[Intel-gfx] [PATCH] drm/atomic: Fix the early return in drm_atomic_set_mode_for_crtc()

[Daniel Vetter]

On Tue, Nov 20, 2018 at 07:55:42PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The early return in drm_atomic_set_mode_for_crtc() isn't quite
> right. It would mistakenly return and fail to update
> crtc_state->enable if someone actually tried to set a zeroed
> mode on a currently disabled crtc. I suppose that should never
> happen but better safe than sorry.
> 
> Additionally the early return will not be taken if we're trying to
> disable an already disable crtc. While that is not actually harmful
> it is inconsistent, so let's handle that case as well.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Do we have an igt for this? I.e. trying to set a all-0 mode for a disabled
CRTC and seeing what happens ...

Patch itself looks fine, has my r-b if the igt materializes.
-Daniel

> ---
>  drivers/gpu/drm/drm_atomic_uapi.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index 86ac33922b09..ed0ea82e8a1d 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -68,8 +68,13 @@ int drm_atomic_set_mode_for_crtc(struct drm_crtc_state *state,
>  	struct drm_mode_modeinfo umode;
>  
>  	/* Early return for no change. */
> -	if (mode && memcmp(&state->mode, mode, sizeof(*mode)) == 0)
> -		return 0;
> +	if (state->enable) {
> +		if (mode && memcmp(&state->mode, mode, sizeof(*mode)) == 0)
> +			return 0;
> +	} else {
> +		if (!mode)
> +			return 0;
> +	}
>  
>  	drm_property_blob_put(state->mode_blob);
>  	state->mode_blob = NULL;
> -- 
> 2.18.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch