[PATCH] RFC: drm/drm_plane: Expose the plane capability and interoperability

Wed Jul 31 08:33:45 UTC 2024

On Tue, 30 Jul 2024 at 07:07, Murthy, Arun R <arun.r.murthy at intel.com> wrote:
>
> > -----Original Message-----
> > From: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> > Sent: Tuesday, July 30, 2024 4:21 AM
> > To: Murthy, Arun R <arun.r.murthy at intel.com>
> > Cc: dri-devel at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
> > Subject: Re: [PATCH] RFC: drm/drm_plane: Expose the plane capability and
> > interoperability

Please fix your email client.

> >
> > On Mon, Jul 29, 2024 at 04:59:14AM GMT, Murthy, Arun R wrote:
> > > Gentle Reminder!
> > > Any comments?
> >
> > First of all, the format is underdocumented. Second, there is a usual
> > requirement for new uAPI: please provide a pointer to IGT patch and to the
> > userspace utilising the property.
> There are some discussions on using this in UMD. https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29618#note_2487123

It should be a MR rather than "some discussion". And IGT patchset too, please.

Regarding the patch itself. It is completely underdocumented. There is
no way for me to understand which of these caps should e.g. be set for
the drm/msm planes.

>
> Thanks and Regards,
> Arun R Murthy
> --------------------
> >
> > >
> > > Thanks and Regards,
> > > Arun R Murthy
> > > --------------------
> > >
> > > > -----Original Message-----
> > > > From: Murthy, Arun R <arun.r.murthy at intel.com>
> > > > Sent: Tuesday, July 9, 2024 1:17 PM
> > > > To: dri-devel at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
> > > > Cc: Murthy, Arun R <arun.r.murthy at intel.com>
> > > > Subject: [PATCH] RFC: drm/drm_plane: Expose the plane capability and
> > > > interoperability
> > > >
> > > > Each plane has its own capability or interoperability based on the
> > > > harware restrictions. If this is exposed to the user, then user can
> > > > read it once on boot and store this. Later can be used as a lookup
> > > > table to check a corresponding capability is supported by plane then
> > > > only go ahead with the framebuffer creation/calling atomic_ioctl.
> > > >
> > > > For Ex: There are few restiction as to async flip doesnt support all
> > > > the formats/modifiers. Similar restrictions on scaling. With the
> > > > availabililty of this info to user, failures in atomic_check can be
> > > > avoided as these are more the hardware capabilities.
> > > >
> > > > There are two options on how this can be acheived.
> > > > Option 1:
> > > >
> > > > Add a new element to struct drm_mode_get_plane that holds the addr
> > > > to the array of a new struct. This new struct consists of the
> > > > formats supported and the corresponding plane capabilities.
> > > >
> > > > Option 2:
> > > >
> > > > These can be exposed to user as a plane property so that the user
> > > > can get to know the limitation ahead and avoid failures in atomic_check.
> > > >
> > > > Usually atomic_get_property is controlled over the state struct for
> > > > the parameters/elements that can change. But here these capabilities
> > > > or the interoperabilities are rather hardware restrictions and wont change
> > over flips.
> > > > Hence having as a plane_property may not make much sense.
> > > > On the other hand, Option 1 include changes in the uapi struct
> > > > drm_mode_get_plane. Shouldnt have impact on backward compatibility,
> > > > but if userspace has some implementation so as to check the size of
