On Fri, Jun 26, 2020 at 4:16 PM Brian Starkey <brian.starkey@xxxxxxx> wrote: > > 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. I mean the patch to add the NV15 fource, it mentions "suitable for 16 by 16 tile layout", would be nice to just put the generic modifier in that comment. -Daniel > > 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 -- 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
