linux-kernel - Re: [PATCH 1/2] drm/connector: allow a .destroy callback for drmm-allocated connectors

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Message-ID: <ycbx4fxqppxuopcd64i6lt7qlcsa75iv4z6q4aka7igt7pntc7@bf3toot46wxo>
Date: Fri, 26 Sep 2025 01:07:26 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Hui Pu <Hui.Pu@...ealthcare.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] drm/connector: allow a .destroy callback for
 drmm-allocated connectors

On Thu, Sep 25, 2025 at 07:19:49PM +0200, Luca Ceresoli wrote:
> Some code is going to need connector-specific cleanup actions (namely
> drm_bridge_connector will need to put refcounted bridges).
> 
> The .destroy callback is appropriate for this task but it is currently
> forbidden by drmm_connector_init(). Relax this limitation and document it.
> 
> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
> 
> ---
> 
> The other obvious approach would be adding a separate .cleanup callback for
> the cleanup-only actions. I tried both, they both apparently work, so any
> arguments and opinions on which approach is best within the overall DRM
> design would be very useful here.

Would it be better to use drmm-reset actions. I think the check here
makes much more help overall than harm in your case, so I'd suggest
leaving it in place.

> ---
>  drivers/gpu/drm/drm_connector.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 272d6254ea4784e97ca894ec4d463beebf9fdbf0..bd0220513a23afcb096b0c4c4d2b957b81f21ee1 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -513,7 +513,8 @@ static void drm_connector_cleanup_action(struct drm_device *dev,
>   *
>   * The connector structure should be allocated with drmm_kzalloc().
>   *
> - * The @drm_connector_funcs.destroy hook must be NULL.
> + * The @drm_connector_funcs.destroy hook must only do connector-specific
> + * cleanups if any is needed, not dealloacte the connector.
>   *
>   * Returns:
>   * Zero on success, error code on failure.
> @@ -526,9 +527,6 @@ int drmm_connector_init(struct drm_device *dev,
>  {
>  	int ret;
>  
> -	if (drm_WARN_ON(dev, funcs && funcs->destroy))
> -		return -EINVAL;
> -
>  	ret = drm_connector_init_and_add(dev, connector, funcs, connector_type, ddc);
>  	if (ret)
>  		return ret;
> 
> -- 
> 2.51.0
> 

-- 
With best wishes
Dmitry