[PATCH v3 1/3] drm/bridge: introduce bridge detaching mechanism

[Daniel Vetter]

On Thu, Aug 25, 2016 at 11:04:32AM +0200, Andrea Merello wrote:
> Up to now, once a bridge has been attached to a DRM device, it cannot
> be undone.
> 
> In particular you couldn't rmmod/insmod a DRM driver that uses a bridge,
> because the bridge would remain bound to the first (dead) driver instance.
> 
> This patch fixes this by introducing drm_encoder_detach() and a ->detach
> callback in drm_bridge_funcs for the bridge to be notified about detaches.
> 
> It's DRM/KMS driver responsibility to call drm_encoder_detach().
> 
> While adding the bridge detach callback, with its kerneldoc, I also added
> kerneldoc for attach callback.
> 
> Few other kerneldocs fixes around there are included.
> 
> Suggested-by: Daniel Vetter <daniel at ffwll.ch>
> Suggested-by: Lucas Stach <l.stach at pengutronix.de>
> Signed-off-by: Andrea Merello <andrea.merello at gmail.com>
> Cc: Archit Taneja <architt at codeaurora.org>
> Cc: David Airlie <airlied at linux.ie>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Lucas Stach <l.stach at pengutronix.de>

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

As discussed on the last round, I'll let Archit apply all 3 to drm-misc,
so he can check them out too.
-Daniel
> ---
>  drivers/gpu/drm/drm_bridge.c | 29 +++++++++++++++++++++++++++--
>  include/drm/drm_crtc.h       | 26 +++++++++++++++++++++++++-
>  2 files changed, 52 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 2555430..4840466 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -98,11 +98,11 @@ EXPORT_SYMBOL(drm_bridge_remove);
>   * @dev: DRM device
>   * @bridge: bridge control structure
>   *
> - * called by a kms driver to link one of our encoder/bridge to the given
> + * Called by a kms driver to link one of our encoder/bridge to the given
>   * bridge.
>   *
>   * Note that setting up links between the bridge and our encoder/bridge
> - * objects needs to be handled by the kms driver itself
> + * objects needs to be handled by the kms driver itself.
>   *
>   * RETURNS:
>   * Zero on success, error code on failure
> @@ -125,6 +125,31 @@ int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge)
>  EXPORT_SYMBOL(drm_bridge_attach);
>  
>  /**
> + * drm_bridge_detach - deassociate given bridge from its DRM device
> + *
> + * @bridge: bridge control structure
> + *
> + * Called by a kms driver to unlink the given bridge from its DRM device.
> + *
> + * Note that tearing down links between the bridge and our encoder/bridge
> + * objects needs to be handled by the kms driver itself.
> + */
> +void drm_bridge_detach(struct drm_bridge *bridge)
> +{
> +	if (WARN_ON(!bridge))
> +		return;
> +
> +	if (WARN_ON(!bridge->dev))
> +		return;
> +
> +	if (bridge->funcs->detach)
> +		bridge->funcs->detach(bridge);
> +
> +	bridge->dev = NULL;
> +}
> +EXPORT_SYMBOL(drm_bridge_detach);
> +
> +/**
>   * DOC: bridge callbacks
>   *
>   * The &drm_bridge_funcs ops are populated by the bridge driver. The DRM
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 3fa0275..bb214a1 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1118,12 +1118,33 @@ struct drm_plane {
>  
>  /**
>   * struct drm_bridge_funcs - drm_bridge control functions
> - * @attach: Called during drm_bridge_attach
>   */
>  struct drm_bridge_funcs {
> +	/**
> +	 * @attach:
> +	 *
> +	 * This callback is invoked whenever our bridge is being attached to a
> +	 * &drm_encoder.
> +	 *
> +	 * The attach callback is optional.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * Zero on success, error code on failure.
> +	 */
>  	int (*attach)(struct drm_bridge *bridge);
>  
>  	/**
> +	 * @detach:
> +	 *
> +	 * This callback is invoked whenever our bridge is being detached from a
> +	 * &drm_encoder.
> +	 *
> +	 * The detach callback is optional.
> +	 */
> +	void (*detach)(struct drm_bridge *bridge);
> +
> +	/**
>  	 * @mode_fixup:
>  	 *
>  	 * This callback is used to validate and adjust a mode. The paramater
> @@ -1137,6 +1158,8 @@ struct drm_bridge_funcs {
>  	 * this function passes all other callbacks must succeed for this
>  	 * configuration.
>  	 *
> +	 * The mode_fixup callback is optional.
> +	 *
>  	 * NOTE:
>  	 *
>  	 * This function is called in the check phase of atomic modesets, which
> @@ -2426,6 +2449,7 @@ extern int drm_bridge_add(struct drm_bridge *bridge);
>  extern void drm_bridge_remove(struct drm_bridge *bridge);
>  extern struct drm_bridge *of_drm_find_bridge(struct device_node *np);
>  extern int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge);
> +extern void drm_bridge_detach(struct drm_bridge *bridge);
>  
>  bool drm_bridge_mode_fixup(struct drm_bridge *bridge,
>  			const struct drm_display_mode *mode,
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch