Re: [PATCH v2 04/50] drm/bridge: Add connector-related bridge operations and data

[Boris Brezillon <boris.brezillon@collabora.com>]

On Tue, 20 Aug 2019 04:16:35 +0300
Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote:

> To support implementation of DRM connectors on top of DRM bridges
> instead of by bridges, the drm_bridge needs to expose new operations and
> data:
> 
> - Output detection, hot-plug notification, mode retrieval and EDID
>   retrieval operations
> - Bitmask of supported operations
> - Bridge output type
> - I2C adapter for DDC access
> 
> Add and document these.
> 
> Three new bridge helper functions are also added to handle hot plug
> notification in a way that is as transparent as possible for the
> bridges.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
> Changes since v1:
> 
> - Make .hpd_enable() and .hpd_disable() optional
> - Rename .lost_hotplug() to .hpd_notify()
> - Add ddc field to drm_bridge
> ---
>  drivers/gpu/drm/drm_bridge.c |  94 +++++++++++++++++++
>  include/drm/drm_bridge.h     | 177 ++++++++++++++++++++++++++++++++++-
>  2 files changed, 270 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index cba537c99e43..cf1fbed88410 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -70,6 +70,8 @@ static LIST_HEAD(bridge_list);
>   */
>  void drm_bridge_add(struct drm_bridge *bridge)
>  {
> +	mutex_init(&bridge->hpd_mutex);
> +
>  	mutex_lock(&bridge_lock);
>  	list_add_tail(&bridge->list, &bridge_list);
>  	mutex_unlock(&bridge_lock);
> @@ -86,6 +88,8 @@ void drm_bridge_remove(struct drm_bridge *bridge)
>  	mutex_lock(&bridge_lock);
>  	list_del_init(&bridge->list);
>  	mutex_unlock(&bridge_lock);
> +
> +	mutex_destroy(&bridge->hpd_mutex);
>  }
>  EXPORT_SYMBOL(drm_bridge_remove);
>  
> @@ -462,6 +466,96 @@ void drm_atomic_bridge_enable(struct drm_bridge *bridge,
>  }
>  EXPORT_SYMBOL(drm_atomic_bridge_enable);
>  
> +/**
> + * drm_bridge_hpd_enable - enable hot plug detection for the bridge
> + * @bridge: bridge control structure
> + * @cb: hot-plug detection callback
> + * @data: data to be passed to the hot-plug detection callback
> + *
> + * Call &drm_bridge_funcs.hpd_enable if implemented and register the given @cb
> + * and @data as hot plug notification callback. From now on the @cb will be
> + * called with @data when an output status change is detected by the bridge,
> + * until hot plug notification gets disabled with drm_bridge_hpd_disable().
> + *
> + * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
> + * bridge->ops. This function shall not be called when the flag is not set.
> + *
> + * Only one hot plug detection callback can be registered at a time, it is an
> + * error to call this function when hot plug detection is already enabled for
> + * the bridge.
> + */
> +void drm_bridge_hpd_enable(struct drm_bridge *bridge,
> +			   void (*cb)(void *data,
> +				      enum drm_connector_status status),
> +			   void *data)
> +{
> +	if (!bridge || !(bridge->ops & DRM_BRIDGE_OP_HPD))
> +		return;
> +
> +	mutex_lock(&bridge->hpd_mutex);
> +
> +	if (WARN(bridge->hpd_cb, "Hot plug detection already enabled\n"))
> +		goto unlock;
> +
> +	bridge->hpd_cb = cb;
> +	bridge->hpd_data = data;
> +
> +	if (bridge->funcs->hpd_enable)
> +		bridge->funcs->hpd_enable(bridge);
> +
> +unlock:
> +	mutex_unlock(&bridge->hpd_mutex);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_enable);
> +
> +/**
> + * drm_bridge_hpd_disable - disable hot plug detection for the bridge
> + * @bridge: bridge control structure
> + *
> + * Call &drm_bridge_funcs.hpd_disable if implemented and unregister the hot
> + * plug detection callback previously registered with drm_bridge_hpd_enable().
> + * Once this function returns the callback will not be called by the bridge
> + * when an output status change occurs.
> + *
> + * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
> + * bridge->ops. This function shall not be called when the flag is not set.
> + */
> +void drm_bridge_hpd_disable(struct drm_bridge *bridge)
> +{
> +	if (!bridge || !(bridge->ops & DRM_BRIDGE_OP_HPD))
> +		return;
> +
> +	mutex_lock(&bridge->hpd_mutex);
> +	if (bridge->funcs->hpd_disable)
> +		bridge->funcs->hpd_disable(bridge);
> +
> +	bridge->hpd_cb = NULL;
> +	bridge->hpd_data = NULL;
> +	mutex_unlock(&bridge->hpd_mutex);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_disable);
> +
> +/**
> + * drm_bridge_hpd_notify - notify hot plug detection events
> + * @bridge: bridge control structure
> + * @status: output connection status
> + *
