[PATCH] drm/exynos: fix vblank handling during dpms off

[Russell King - ARM Linux]

On Thu, Oct 09, 2014 at 02:43:02PM +0900, Alexandre Courbot wrote:
> But there might be another issue, which is that calls to  
> drm_vblank_get() will return -EINVAL if invoked between drm_blank_off  
> and drm_blank_on. Is this really the desired behavior? Can it at least  
> happen? If so, how are drivers supposed to react to this situation?

I've not yet seen the commit which causes this problem, but I hope
that drm_wait_vblank() isn't affected by this.  In current mainline,
drm_vblank_get() is used inside drm_wait_vblank(), which is called as
a result of userspace calling DRM_IOCTL_WAIT_VBLANK.

So, what is the effect of this change on user applications making use
of the vblank wait ioctl - and is that change intended?

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