[PATCH] drm: add debug logs for drm_mode_atomic_ioctl errors

[Ville Syrjälä]

On Tue, Nov 10, 2020 at 03:58:01PM +0000, Simon Ser wrote:
> Be nice to user-space and log what happened when returning EINVAL in
> drm_mode_atomic_ioctl.
> 
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <mripard at kernel.org>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> ---
>  drivers/gpu/drm/drm_atomic_uapi.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index 25c269bc4681..68d767420082 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -1303,22 +1303,30 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  	 * though this may be a bit overkill, since legacy userspace
>  	 * wouldn't know how to call this ioctl)
>  	 */
> -	if (!file_priv->atomic)
> +	if (!file_priv->atomic) {
> +		DRM_DEBUG_ATOMIC("atomic commit failed: atomic cap not enabled\n");

The "atomic commit failed:" bit seems a bit redundant.

>  		return -EINVAL;
> +	}
>  
> -	if (arg->flags & ~DRM_MODE_ATOMIC_FLAGS)
> +	if (arg->flags & ~DRM_MODE_ATOMIC_FLAGS) {
> +		DRM_DEBUG_ATOMIC("atomic commit failed: invalid flag\n");
>  		return -EINVAL;
> +	}
>  
>  	if (arg->reserved)
>  		return -EINVAL;

You don't want one for this? I wonder why this "reserved" field
even exists...

>  
> -	if (arg->flags & DRM_MODE_PAGE_FLIP_ASYNC)
> +	if (arg->flags & DRM_MODE_PAGE_FLIP_ASYNC) {
> +		DRM_DEBUG_ATOMIC("atomic commit failed: invalid flag DRM_MODE_PAGE_FLIP_ASYNC\n");
>  		return -EINVAL;
> +	}
>  
>  	/* can't test and expect an event at the same time. */
>  	if ((arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) &&
> -			(arg->flags & DRM_MODE_PAGE_FLIP_EVENT))
> +			(arg->flags & DRM_MODE_PAGE_FLIP_EVENT)) {
> +		DRM_DEBUG_ATOMIC("atomic commit failed: page-flip event requested with test-only commit\n");
>  		return -EINVAL;
> +	}
>  
>  	state = drm_atomic_state_alloc(dev);
>  	if (!state)
> -- 
> 2.29.2
> 
> 
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-- 
Ville Syrjälä
Intel