HDMI Aspect Ratio

[Lloyd Atkinson]

Hi folks,

We're looking at 4K HDMI mode support, and noticed aspect ratio support
is in flux.

Aspect ratio parsing was added to the mode:
https://patchwork.kernel.org/patch/9271401/

But later reverted:
https://patchwork.kernel.org/patch/9410765/

We're finding that since aspect ratio information isn't supported, modes
conflict, and the userspace isn't able to see the full list of modes.

Similarly, there's a case where two modes differ only by aspect_ratio
and vrefresh. In drm_edid.c, within drm_display_mode_from_vic_index,
newmode->vrefresh is forcibly being cleared to 0. Since refresh rate is
forced to 0, and aspect ratio isn’t considered in general, the modes
collide and we can’t advertise one of the modes.

https://github.com/torvalds/linux/blob/v4.14-rc4/drivers/gpu/drm/drm_edid.c#L3153

Have there been any follow-up discussions on this topic?

What is the reason to clear the vrefresh within
drm_display_mode_from_vic_index?

Thanks,
Lloyd Atkinson

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