On Mon, 22 Nov 2021 19:05:16 +0900 Hector Martin <marcan@xxxxxxxxx> wrote: > On 22/11/2021 18.52, Pekka Paalanen wrote: > > On Wed, 17 Nov 2021 23:58:28 +0900 > > Hector Martin <marcan@xxxxxxxxx> wrote: > > > >> Add XRGB8888 emulation support for devices that can only do XRGB2101010. > >> > >> This is chiefly useful for simpledrm on Apple devices where the > >> bootloader-provided framebuffer is 10-bit, which already works fine with > >> simplefb. This is required to make simpledrm support this too. > >> > >> Signed-off-by: Hector Martin <marcan@xxxxxxxxx> > >> --- > >> drivers/gpu/drm/drm_format_helper.c | 64 +++++++++++++++++++++++++++++ > >> include/drm/drm_format_helper.h | 4 ++ > >> 2 files changed, 68 insertions(+) > > > > Hi Hector, > > > > I'm curious, since the bootloader seems to always set up a 10-bit mode, > > is there a reason for it that you can guess? Is the monitor in WCG or > > even HDR mode? > > My guess is that Apple prefer to use 10-bit framebuffers for seamless > handover with their graphics stack, which presumably uses 10-bit > framebuffers these days. It seems to be unconditional; I've never seen > anything but 10 bits across all Apple devices, both with the internal > panels on laptops and with bog standard external displays on the Mac > Mini via HDMI. HDR is not necessary, even very dumb capture cards and > old screens get a 10-bit framebufer in memory. That makes perfect sense, thanks! Switching between sRGB and WCG or HDR mode is not a modeset, it's just HDMI/DP/whatever metadata/infoframe. > The only time I see an 8-bit framebuffer is with *no* monitor connected > on the Mini, in which case you get an 8-bit 640x1136 dummy framebuffer > (that's the iPhone 5 screen resolution... :-) ) > Thanks, pq
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