On Fri, 9 Oct 2020 16:10:25 +0300 Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > On Fri, Oct 09, 2020 at 01:07:20PM +0100, Daniel Stone wrote: > > Hi, > > > > On Fri, 9 Oct 2020 at 10:24, Simon Ser <contact@xxxxxxxxxxx> wrote: > > > User-space should avoid parsing EDIDs for metadata already exposed via > > > other KMS interfaces and properties. For instance, user-space should not > > > try to extract a list of modes from the EDID: the kernel might mutate > > > the mode list (because of link capabilities or quirks for instance). > > > > > > Other metadata not exposed by KMS can be parsed by user-space. This > > > includes for instance monitor identification (make/model/serial) and > > > supported color-spaces. > > > > So I take it the only way to get modes is through the connector's list > > of modes. That sounds reasonable enough to me, but I think to properly > > handle colour (e.g. CEA modes have different behaviour for > > limited/full range depending on which VIC they correspond to IIRC) > > If the mode has a VIC and that VIC is not 1, then it's limited range, > otherwise full range. There are fortunately no cases where you would > have the same exact timings corresponding to different quantization > range depending on the VIC. > > And the only reason the same timings could correspond to multiple VICs > is aspect ratio. Which is already exposed via the mode flags, assuming > the appropriate client cap is enabled. > > So I think the only reason to expose the VIC would be if userspace is > non-lazy and wants to manage its colors presicely, but is otherwise lazy > and doesn't want to figure out what the VIC of the mode is on its own. What would "figure out what the VIC of the mode is" require in userspace? A database of all VIC modes and then compare if the detailed timings match? Is that also how the kernel recognises that userspace wants to set a certain VIC mode instead of some arbitrary mode? Can CVT or GVT produce those exact timings? Can that accidentally result in limited range? Sounds like the hypothetical libedid needs a libvic as a friend... and libpixel-format while at it. :-) Thanks, pq
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