> > > > the struct, then it might a challenge.
> > > >
> > > > Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
> > > > ---
> > > >  drivers/gpu/drm/drm_atomic_uapi.c |  3 +++
> > > >  include/drm/drm_plane.h           |  8 ++++++++
> > > >  include/uapi/drm/drm_mode.h       | 20 ++++++++++++++++++++
> > > >  3 files changed, 31 insertions(+)
> > > >
> > > > =============Option 2========================
> > > >
> > > > diff --git a/drivers/gpu/drm/drm_atomic_uapi.c
> > > > b/drivers/gpu/drm/drm_atomic_uapi.c
> > > > index 22bbb2d83e30..b46177d5fc8c 100644
> > > > --- a/drivers/gpu/drm/drm_atomic_uapi.c
> > > > +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> > > > @@ -631,6 +631,9 @@ drm_atomic_plane_get_property(struct drm_plane
> > > > *plane,
> > > >           *val = state->hotspot_x;
> > > >   } else if (property == plane->hotspot_y_property) {
> > > >           *val = state->hotspot_y;
> > > > + } else if (property == config->prop_plane_caps) {
> > > > +         *val = (state->plane_caps) ?
> > > > +                 state->plane_caps->base.id : 0;
> > > >   } else {
> > > >           drm_dbg_atomic(dev,
> > > >                          "[PLANE:%d:%s] unknown property
> > [PROP:%d:%s]\n", diff
> > > > --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h index
> > > > dd718c62ac31..dfe931677d0a 100644
> > > > --- a/include/drm/drm_plane.h
> > > > +++ b/include/drm/drm_plane.h
> > > > @@ -260,6 +260,14 @@ struct drm_plane_state {
> > > >    * flow.
> > > >    */
> > > >   bool color_mgmt_changed : 1;
> > > > +
> > > > + /**
> > > > +  * @plane_caps:
> > > > +  *
> > > > +  * Blob representing plane capcabilites and interoperability.
> > > > +  * This element is a pointer to the array of struct drm_format_blob.
> > > > +  */
> > > > + struct drm_property_blob *plane_caps;
> > > >  };
> > > >
> > > >  static inline struct drm_rect
> > > >
> > > > =============Option 1========================
> > > >
> > > > diff --git a/include/uapi/drm/drm_mode.h
> > > > b/include/uapi/drm/drm_mode.h index d390011b89b4..0b5c1b65ef63
> > > > 100644
> > > > --- a/include/uapi/drm/drm_mode.h
> > > > +++ b/include/uapi/drm/drm_mode.h
> > > > @@ -312,6 +312,20 @@ struct drm_mode_set_plane {
> > > >   __u32 src_w;
> > > >  };
> > > >
> > > > +#define DRM_FORMAT_PLANE_CAP_LINEAR_TILE BIT(0)
> > > > +#define DRM_FORMAT_PLANE_CAP_X_TILE              BIT(1)
> > > > +#define DRM_FORMAT_PLANE_CAP_Y_TILE              BIT(2)
> > > > +#define DRM_FORMAT_PLANE_CAP_Yf_TILE             BIT(3)
> > > > +#define DRM_FORMAT_PLANE_CAP_ASYNC_FLIP          BIT(4)
> > > > +#define DRM_FORMAT_PLANE_CAP_FBC         BIT(5)
> > > > +#define DRM_FORMAT_PLANE_CAP_RC                  BIT(6)
> > > > +
> > > > +struct drm_format_blob {
> > > > + __u64 modifier;
> > > > + __u32 plane_caps;
> > > > +
> > > > +};
> > > > +
> > > >  /**
> > > >   * struct drm_mode_get_plane - Get plane metadata.
> > > >   *
> > > > @@ -355,6 +369,12 @@ struct drm_mode_get_plane {
> > > >    * supported by the plane. These formats do not require modifiers.
> > > >    */
> > > >   __u64 format_type_ptr;
> > > > + /**
> > > > +  * @ format_blob_ptr: Pointer to the array of struct drm_format_blob.
> > > > +  * Specify the plane capabilites/restrictions w.r.t tiling/sync-async
> > > > +  * flips etc
> > > > +  */
> > > > + __u64 format_blob_ptr;
> > > >  };
> > > >
> > > >  struct drm_mode_get_plane_res {
> > > > --
> > > > 2.25.1
> > >
> >
> > --
> > With best wishes
> > Dmitry

-- 
With best wishes
Dmitry