapi/drm/drm_fourcc.h > > +++ b/include/uapi/drm/drm_fourcc.h > > @@ -345,8 +345,27 @@ extern "C" { > > * When adding a new token please document the layout with a code comment, > > * similar to the fourcc codes above. drm_fourcc.h is considered the > > * authoritative source for all of these. > > + * > > + * Generic modifier names: > > + * > > + * DRM_FORMAT_MOD_GENERIC_* definitions are used to provide vendor-neutral names > > + * for layouts which are common across multiple vendors. To preserve > > + * compatibility, in cases where a vendor-specific definition already exists and > > + * a generic name for it is desired, the common name is a purely symbolic alias > > + * and must use the same numerical value as the original definition. > > + * > > + * Note that generic names should only be used for modifiers which describe > > + * generic layouts (such as pixel re-ordering), which may have > > + * independently-developed support across multiple vendors. > > + * > > + * Generic names should not be used for cases where multiple hardware vendors > > + * have implementations of the same standardised compression scheme (such as > > + * AFBC). In those cases, all implementations should use the same format > > + * modifier(s), reflecting the vendor of the standard. > > */ > > > > +#define DRM_FORMAT_MOD_GENERIC_16_16_TILE DRM_FORMAT_MOD_SAMSUNG_16_16_TILE > > + > > /* > > * Invalid Modifier > > * > > -- > > 2.17.1 > > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
