[Bug 94921] Remove illogical/bogus "Automatic" mode from "Broadcast RGB" property

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=94921

--- Comment #16 from Nicholas Stommel (nicholas.stommel at gmail.com) ---
Tom, I am quite glad you could reopen this. I have tried several monitors that
take DisplayPort inputs and the result is the same: limited RGB. As consumers,
we simply *can't* know whether a certain monitor will automagically be set to
full range RGB until we purchase it, and other times we don't have much choice
(like in an educational or work environment). The fact that a variety of HP,
Dell, Samsung, monitors I've tried default to limited RGB over Displayport
using Intel graphics *only on Linux* makes no sense whatsoever. Even if the
monitors do/don't conform to the Displayport spec, we also cannot expect
manufacturers to include hardware settings for color that very well might get
ignored by software anyway. Personally, I have never seen a single monitor with
limited/full color settings builtin the hardware. 

The hands-down strangest thing I've seen yet regarding this illogical
color-range-by-mode thing Intel is doing occured with a monitor including AMD
Freesync settings that increased the hardware reported refresh rate, somehow
tricking the kernel to send a full RGB signal only when the display was at an
overclocked refresh rate. Monitor modes should simply not be directly connected
to color range output at all. 

The best solution by far would be to implement and allow passing kernel
parameters regarding things like color range for the i915 module as you (and
many others) have suggested. Even with the proptest hack proposed elsewhere for
Wayland, KMS things like Plymouth are still stuck in awful limited RGB.
Ultimately, this demands a kernel-level fix going forward. Why Intel
deliberately chose to regress their Linux drivers by defaulting to limited RGB
makes no sense at all, especially when it's clear what they are currently doing
(basing color range on display mode) is unhelpful and often incorrect by
default for many less well-informed consumers. No monitors I am aware of are
even currently manufactured with only AV limited RGB available. Defaulting to
full RGB over DP regardless of manufacturing idiosyncrasies just makes sense
here, even the Intel patch you referenced from 2013 said as much. 

See, I would love more than anything to have an AMD GPU at my disposal, but as
it stands, I have no choice other than Intel integrated graphics on my
Elitedesk 800 G3 Desktop Mini enterprise machine. Unfortunately, many other
consumers and enterprise users have little choice either. Intel has an
incredibly massive share of the market. Something even more upsetting to me
about Intel's kernel changes is that the LSPCON HDMI connector on my system
board is no longer working properly as of kernels 4.16 and above (there is an
active Redhat Fedora bug report open), so I'm generally stuck with using
Displayport only. 

I'm finding it somewhat difficult to even repatch the 4.17 kernel to default
outputting full RGB, as all sorts of things have radically changed in three
years. Could you perhaps update the patch?

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