Re: [PATCH 1/3] drm/i915: don't set modes for 2 connectors on the same encoder

[Damien Lespiau <damien.lespiau@intel.com>]

On Tue, Jan 07, 2014 at 02:55:53PM -0200, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
> 
> In some cases we have more than 1 connector associated to an encoder
> (e.g., SDVO, Haswell DP/HDMI) and we can only set a mode for one of
> these connectors. If we only allowed modesets for connected connectors
> we would never need this patch, but since we do allow modeset for
> disconnected connectors we may see user space trying to set modes on
> the two connectors attached to the same encoder, so we need to forbid
> that.
> 
> This problem can be reproduced by running the following
> intel-gpu-tools test case:
>   ./kms_setmode --run-subtest clone-exclusive-crtc
> 
> Thanks to Daniel Vetter for providing a version of this patch on
> pastebin.
> 
> Credits-to: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>

The comment telling what the block does could use a little update, in
any case:

Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>

I can't review patch 3/3 as I wrote a part of it, we need to find a
victim.

-- 
Damien

> ---
>  drivers/gpu/drm/i915/intel_display.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index a562eef..7cc67b3 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -9922,17 +9922,21 @@ intel_modeset_stage_output_state(struct drm_device *dev,
>  	/* Check for any encoders that needs to be disabled. */
>  	list_for_each_entry(encoder, &dev->mode_config.encoder_list,
>  			    base.head) {
> +		int num_connectors = 0;
>  		list_for_each_entry(connector,
>  				    &dev->mode_config.connector_list,
>  				    base.head) {
>  			if (connector->new_encoder == encoder) {
>  				WARN_ON(!connector->new_encoder->new_crtc);
> -
> -				goto next_encoder;
> +				num_connectors++;
>  			}
>  		}
> -		encoder->new_crtc = NULL;
> -next_encoder:
> +
> +		if (num_connectors == 0)
> +			encoder->new_crtc = NULL;
> +		else if (num_connectors > 1)
> +			return -EINVAL;
> +
>  		/* Only now check for crtc changes so we don't miss encoders
>  		 * that will be disabled. */
>  		if (&encoder->new_crtc->base != encoder->base.crtc) {
> -- 
> 1.8.4.2
> 
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