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Message-ID: <68629132-b77a-bfbc-20f7-92a76cf24953@quicinc.com>
Date:   Fri, 30 Jun 2023 14:27:38 -0700
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Subject: Re: [PATCH RFC v4 2/7] drm: Introduce pixel_source DRM plane property
Content-Language: en-US
To:     Sebastian Wick <sebastian.wick@redhat.com>
CC:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Clark <robdclark@gmail.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        "Sean Paul" <sean@poorly.run>,
        Marijn Suijten <marijn.suijten@somainline.org>,
        <quic_abhinavk@quicinc.com>, <dri-devel@lists.freedesktop.org>,
        <linux-kernel@vger.kernel.org>, <ppaalanen@gmail.com>,
        <laurent.pinchart@ideasonboard.com>,
        <linux-arm-msm@vger.kernel.org>,
        <wayland-devel@lists.freedesktop.org>,
        <freedreno@lists.freedesktop.org>
References: <20230404-solid-fill-v4-0-f4ec0caa742d@quicinc.com>
 <20230404-solid-fill-v4-2-f4ec0caa742d@quicinc.com>
 <CA+hFU4zQFkbi8BjFdWDBDMPR7cC8UqJg0udu7MJYOFac1J8XsQ@mail.gmail.com>
From:   Jessica Zhang <quic_jesszhan@quicinc.com>
In-Reply-To: <CA+hFU4zQFkbi8BjFdWDBDMPR7cC8UqJg0udu7MJYOFac1J8XsQ@mail.gmail.com>
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On 6/30/2023 7:43 AM, Sebastian Wick wrote:
> On Fri, Jun 30, 2023 at 2:26 AM Jessica Zhang <quic_jesszhan@quicinc.com> wrote:
>>
>> Add support for pixel_source property to drm_plane and related
>> documentation.
>>
>> This enum property will allow user to specify a pixel source for the
>> plane. Possible pixel sources will be defined in the
>> drm_plane_pixel_source enum.
>>
>> The current possible pixel sources are DRM_PLANE_PIXEL_SOURCE_FB and
>> DRM_PLANE_PIXEL_SOURCE_COLOR. The default value is *_SOURCE_FB.
>>
>> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
>> ---
>>   drivers/gpu/drm/drm_atomic_state_helper.c |  1 +
>>   drivers/gpu/drm/drm_atomic_uapi.c         |  4 ++
>>   drivers/gpu/drm/drm_blend.c               | 81 +++++++++++++++++++++++++++++++
>>   include/drm/drm_blend.h                   |  2 +
>>   include/drm/drm_plane.h                   | 21 ++++++++
>>   5 files changed, 109 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
>> index fe14be2bd2b2..86fb876efbe6 100644
>> --- a/drivers/gpu/drm/drm_atomic_state_helper.c
>> +++ b/drivers/gpu/drm/drm_atomic_state_helper.c
>> @@ -252,6 +252,7 @@ void __drm_atomic_helper_plane_state_reset(struct drm_plane_state *plane_state,
>>
>>          plane_state->alpha = DRM_BLEND_ALPHA_OPAQUE;
>>          plane_state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
>> +       plane_state->pixel_source = DRM_PLANE_PIXEL_SOURCE_FB;
>>
>>          if (plane_state->solid_fill_blob) {
>>                  drm_property_blob_put(plane_state->solid_fill_blob);
>> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
>> index a28b4ee79444..6e59c21af66b 100644
>> --- a/drivers/gpu/drm/drm_atomic_uapi.c
>> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
>> @@ -596,6 +596,8 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
>>                  drm_property_blob_put(solid_fill);
>>
>>                  return ret;
>> +       } else if (property == plane->pixel_source_property) {
>> +               state->pixel_source = val;
>>          } else if (property == plane->alpha_property) {
>>                  state->alpha = val;
>>          } else if (property == plane->blend_mode_property) {
>> @@ -671,6 +673,8 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
>>          } else if (property == plane->solid_fill_property) {
>>                  *val = state->solid_fill_blob ?
>>                          state->solid_fill_blob->base.id : 0;
>> +       } else if (property == plane->pixel_source_property) {
>> +               *val = state->pixel_source;
>>          } else if (property == plane->alpha_property) {
>>                  *val = state->alpha;
>>          } else if (property == plane->blend_mode_property) {
>> diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
>> index 38c3c5d6453a..8c100a957ee2 100644
>> --- a/drivers/gpu/drm/drm_blend.c
>> +++ b/drivers/gpu/drm/drm_blend.c
>> @@ -189,6 +189,18 @@
>>    *     solid_fill is set up with drm_plane_create_solid_fill_property(). It
>>    *     contains pixel data that drivers can use to fill a plane.
>>    *
>> + * pixel_source:
>> + *     pixel_source is set up with drm_plane_create_pixel_source_property().
>> + *     It is used to toggle the source of pixel data for the plane.
>> + *
>> + *     Possible values:
>> + *
>> + *     "FB":
>> + *             Framebuffer source
>> + *
>> + *     "COLOR":
>> + *             solid_fill source
>> + *
>>    * Note that all the property extensions described here apply either to the
>>    * plane or the CRTC (e.g. for the background color, which currently is not
>>    * exposed and assumed to be black).
>> @@ -648,3 +660,72 @@ int drm_plane_create_solid_fill_property(struct drm_plane *plane)
>>          return 0;
>>   }
>>   EXPORT_SYMBOL(drm_plane_create_solid_fill_property);
>> +
>> +/**
>> + * drm_plane_create_pixel_source_property - create a new pixel source property
>> + * @plane: drm plane
>> + * @supported_sources: bitmask of supported pixel_sources for the driver (NOT
>> + *                     including DRM_PLANE_PIXEL_SOURCE_FB, as it will be supported
>> + *                     by default).
>> + *
>> + * This creates a new property describing the current source of pixel data for the
>> + * plane.
>> + *
>> + * The property is exposed to userspace as an enumeration property called
>> + * "pixel_source" and has the following enumeration values:
>> + *
>> + * "FB":
>> + *     Framebuffer pixel source
>> + *
>> + * "COLOR":
>> + *     Solid fill color pixel source
> 
> Can we add a "NONE" value?
> 
> I know it has been discussed earlier if we *need*  this and I don't
> think we do. I just think it would be better API design to disable
> planes this way than having to know that a framebuffer pixel source
> with a NULL framebuffer disables the plane. Obviously also keep the
> old behavior for backwards compatibility.

