Op 29-06-18 om 12:27 schreef Stefan Schake: > Hey Maarten, > > On Fri, Jun 29, 2018 at 12:05 PM, Maarten Lankhorst > <maarten.lankhorst@xxxxxxxxxxxxxxx> wrote: >> Op 22-02-18 om 04:54 schreef Stefan Schake: >>> 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). >> Ping? Would be nice if we were moving forward. :) > I was unclear if DRM specified a black background when writing this. > Someone pointed me towards the excerpt in the docs that explicitly > mandates black background fill and so I ended up writing a VC4 patch > that automatically sets it when required instead of the optional property > used here. > > Adding a background_color property would still be desirable, but I'm > unclear on what the userspace would be at the moment. drm_hwc doesn't > need any background color other than black and since that is the DRM > default, it wouldn't need to use a property. > > Thanks, > Stefan It would still be useful for e-paper displays where the background color would be better suited as white, or when we want to blend a different color than black. But I fear for now there's no real userspace. :( Which is unfortunate, because the series are easy to implement, but it's just a case where there's no need from userspace yet for the hw capability. ~Maarten _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
