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

[Marek Olšák]

git send-email (or rather the way it sends email) has been banned by gmail
due to being considered unsecure. I don't plan to find a way to make it
work and I don't plan to use a different email provider. It doesn't matter
because I'll be the committer of this patch in our amd-staging-drm-next
branch.

Let's talk about the concept and brokenness of DRM_FORMAT_MOD_LINEAR, not
send-email.

Marek

On Sun, Dec 15, 2024 at 9:08 PM Joshua Ashton <joshua at froggi.es> wrote:

> Not really for my benefit, more that it's the proper thing to do if you
> want anyone to apply your patch.
>
> You should really just be using git send-email.
>
> On 12/15/24 11:57 PM, Marek Olšák wrote:
> > Only for you: Attached.
> >
> > Marek
> >
> > On Sun, Dec 15, 2024 at 6:37 PM Joshua Ashton <joshua at froggi.es
> > <mailto:joshua at froggi.es>> wrote:
> >
> >     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>
> >      > <mailto: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>
> >      >     <mailto: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 🐸✨
> >
>
> - Joshie 🐸✨
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/amd-gfx/attachments/20241216/de8e2243/attachment.htm>