[PATCH v4] linux-dmabuf: clarify DRM_FORMAT_MOD_INVALID

[Pekka Paalanen]

On Wed, 24 Apr 2019 10:07:47 -0700
Chia-I Wu <olvaffe at gmail.com> wrote:

> Hi,
> 
> Can you commit this patch for me, if all looks good?

Hi Chia-I,

I was almost already pushing this, but Daniel said he wants to have
a good look first.


Thanks,
pq

> On Wed, Apr 17, 2019 at 9:41 AM Chia-I Wu <olvaffe at gmail.com> wrote:
> >
> > I hope this captures the discussion: clarify DRM_FORMAT_MOD_INVALID and a note
> >
> > On Wed, Apr 17, 2019 at 9:40 AM Chia-I Wu <olvaffe at gmail.com> wrote:  
> > >
> > > DRM_FORMAT_MOD_INVALID means to derive the modifier from the dmabuf.
> > > It provides legacy support and makes it easier to replace wl_drm.
> > >
> > > v3: DRM_FORMAT_MOD_INVALID must be advertised to be supported (which
> > >     requires a version bump)
> > > v4: no version bump, but a note for now
> > >
> > > Signed-off-by: Chia-I Wu <olvaffe at gmail.com>
> > > Reviewed-by: Pekka Paalanen <pekka.paalanen at collabora.com>
> > > Reviewed-by: Simon Ser <contact at emersion.fr>
> > > ---
> > >  .../linux-dmabuf/linux-dmabuf-unstable-v1.xml    | 16 +++++++++++++++-
> > >  1 file changed, 15 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml b/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> > > index 154afe2..b43e81c 100644
> > > --- a/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> > > +++ b/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> > > @@ -28,6 +28,7 @@
> > >      <description summary="factory for creating dmabuf-based wl_buffers">
> > >        Following the interfaces from:
> > >        https://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_import.txt
> > > +      https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_image_dma_buf_import_modifiers.txt
> > >        and the Linux DRM sub-system's AddFb2 ioctl.
> > >
> > >        This interface offers ways to create generic dmabuf-based
> > > @@ -129,8 +130,16 @@
> > >          binds to this interface. A roundtrip after binding guarantees that
> > >          the client has received all supported format-modifier pairs.
> > >
> > > +        For legacy support, DRM_FORMAT_MOD_INVALID (that is, modifier_hi ==
> > > +        0x00ffffff and modifier_lo == 0xffffffff) is allowed in this event.
> > > +        It indicates that the server can support the format with an implicit
> > > +        modifier. When a plane has DRM_FORMAT_MOD_INVALID as its modifier, it
> > > +        is as if no explicit modifier is specified. The effective modifier
> > > +        will be derived from the dmabuf.
> > > +
> > >          For the definition of the format and modifier codes, see the
> > > -        zwp_linux_buffer_params_v1::create request.
> > > +        zwp_linux_buffer_params_v1::create and zwp_linux_buffer_params_v1::add
> > > +        requests.
> > >        </description>
> > >        <arg name="format" type="uint" summary="DRM_FORMAT code"/>
> > >        <arg name="modifier_hi" type="uint"
> > > @@ -197,6 +206,11 @@
> > >          compression, etc. driver-specific modifications to the base format
> > >          defined by the DRM fourcc code.
> > >
> > > +        Warning: It should be an error if the format/modifier pair was not
> > > +        advertised with the modifier event. This is not enforced yet because
> > > +        some implementations always accept DRM_FORMAT_MOD_INVALID. Also
> > > +        version 2 of this protocol does not have the modifier event.
> > > +
> > >          This request raises the PLANE_IDX error if plane_idx is too large.
> > >          The error PLANE_SET is raised if attempting to set a plane that
> > >          was already set.
> > > --
> > > 2.21.0.392.gf8f6787159e-goog
> > >  
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