Re: [PATCH] drm/doc: Document that modifiers are always required for fb

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Sep 17, 2020 at 07:24:58PM +0200, Bas Nieuwenhuizen wrote:
> Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
> 
> On Thu, Sep 17, 2020 at 6:48 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > Even for legacy userspace, since otherwise GETFB2 is broken and if you
> > switch between modifier-less and modifier-aware compositors, smooth
> > transitions break.
> >
> > Also it's just best practice to make sure modifiers are invariant for
> > a given drm_fb, and that a modifier-aware kms drivers only has one
> > place to store them, ignoring any old implicit bo flags or whatever
> > else might float around.
> >
> > Motivated by some irc discussion with Bas about amdgpu modifier
> > support.
> >
> > Acked-by: Simon Ser <contact@emersion.fr>
> > Acked-by: Daniel Stone <daniels@collabora.com>
> > Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
> > Fixes: 455e00f1412f ("drm: Add getfb2 ioctl")
> > Cc: Daniel Stone <daniels@collabora.com>
> > Cc: Juston Li <juston.li@intel.com>
> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
> > Cc: Marek Olšák <maraeo@gmail.com>
> > Cc: "Wentland, Harry" <harry.wentland@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

Pushed to drm-misc-next, thanks for all the feedback.
-Daniel

> > ---
> > Sending this out again to double-check there's no objections or concerns.
> > From what I understand looking at the code the latest modifier patches for
> > amdgpu follow this now.
> >
> > Cheers, Daniel
> > ---
> >  include/drm/drm_mode_config.h | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> > index a18f73eb3cf6..5ffbb4ed5b35 100644
> > --- a/include/drm/drm_mode_config.h
> > +++ b/include/drm/drm_mode_config.h
> > @@ -58,6 +58,12 @@ struct drm_mode_config_funcs {
> >          * actual modifier used if the request doesn't have it specified,
> >          * ie. when (@mode_cmd->flags & DRM_MODE_FB_MODIFIERS) == 0.
> >          *
> > +        * IMPORTANT: These implied modifiers for legacy userspace must be
> > +        * stored in struct &drm_framebuffer, including all relevant metadata
> > +        * like &drm_framebuffer.pitches and &drm_framebuffer.offsets if the
> > +        * modifier enables additional planes beyond the fourcc pixel format
> > +        * code. This is required by the GETFB2 ioctl.
> > +        *
> >          * If the parameters are deemed valid and the backing storage objects in
> >          * the underlying memory manager all exist, then the driver allocates
> >          * a new &drm_framebuffer structure, subclassed to contain
> > @@ -915,6 +921,13 @@ struct drm_mode_config {
> >          * @allow_fb_modifiers:
> >          *
> >          * Whether the driver supports fb modifiers in the ADDFB2.1 ioctl call.
> > +        *
> > +        * IMPORTANT:
> > +        *
> > +        * If this is set the driver must fill out the full implicit modifier
> > +        * information in their &drm_mode_config_funcs.fb_create hook for legacy
> > +        * userspace which does not set modifiers. Otherwise the GETFB2 ioctl is
> > +        * broken for modifier aware userspace.
> >          */
> >         bool allow_fb_modifiers;
> >
> > --
> > 2.28.0
> >

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel