I have a LG 31MU97-B monitor. My understanding is that EDID does not have a way to report itself as a 4096x2160 monitor, so it reports itself as a 3840x2160 monitor. The mode that it actually supports for it's native resolution that I've been using looks like this:
xrandr --newmode "4096x2160_60" 556.730 4096 4104 4136 4176 2160 2208 2216 2222 +hsync +vsync
I can use this mode with X and it works fine, but I've been unable to get it to work with KMS and Wayland, since it uses the EDID. EDID has CEA extensions that can support some 4096x2160 video modes, but I've tried them, and they don't work since they're not exactly the modeline that it needs.
I've found these DMT modes in drm_edid.c that seems like they would probably work:
/* 0x57 - 4096x2160@60Hz RB */
{ DRM_MODE("4096x2160", DRM_MODE_TYPE_DRIVER, 556744, 4096, 4104,
4136, 4176, 0, 2160, 2208, 2216, 2222, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_NVSYNC) },
/* 0x58 - 4096x2160@59.94Hz RB */
{ DRM_MODE("4096x2160", DRM_MODE_TYPE_DRIVER, 556188, 4096, 4104,
4136, 4176, 0, 2160, 2208, 2216, 2222, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_NVSYNC) },
But... even if I manage to get the code to infer modes on my monitor, it'll reject them since the horizontal resolution is 4096 which is higher than the 3840 that my monitor's EDID reports.
If I wanted to fix this for everyone, what would the proper fix even look like? Should this be added as a quirk for this monitor to force add the modes?
Thanks,
Brian Vincent
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