Hi, On Tue, Feb 20, 2018 at 04:10:28PM +0100, Stefan Schake wrote: > On Fri, Feb 16, 2018 at 7:20 PM, Ville Syrjälä > <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > On Fri, Feb 16, 2018 at 06:39:29PM +0100, Maxime Ripard wrote: > >> Some drivers duplicate the logic to create a property to store a per-plane > >> alpha. > >> > >> This is especially useful if we ever want to support extra protocols for > >> Wayland like: > >> https://lists.freedesktop.org/archives/wayland-devel/2017-August/034741.html > >> > >> Let's create a helper in order to move that to the core. > >> > >> Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > >> Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx> > >> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxx> > >> --- > >> Documentation/gpu/kms-properties.csv | 2 +- > >> drivers/gpu/drm/drm_atomic.c | 4 ++++- > >> drivers/gpu/drm/drm_atomic_helper.c | 4 ++++- > >> drivers/gpu/drm/drm_blend.c | 32 +++++++++++++++++++++++++++++- > >> include/drm/drm_blend.h | 1 +- > >> include/drm/drm_plane.h | 6 +++++- > >> 6 files changed, 48 insertions(+), 1 deletion(-) > >> > >> diff --git a/Documentation/gpu/kms-properties.csv b/Documentation/gpu/kms-properties.csv > >> index 927b65e14219..25ad3503d663 100644 > >> --- a/Documentation/gpu/kms-properties.csv > >> +++ b/Documentation/gpu/kms-properties.csv > >> @@ -99,5 +99,5 @@ radeon,DVI-I,“coherent”,RANGE,"Min=0, Max=1",Connector,TBD > >> ,,"""underscan vborder""",RANGE,"Min=0, Max=128",Connector,TBD > >> ,Audio,“audio”,ENUM,"{ ""off"", ""on"", ""auto"" }",Connector,TBD > >> ,FMT Dithering,“dither”,ENUM,"{ ""off"", ""on"" }",Connector,TBD > >> -rcar-du,Generic,"""alpha""",RANGE,"Min=0, Max=255",Plane,TBD > >> +,,"""alpha""",RANGE,"Min=0, Max=Driver dependant",Plane,Opacity of the plane from transparent (0) to fully opaque (MAX). If this property is set to a value different than max, and that the pixel will define an alpha component, the property will have precendance and the pixel value will be ignored. > > > > Those semantics don't seem particularly good to me. I think we would want the > > per-pixel alpha and global alpha both to be effecive at the same time. You can > > always decide to ignore the per-pixel alpha by using a pixel format without > > alpha. > > > > Also, where's the userspace that wants this feature? > > drm_hwcomposer uses an 8-bit per-plane alpha property, and from what I > can tell the semantics are that both pixel and plane alpha apply > simultaneously if present. > Here is what I think was the kernel-side for this: > > https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/306122 > > I've added Sean Paul, he might be able to give a more definitive answer. What is the behaviour of the tegra engine when it has both a pixel-alpha and a plane-alpha? Atmel at least will drop one (but I'm not sure which one anymore). Thanks! Maxime -- Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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