linux-kernel - Re: [PATCH v5 2/6] drm/bridge: Add a devm

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Message-ID: <2023170.2CE3xBA9bq@avalon>
Date:   Fri, 04 Aug 2017 16:46:24 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Eric Anholt <eric@...olt.net>
Cc:     dri-devel@...ts.freedesktop.org,
        Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-kernel@...r.kernel.org, Daniel Vetter <daniel.vetter@...l.ch>
Subject: Re: [PATCH v5 2/6] drm/bridge: Add a devm_ allocator for panel bridge.

Hi Eric,

(CC'ing Daniel)

Thank you for the patch.

On Tuesday 18 Jul 2017 14:05:06 Eric Anholt wrote:
> This will let drivers reduce the error cleanup they need, in
> particular the "is_panel_bridge" flag.
> 
> v2: Slight cleanup of remove function by Andrzej

I just want to point out that, in the context of Daniel's work on hot-unplug, 
90% of the devm_* allocations are wrong and will get in the way. All DRM core 
objects that are accessible one way or another from userspace will need to be 
properly reference-counted and freed only when the last reference disappears, 
which could be well after the corresponding device is removed. I believe this 
could be one such objects :-/

> Signed-off-by: Eric Anholt <eric@...olt.net>
> Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> ---
>  drivers/gpu/drm/bridge/panel.c | 30 ++++++++++++++++++++++++++++++
>  include/drm/drm_bridge.h       |  3 +++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
> index 685c1a480201..292ee92a9c97 100644
> --- a/drivers/gpu/drm/bridge/panel.c
> +++ b/drivers/gpu/drm/bridge/panel.c
> @@ -195,3 +195,33 @@ void drm_panel_bridge_remove(struct drm_bridge *bridge)
> devm_kfree(panel_bridge->panel->dev, bridge);
>  }
>  EXPORT_SYMBOL(drm_panel_bridge_remove);
> +
> +static void devm_drm_panel_bridge_release(struct device *dev, void *res)
> +{
> +	struct drm_bridge **bridge = res;
> +
> +	drm_panel_bridge_remove(*bridge);
> +}
> +
> +struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
> +					     struct drm_panel *panel,
> +					     u32 connector_type)
> +{
> +	struct drm_bridge **ptr, *bridge;
> +
> +	ptr = devres_alloc(devm_drm_panel_bridge_release, sizeof(*ptr),
> +			   GFP_KERNEL);
> +	if (!ptr)
> +		return ERR_PTR(-ENOMEM);
> +
> +	bridge = drm_panel_bridge_add(panel, connector_type);
> +	if (!IS_ERR(bridge)) {
> +		*ptr = bridge;
> +		devres_add(dev, ptr);
> +	} else {
> +		devres_free(ptr);
> +	}
> +
> +	return bridge;
> +}
> +EXPORT_SYMBOL(devm_drm_panel_bridge_add);
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 1dc94d5392e2..6522d4cbc9d9 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -268,6 +268,9 @@ void drm_bridge_enable(struct drm_bridge *bridge);
>  struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel,
>  					u32 connector_type);
>  void drm_panel_bridge_remove(struct drm_bridge *bridge);
> +struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
> +					     struct drm_panel *panel,
> +					     u32 connector_type);
>  #endif
> 
>  #endif

-- 
Regards,

Laurent Pinchart