[S] Change in coreboot[main]: soc/intel/cmn/gfx: Add API to report presence of external display

[Subrata Banik (Code Review)]

Attention is currently required from: Arthur Heymans, Julius Werner, Kapil Porwal, Lean Sheng Tan, Nick Vaccaro, Werner Zeh.

Subrata Banik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78080?usp=email )

Change subject: soc/intel/cmn/gfx: Add API to report presence of external display
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Patch Set 1:

(1 comment)

File src/soc/intel/common/block/graphics/graphics.c:

https://review.coreboot.org/c/coreboot/+/78080/comment/77bba6be_48376b40 :
PS1, Line 59: #if CONFIG(REPORT_EXTERNAL_DISPLAY_AT_PREBOOT)
> So you're saying that those other platforms would return 0 from report_external_display() (because they would always initialize the eDP display), which is the same as the stub function you implemented for when the Kconfig is disabled? Sounds like that would work fine to me.

yes, your understanding is correct
> The point is to just reduce the number of Kconfig options and special cases to keep track of, to make the code easier to follow. Especially if this only affects older boards and we're planning to have the external display initialization in that case for all future devices, I don't think there's a problem with making some older platforms read a few pointless (but harmless) registers, if it helps simplify things a bit.

I'm not sure if it's harmless bt I can seek some help from community to test this code on SKL and other generations like JSL etc.