Hi Sebastian,

Sounds good.

So if pixel_source == NONE disables the planes, would that mean cases 
where pixel_source == COLOR && solid_fill_blob == NULL, the atomic 
commit should throw an error?

Thanks,

Jessica Zhang

> 
>> + *
>> + * Returns:
>> + * Zero on success, negative errno on failure.
>> + */
>> +int drm_plane_create_pixel_source_property(struct drm_plane *plane,
>> +                                          unsigned int supported_sources)
>> +{
>> +       struct drm_device *dev = plane->dev;
>> +       struct drm_property *prop;
>> +       const struct drm_prop_enum_list enum_list[] = {
>> +               { DRM_PLANE_PIXEL_SOURCE_FB, "FB" },
>> +               { DRM_PLANE_PIXEL_SOURCE_COLOR, "COLOR" },
>> +       };
>> +       unsigned int valid_source_mask = BIT(DRM_PLANE_PIXEL_SOURCE_FB) |
>> +                                      BIT(DRM_PLANE_PIXEL_SOURCE_COLOR);
>> +       int i;
>> +
>> +       /* FB is supported by default */
>> +       supported_sources |= BIT(DRM_PLANE_PIXEL_SOURCE_FB);
>> +
>> +       if (WARN_ON(supported_sources & ~valid_source_mask))
>> +               return -EINVAL;
>> +
>> +       prop = drm_property_create(dev, DRM_MODE_PROP_ENUM, "pixel_source",
>> +                       hweight32(supported_sources));
>> +
>> +       if (!prop)
>> +               return -ENOMEM;
>> +
>> +       for (i = 0; i < ARRAY_SIZE(enum_list); i++) {
>> +               int ret;
>> +
>> +               if (!(BIT(enum_list[i].type) & supported_sources))
>> +                       continue;
>> +
>> +               ret = drm_property_add_enum(prop, enum_list[i].type, enum_list[i].name);
>> +
>> +               if (ret) {
>> +                       drm_property_destroy(dev, prop);
>> +
>> +                       return ret;
>> +               }
>> +       }
>> +
>> +       drm_object_attach_property(&plane->base, prop, DRM_PLANE_PIXEL_SOURCE_FB);
>> +       plane->pixel_source_property = prop;
>> +
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL(drm_plane_create_pixel_source_property);
>> diff --git a/include/drm/drm_blend.h b/include/drm/drm_blend.h
>> index 0338a860b9c8..31af7cfa5b1b 100644
>> --- a/include/drm/drm_blend.h
>> +++ b/include/drm/drm_blend.h
>> @@ -59,4 +59,6 @@ int drm_atomic_normalize_zpos(struct drm_device *dev,
>>   int drm_plane_create_blend_mode_property(struct drm_plane *plane,
>>                                           unsigned int supported_modes);
>>   int drm_plane_create_solid_fill_property(struct drm_plane *plane);
>> +int drm_plane_create_pixel_source_property(struct drm_plane *plane,
>> +                                          unsigned int supported_sources);
>>   #endif
>> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
>> index f6ab313cb83e..73fb6cf8a5d9 100644
>> --- a/include/drm/drm_plane.h
>> +++ b/include/drm/drm_plane.h
>> @@ -59,6 +59,12 @@ struct drm_solid_fill {
>>          uint32_t b;
>>   };
>>
>> +enum drm_plane_pixel_source {
>> +       DRM_PLANE_PIXEL_SOURCE_FB,
>> +       DRM_PLANE_PIXEL_SOURCE_COLOR,
>> +       DRM_PLANE_PIXEL_SOURCE_MAX
>> +};
>> +
>>   /**
>>    * struct drm_plane_state - mutable plane state
>>    *
>> @@ -152,6 +158,14 @@ struct drm_plane_state {
>>           */
>>          struct drm_solid_fill solid_fill;
>>
>> +       /*
>> +        * @pixel_source:
>> +        *
>> +        * Source of pixel information for the plane. See
>> +        * drm_plane_create_pixel_source_property() for more details.
>> +        */
>> +       enum drm_plane_pixel_source pixel_source;
>> +
>>          /**
>>           * @alpha:
>>           * Opacity of the plane with 0 as completely transparent and 0xffff as
>> @@ -742,6 +756,13 @@ struct drm_plane {
>>           */
>>          struct drm_property *solid_fill_property;
>>
>> +       /*
>> +        * @pixel_source_property:
>> +        * Optional pixel_source property for this plane. See
>> +        * drm_plane_create_pixel_source_property().
>> +        */
>> +       struct drm_property *pixel_source_property;
>> +
>>          /**
>>           * @alpha_property:
>>           * Optional alpha property for this plane. See
>>
>> --
>> 2.41.0
>>
>