[PATCH (repost) 1/5] drm_dp_cec: check that aux has a transfer function

[Lyude Paul]

On Fri, 2018-08-17 at 16:11 +0200, Hans Verkuil wrote:
> From: Hans Verkuil <hans.verkuil at cisco.com>
> 
> If aux->transfer == NULL, then just return without doing
> anything. In that case the function is likely called for
> a non-(e)DP connector.
> 
> This never happened for the i915 driver, but the nouveau and amdgpu
> drivers need this check.
Could you give a backtrace from where you're hitting this issue with nouveau and
amdgpu? It doesn't make a whole ton of sense to have connectors registering DP
aux busses if they aren't actually DP, that should probably just be fixed...

> 
> The alternative would be to add this check in those drivers before
> every drm_dp_cec call, but it makes sense to check it in the
> drm_dp_cec functions to prevent a kernel oops.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
> ---
>  drivers/gpu/drm/drm_dp_cec.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
> index 988513346e9c..1407b13a8d5d 100644
> --- a/drivers/gpu/drm/drm_dp_cec.c
> +++ b/drivers/gpu/drm/drm_dp_cec.c
> @@ -238,6 +238,10 @@ void drm_dp_cec_irq(struct drm_dp_aux *aux)
>  	u8 cec_irq;
>  	int ret;
>  
> +	/* No transfer function was set, so not a DP connector */
> +	if (!aux->transfer)
> +		return;
> +
>  	mutex_lock(&aux->cec.lock);
>  	if (!aux->cec.adap)
>  		goto unlock;
> @@ -293,6 +297,10 @@ void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const
> struct edid *edid)
>  	unsigned int num_las = 1;
>  	u8 cap;
>  
> +	/* No transfer function was set, so not a DP connector */
> +	if (!aux->transfer)
> +		return;
> +
>  #ifndef CONFIG_MEDIA_CEC_RC
>  	/*
>  	 * CEC_CAP_RC is part of CEC_CAP_DEFAULTS, but it is stripped by
> @@ -361,6 +369,10 @@ EXPORT_SYMBOL(drm_dp_cec_set_edid);
>   */
>  void drm_dp_cec_unset_edid(struct drm_dp_aux *aux)
>  {
> +	/* No transfer function was set, so not a DP connector */
> +	if (!aux->transfer)
> +		return;
> +
>  	cancel_delayed_work_sync(&aux->cec.unregister_work);
>  
>  	mutex_lock(&aux->cec.lock);
> @@ -404,6 +416,8 @@ void drm_dp_cec_register_connector(struct drm_dp_aux *aux,
> const char *name,
>  				   struct device *parent)
>  {
>  	WARN_ON(aux->cec.adap);
> +	if (WARN_ON(!aux->transfer))
> +		return;
>  	aux->cec.name = name;
>  	aux->cec.parent = parent;
>  	INIT_DELAYED_WORK(&aux->cec.unregister_work,