Re: [PATCH v2] drm/display: use ERR_PTR on DP tunnel manager creation fail

[Andi Shyti <andi.shyti@linux.intel.com>]

Hi Krzysztof,

On Wed, Dec 11, 2024 at 02:52:20PM +0000, Krzysztof Karas wrote:
> Instead of returning a generic NULL on error from drm_dp_tunnel_mgr_create(),
> use error pointers with informative codes. This will also trigger IS_ERR() in
> current caller (intel_dp_tunnerl_mgr_init()) instead of bypassing it via NULL
> pointer.

I was about to suggest fixing either this or his counterpart in
the header file.

Please send this in a series along with the previous patch in
order to let people understand why you are sending this.

Besides, I think you can improve the explanation here, which is
the different behaviour of drm_dp_tunnel_mgr_create() depending
on the CONFIG_DRM_DISPLAY_DP_TUNNEL config flag.

You can add to both of them my r-b.

Did you check who is maintaining this file?

Andi

> v2: use error codes inside drm_dp_tunnel_mgr_create() instead of handling
>  on caller's side (Michal, Imre)
> 
> Signed-off-by: Krzysztof Karas <krzysztof.karas@intel.com>
> ---
>  drivers/gpu/drm/display/drm_dp_tunnel.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_tunnel.c b/drivers/gpu/drm/display/drm_dp_tunnel.c
> index 48b2df120086..90fe07a89260 100644
> --- a/drivers/gpu/drm/display/drm_dp_tunnel.c
> +++ b/drivers/gpu/drm/display/drm_dp_tunnel.c
> @@ -1896,8 +1896,8 @@ static void destroy_mgr(struct drm_dp_tunnel_mgr *mgr)
>   *
>   * Creates a DP tunnel manager for @dev.
>   *
> - * Returns a pointer to the tunnel manager if created successfully or NULL in
> - * case of an error.
> + * Returns a pointer to the tunnel manager if created successfully or error
> + * pointer in case of failure.
>   */
>  struct drm_dp_tunnel_mgr *
>  drm_dp_tunnel_mgr_create(struct drm_device *dev, int max_group_count)
> @@ -1907,7 +1907,7 @@ drm_dp_tunnel_mgr_create(struct drm_device *dev, int max_group_count)
>  
>  	mgr = kzalloc(sizeof(*mgr), GFP_KERNEL);
>  	if (!mgr)
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>  
>  	mgr->dev = dev;
>  	init_waitqueue_head(&mgr->bw_req_queue);
> @@ -1916,7 +1916,7 @@ drm_dp_tunnel_mgr_create(struct drm_device *dev, int max_group_count)
>  	if (!mgr->groups) {
>  		kfree(mgr);
>  
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>  	}
>  
>  #ifdef CONFIG_DRM_DISPLAY_DP_TUNNEL_STATE_DEBUG
> @@ -1927,7 +1927,7 @@ drm_dp_tunnel_mgr_create(struct drm_device *dev, int max_group_count)
>  		if (!init_group(mgr, &mgr->groups[i])) {
>  			destroy_mgr(mgr);
>  
> -			return NULL;
> +			return ERR_PTR(-ENOMEM);
>  		}
>  
>  		mgr->group_count++;
> -- 
> 2.34.1