On Wed, May 09, 2018 at 10:08:16AM +0200, Daniel Vetter wrote:
> On Tue, May 08, 2018 at 06:34:36PM +0800, Lowry Li wrote:
> > Pixel blend modes represent the alpha blending equation
> > selection, describing how the pixels from the current
> > plane are composited with the background.
> >
> > Add a pixel_blend_mode to drm_plane_state and a
> > blend_mode_property to drm_plane, and related support
> > functions.
> >
> > Defines three blend modes in drm_blend.h.
> >
> > Signed-off-by: Lowry Li <lowry.li@xxxxxxx>
>
> Some suggestions for the kerneldoc below. lgtm otherwise (but needs the
> driver implementation + userspace support before we can merge).
> -Daniel
Thanks for the review comments.
OK. Driver implementation and userspace support will be committed in
other patchsets.
> > ---
> > drivers/gpu/drm/drm_atomic.c | 4 ++
> > drivers/gpu/drm/drm_atomic_helper.c | 1 +
> > drivers/gpu/drm/drm_blend.c | 95 +++++++++++++++++++++++++++++++++++++
> > include/drm/drm_blend.h | 6 +++
> > include/drm/drm_plane.h | 7 +++
> > 5 files changed, 113 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index a567310..0bb6de1 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -764,6 +764,8 @@ int drm_atomic_plane_set_property(struct drm_plane *plane,
> > state->src_w = val;
> > } else if (property == config->prop_src_h) {
> > state->src_h = val;
> > + } else if (property == plane->blend_mode_property) {
> > + state->pixel_blend_mode = val;
> > } else if (property == plane->rotation_property) {
> > if (!is_power_of_2(val & DRM_ROTATE_MASK))
> > return -EINVAL;
> > @@ -826,6 +828,8 @@ int drm_atomic_plane_set_property(struct drm_plane *plane,
> > *val = state->src_w;
> > } else if (property == config->prop_src_h) {
> > *val = state->src_h;
> > + } else if (property == plane->blend_mode_property) {
> > + *val = state->pixel_blend_mode;
> > } else if (property == plane->rotation_property) {
> > *val = state->rotation;
> > } else if (property == plane->zpos_property) {
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 01d936b..e4377fd 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -3133,6 +3133,7 @@ void drm_atomic_helper_plane_reset(struct drm_plane *plane)
> > if (plane->state) {
> > plane->state->plane = plane;
> > plane->state->rotation = DRM_ROTATE_0;
> > + plane->state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
> > }
> > }
> > EXPORT_SYMBOL(drm_atomic_helper_plane_reset);
> > diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
> > index 665aafc..bb938de 100644
> > --- a/drivers/gpu/drm/drm_blend.c
> > +++ b/drivers/gpu/drm/drm_blend.c
> > @@ -98,6 +98,12 @@
> > * planes. Without this property the primary plane is always below the cursor
> > * plane, and ordering between all other planes is undefined.
> > *
> > + * pixel blend mode:
> > + * Pixel blend mode is set up with drm_plane_create_blend_mode_property().
> > + * It adds a blend mode for alpha blending equation selection, describing
> > + * how the pixels from the current plane are composited with the
> > + * background.
>
> I think a link here to drm_plane_create_blend_mode_property() for the
> blending equations would be really good.
About the details of blending equations, as your comments below, we
will move them here. And drm_plane_create_blend_mode_property()
already has a link which can take the reader to the function easily.
> > + *
> > * 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).
> > @@ -405,3 +411,92 @@ int drm_atomic_normalize_zpos(struct drm_device *dev,
> > return 0;
> > }
> > EXPORT_SYMBOL(drm_atomic_normalize_zpos);
> > +
> > +/**
> > + * drm_plane_create_blend_mode_property - create a new blend mode property
> > + * @plane: drm plane
> > + * @supported_modes: bitmask of supported modes, must include
> > + * BIT(DRM_MODE_BLEND_PREMULTI)
> > + *
> > + * This creates a new property describing the blend mode.
> > + *
> > + * The property exposed to userspace is an enumeration property (see
> > + * drm_property_create_enum()) called "pixel blend mode" and has the
> > + * following enumeration values:
> > + *
> > + * DRM_MODE_BLEND_PIXEL_NONE: Blend formula that ignores the pixel alpha.
>
> Please don't enumerate the #defines, but instead the string values (i.e.
> "None" here). Enum properties are supposed to be identified with their
> string values (but in practice we probably can't ever change the
> corresponding numeric values).
Ok, will delete the "DRM_MODE_BLEND_PIXEL_NONE" bits.
> > + * "None"
> > + * out.rgb = plane.alpha * pixel.rgb + (1 - plane.alpha) * bg.rgb
>
> Would be good to define what the different variables here mean.
>
> Also I think putting the blending equation into the DOC comment would be
> good, so that when we do further blending properties we can have one
> overall big picture for how this works. Instead of everything spread
> around. Also maybe use fg.* instead of pixel.* and plane_alpha instead of
> plane.alpha (to make it clear it's just one value).
Will move the blending equation to the DOC comment.
Ok, will use fg.* instead of pixel.* and plane_alpha instead of
plane.alpha.
> > + *
> > + * DRM_MODE_BLEND_PREMULTI: Blend formula that assumes the pixel color values
> > + * have been already pre-multiplied with the alpha
> > + * channel values.
> > + * "Pre-multiplied"
> > + * out.rgb = plane.alpha * pixel.rgb +
> > + * (1 - (plane.alpha * pixel.alpha)) * bg.rgb
> > + *
> > + * DRM_MODE_BLEND_COVERAGE: Blend formula that assumes the pixel color values
> > + * have not been pre-multiplied and will do so when
> > + * blending them to the background color values.
