On Mon, Mar 26, 2018 at 10:22:45PM +0800, Chen-Yu Tsai wrote: > On Mon, Mar 26, 2018 at 10:14 PM, Joonas Kylmälä <joonas.kylmala@xxxxxx> wrote: > > Hi DRM subsystem developers, > > > > I ran into this patch where overlay plane was switched to cursor plane > > because there was no proper cursor plane available on the display > > hardware: <https://lkml.org/lkml/2018/3/17/120>. Can we discuss whether > > to have a policy of using a normal plane for cursor plane in case a > > dedicated HW cursor plane is missing? > > > > Daniel Vetter suggests that it might be fine to use normal plane for > > cursor plane because how to use the plane would be only "a hint to > > userspace" (see the email linked). > > > > My motivation for having this discussion is that the newer Allwinner > > SoCs don't have dedicated HW cursor plane and the sun4i DRM driver > > currently uses the extra planes as overlay planes which makes moving the > > cursor on Xfce4 DE a terrible experience. To have better cursor moving > > experience one overlay plane would need to be sacrificed. > > If you look at the development history, we've never supported cursor planes. X can use an overlay to put the cursor though. > At the beginning we supported one main plane and one overlay plane. That was > it. The Display Engine 1.0 does have support for an extra hardware cursor, > but we haven't done the work to support it yet. I don't know about the > Display Engine 2.0 though. An issue with supporting the hardware cursor we have is that as far as I understood, the cursor plane in DRM has the assumption that it would be an ARGB format. In the first display engine, the format is actually an 8-bit palette with 1 bit of alpha iirc. Maxime -- Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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