Bugzilla – Bug 1182349
WARNING: CPU: 7 PID: 90 at ../drivers/gpu/drm/i915/display/intel_dp.c:1895 intel_dp_max_link_rate+0x7e/0xa0
Last modified: 2022-02-18 09:44:34 UTC
Trying to feed an external EDID for i915 to facilitate headless operation on an Intel NUC resulted in repeated warnings
Feb 17 08:47:38 localhost kernel: ------------[ cut here ]------------
Feb 17 08:47:38 localhost kernel: i915 0000:00:02.0: drm_WARN_ON(len <= 0)
Feb 17 08:47:38 localhost kernel: WARNING: CPU: 7 PID: 90 at ../drivers/gpu/drm/i915/display/in>
and a non-working display.
(Arguably the display doesn't work as it's headless, but the vncviewer for Intel AMT stays blank, too. It doesn't when a monitor is connected.)
Created attachment 846192 [details]
Created attachment 846193 [details]
AFAIK, the WARN_ON() has been always present in that function.
Didn't this appear in the earlier kernels?
Anyway, the obvious "fix" should be just to drop WARN_ON(). It makes no sense to trigger a kernel WARNING with stack trace for the data that can be provided externally. It could be at most a debug message.
Has anything happened here? Has it been brought up in upstream?