On Mon, Mar 26, 2018 at 11:01:53PM +0800, Chen-Yu Tsai wrote: > On Mon, Mar 26, 2018 at 10:45 PM, Maxime Ripard > <maxime.ripard@xxxxxxxxxxx> wrote: > > 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. > > Looks like it's 32x32 pixels with an 8-bit (max) palette, with full RGBA > for the colors in the palette. I don't see the 1 bit alpha you mentioned. > Looks like this needs some extra work for building the palette and copying > the cursor image. Indeed, you're right. I'm still not sure how it could be turned into something useful though. Maxime -- Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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