drm: understanding the kernel warning during drm_vblank_cleanup()

[Ahsan Hussain]

Hi folks,

I'm new to DRM and trying to understand the warning in 
drivers/gpu/drm/drm_vblank.c during drm_vblank_cleanup().

WARN_ON(READ_ONCE(vblank->enabled) &&
    drm_core_check_feature(dev, DRIVER_MODESET));

Is the drm driver responsible for making sure that !(vblank->enabled) in 
the .unbind operation, or is this something related to userspace? What 
does the warning signify? Git history did not help here at all.


Regards,

Ahsan.