On Thu, Feb 22, 2018 at 04:54:08AM +0100, Stefan Schake wrote: > Android assumes an implicit black background layer is always present > behind all layers it specifies for composition. drm_hwcomposer currently > punts responsibility for this to the kernel/DRM platform and puts layers > with per-pixel alpha content on the primary plane when requested. > > On some platforms (e.g. VC4) a background color fill has a cycle cost for > the hardware composer and is not enabled by default. Instead, userland can > request a background color through a CRTC property. Use this property to > specify the implicit black background Android expects. > > Signed-off-by: Stefan Schake <stschake@xxxxxxxxx> > --- > Kernel changes for this (background_color) are available here: > > https://github.com/stschake/linux/commits/background-upstream > > Sending as RFC because I'm not entirely clear on whose responsibility > this should be, on most DRM drivers it seems to be implicit. I think > a case could also be made that VC4 should not accept alpha formats on > the lowest layer or enable background color fill when given one anyway. > On the other hand, userland control over background color seems desirable > regardless and is a feature of multiple hardware composers (i915, vc4, omap). I see you've already typed vc4 patches to address, just wanted to clarify this here: The assumption is that all drivers already have a background color of black/0. The background color property would be to set a different background color than black. If the driver has undefined behaviour for instead of an assumed background color of black, then I think that's a driver bug. See https://dri.freedesktop.org/docs/drm/gpu/drm-kms.html#plane-composition-properties "(e.g. for the background color, which currently is not exposed and assumed to be black)" I'm still hoping for some artist to create a nice svg that explains the kms composition model with a nice graphic ... Cheers, Daniel > > drmcrtc.cpp | 11 +++++++++++ > drmcrtc.h | 2 ++ > drmdisplaycompositor.cpp | 15 +++++++++++++++ > 3 files changed, 28 insertions(+) > > diff --git a/drmcrtc.cpp b/drmcrtc.cpp > index 1b354fe..d7bcd7a 100644 > --- a/drmcrtc.cpp > +++ b/drmcrtc.cpp > @@ -52,6 +52,13 @@ int DrmCrtc::Init() { > ALOGE("Failed to get OUT_FENCE_PTR property"); > return ret; > } > + > + ret = drm_->GetCrtcProperty(*this, "background_color", > + &background_color_property_); > + if (ret) { > + ALOGI("Failed to get background_color property"); > + // This is an optional property > + } > return 0; > } > > @@ -86,4 +93,8 @@ const DrmProperty &DrmCrtc::mode_property() const { > const DrmProperty &DrmCrtc::out_fence_ptr_property() const { > return out_fence_ptr_property_; > } > + > +const DrmProperty &DrmCrtc::background_color_property() const { > + return background_color_property_; > +} > } > diff --git a/drmcrtc.h b/drmcrtc.h > index c5a5599..704573a 100644 > --- a/drmcrtc.h > +++ b/drmcrtc.h > @@ -46,6 +46,7 @@ class DrmCrtc { > const DrmProperty &active_property() const; > const DrmProperty &mode_property() const; > const DrmProperty &out_fence_ptr_property() const; > + const DrmProperty &background_color_property() const; > > private: > DrmResources *drm_; > @@ -59,6 +60,7 @@ class DrmCrtc { > DrmProperty active_property_; > DrmProperty mode_property_; > DrmProperty out_fence_ptr_property_; > + DrmProperty background_color_property_; > }; > } > > diff --git a/drmdisplaycompositor.cpp b/drmdisplaycompositor.cpp > index e556e86..69c52dd 100644 > --- a/drmdisplaycompositor.cpp > +++ b/drmdisplaycompositor.cpp > @@ -527,6 +527,21 @@ int DrmDisplayCompositor::CommitFrame(DrmDisplayComposition *display_comp, > return ret; > } > > + if (crtc->background_color_property().id() != 0) { > + // Background color is specified as a 16 bit per channel RGBA value. > + // Set a fully opaque black background as Android HWC expects. > + const uint64_t background_color = 0xFFFF; > + > + ret = drmModeAtomicAddProperty(pset, crtc->id(), > + crtc->background_color_property().id(), > + background_color) < 0; > + if (ret) { > + ALOGE("Failed to add CRTC background_color to pset: %d", ret); > + drmModeAtomicFree(pset); > + return ret; > + } > + } > + > ret = drmModeAtomicAddProperty(pset, crtc->id(), crtc->mode_property().id(), > mode_.blob_id) < 0 || > drmModeAtomicAddProperty(pset, connector->id(), > -- > 2.7.4 > > _______________________________________________ > 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 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