> > + * "Coverage"
> > + * out.rgb = plane.alpha * pixel.alpha * pixel.rgb +
> > + * (1 - (plane.alpha * pixel.alpha)) * bg.rgb
> > + *
> > + * This property has no effect on formats with no pixel alpha, as pixel.alpha
> > + * is assumed to be 1.0. If the plane does not expose the "alpha" property, then
> > + * plane.alpha is assumed to be 1.0, otherwise, it is the value of the "alpha"
> > + * property.
> > + *
> > + * RETURNS:
> > + * Zero for success or -errno
> > + */
> > +int drm_plane_create_blend_mode_property(struct drm_plane *plane,
> > + unsigned int supported_modes)
> > +{
> > + struct drm_device *dev = plane->dev;
> > + struct drm_property *prop;
> > + static const struct drm_prop_enum_list props[] = {
> > + { DRM_MODE_BLEND_PIXEL_NONE, "None" },
> > + { DRM_MODE_BLEND_PREMULTI, "Pre-multiplied" },
> > + { DRM_MODE_BLEND_COVERAGE, "Coverage" },
> > + };
> > + unsigned int valid_mode_mask = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
> > + BIT(DRM_MODE_BLEND_PREMULTI) |
> > + BIT(DRM_MODE_BLEND_COVERAGE);
> > + int i, j = 0;
> > +
> > + if (WARN_ON((supported_modes & ~valid_mode_mask) ||
> > + ((supported_modes & BIT(DRM_MODE_BLEND_PREMULTI)) == 0)))
> > + return -EINVAL;
> > +
> > + prop = drm_property_create(dev, DRM_MODE_PROP_ENUM,
> > + "pixel blend mode",
> > + hweight32(supported_modes));
> > + if (!prop)
> > + return -ENOMEM;
> > +
> > + for (i = 0; i < ARRAY_SIZE(props); i++) {
> > + int ret;
> > +
> > + if (!(BIT(props[i].type) & supported_modes))
> > + continue;
> > +
> > + ret = drm_property_add_enum(prop, j++, props[i].type,
> > + props[i].name);
> > +
> > + if (ret) {
> > + drm_property_destroy(dev, prop);
> > +
> > + return ret;
> > + }
> > + }
> > +
> > + drm_object_attach_property(&plane->base, prop, DRM_MODE_BLEND_PREMULTI);
> > + plane->blend_mode_property = prop;
> > +
> > + if (plane->state)
> > + plane->state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(drm_plane_create_blend_mode_property);
> > diff --git a/include/drm/drm_blend.h b/include/drm/drm_blend.h
> > index 13221cf..6bf95a4 100644
> > --- a/include/drm/drm_blend.h
> > +++ b/include/drm/drm_blend.h
> > @@ -26,6 +26,10 @@
> > #include <linux/list.h>
> > #include <linux/ctype.h>
> >
> > +#define DRM_MODE_BLEND_PIXEL_NONE 0
> > +#define DRM_MODE_BLEND_PREMULTI 1
> > +#define DRM_MODE_BLEND_COVERAGE 2
> > +
> > struct drm_device;
> > struct drm_atomic_state;
> >
> > @@ -65,4 +69,6 @@ int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
> > unsigned int zpos);
> > int drm_atomic_normalize_zpos(struct drm_device *dev,
> > struct drm_atomic_state *state);
> > +int drm_plane_create_blend_mode_property(struct drm_plane *plane,
> > + unsigned int supported_modes);
> > #endif
> > diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> > index 20867b4..f9cbfee 100644
> > --- a/include/drm/drm_plane.h
> > +++ b/include/drm/drm_plane.h
> > @@ -41,6 +41,8 @@
> > * plane (in 16.16)
> > * @src_w: width of visible portion of plane (in 16.16)
> > * @src_h: height of visible portion of plane (in 16.16)
> > + * @pixel_blend_mode: how the plane's framebuffer alpha channel is used when
> > + * blending with the background colour.
> > * @rotation: rotation of the plane
> > * @zpos: priority of the given plane on crtc (optional)
> > * Note that multiple active planes on the same crtc can have an identical
> > @@ -104,6 +106,9 @@ struct drm_plane_state {
> > uint32_t src_x, src_y;
> > uint32_t src_h, src_w;
> >
> > + /* Plane pixel blend mode */
>
> Please use in-line struct member comments when you feel like you need a
> comment here too. Yes we should probably change the other comments too.
> Also would be good to again point at
> drm_plane_create_zpos_immutable_property() and related stuff.
We've given the detail description of it on the comments of
drm_plane_state. So we can remove the comment here.
> > + uint16_t pixel_blend_mode;
> > +
> > /* Plane rotation */
> > unsigned int rotation;
> >
> > @@ -459,6 +464,7 @@ enum drm_plane_type {
> > * @state: current atomic state for this plane
> > * @zpos_property: zpos property for this plane
> > * @rotation_property: rotation property for this plane
> > + * @blend_mode_property: blend mode property for this plane
> > * @helper_private: mid-layer private data
> > */
> > struct drm_plane {
> > @@ -506,6 +512,7 @@ struct drm_plane {
> >
> > struct drm_property *zpos_property;
> > struct drm_property *rotation_property;
> > + struct drm_property *blend_mode_property;
> > };
> >
> > #define obj_to_plane(x) container_of(x, struct drm_plane, base)
> > --
> > 1.9.1
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
--
Regards,
Lowry
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