> + * Bridge drivers shall call this function to report hot plug events when they
> + * detect a change in the output status, when hot plug detection has been
> + * enabled by drm_bridge_hpd_enable().
> + *
> + * This function shall be called in a context that can sleep.
> + */
> +void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> +			   enum drm_connector_status status)
> +{
> +	mutex_lock(&bridge->hpd_mutex);
> +	if (bridge->hpd_cb)
> +		bridge->hpd_cb(bridge->hpd_data, status);
> +	mutex_unlock(&bridge->hpd_mutex);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
> +
>  #ifdef CONFIG_OF
>  /**
>   * of_drm_find_bridge - find the bridge corresponding to the device node in
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 7616f6562fe4..7db6ca0fd75d 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -23,14 +23,16 @@
>  #ifndef __DRM_BRIDGE_H__
>  #define __DRM_BRIDGE_H__
>  
> -#include <linux/list.h>
>  #include <linux/ctype.h>
> +#include <linux/list.h>
> +#include <linux/mutex.h>
>  #include <drm/drm_mode_object.h>
>  #include <drm/drm_modes.h>
>  
>  struct drm_bridge;
>  struct drm_bridge_timings;
>  struct drm_panel;
> +struct i2c_adapter;
>  
>  /**
>   * struct drm_bridge_funcs - drm_bridge control functions
> @@ -334,6 +336,111 @@ struct drm_bridge_funcs {
>  	 */
>  	void (*atomic_post_disable)(struct drm_bridge *bridge,
>  				    struct drm_atomic_state *state);
> +
> +	/**
> +	 * @detect:
> +	 *
> +	 * Check if anything is attached to the bridge output.
> +	 *
> +	 * This callback is optional, if not implemented the bridge will be
> +	 * considered as always having a component attached to its output.
> +	 * Bridges that implement this callback shall set the
> +	 * DRM_BRIDGE_OP_DETECT flag in their &drm_bridge->ops.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * drm_connector_status indicating the bridge output status.
> +	 */
> +	enum drm_connector_status (*detect)(struct drm_bridge *bridge);
> +
> +	/**
> +	 * @get_modes:
> +	 *
> +	 * Fill all modes currently valid for the sink into the &drm_connector
> +	 * with drm_mode_probed_add().
> +	 *
> +	 * The @get_modes callback is mostly intended to support non-probable
> +	 * displays such as many fixed panels. Bridges that support reading
> +	 * EDID shall leave @get_modes unimplemented and implement the
> +	 * &drm_bridge_funcs->get_edid callback instead.
> +	 *
> +	 * This callback is optional. Bridges that implement it shall set the
> +	 * DRM_BRIDGE_OP_MODES flag in their &drm_bridge->ops.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * The number of modes added by calling drm_mode_probed_add().
> +	 */
> +	int (*get_modes)(struct drm_bridge *bridge,
> +			 struct drm_connector *connector);
> +
> +	/**
> +	 * @get_edid:
> +	 *
> +	 * Read and parse the EDID data of the connected display.
> +	 *
> +	 * The @get_edid callback is the preferred way of reporting mode
> +	 * information for a display connected to the bridge output. Bridges
> +	 * that support readind EDID shall implement this callback and leave
> +	 * the @get_modes callback unimplemented.
> +	 *
> +	 * The caller of this operation shall first verify the output
> +	 * connection status and refrain from reading EDID from a disconnected
> +	 * output.
> +	 *
> +	 * This callback is optional. Bridges that implement it shall set the
> +	 * DRM_BRIDGE_OP_EDID flag in their &drm_bridge->ops.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * An edid structure newly allocated with kmalloc() (or similar) on
> +	 * success, or NULL otherwise. The caller is responsible for freeing
> +	 * the returned edid structure with kfree().
> +	 */
> +	struct edid *(*get_edid)(struct drm_bridge *bridge,
> +				 struct drm_connector *connector);
> +
> +	/**
> +	 * @hpd_notify:
> +	 *
> +	 * Notify the bridge of hot plug detection.
> +	 *
> +	 * This callback is optional, it may be implemented by bridges that
> +	 * need to be notified of display connection or disconnection for
> +	 * internal reasons. One use case is to reset the internal state of CEC
> +	 * controllers for HDMI bridges.
> +	 */
> +	void (*hpd_notify)(struct drm_bridge *bridge,
> +			   enum drm_connector_status status);
> +
> +	/**
> +	 * @hpd_enable:
> +	 *
> +	 * Enable hot plug detection. From now on the bridge shall call
> +	 * drm_bridge_hpd_notify() each time a change is detected in the output
> +	 * connection status, until hot plug detection gets disabled with
> +	 * @hpd_disable.
> +	 *
> +	 * This callback is optional and shall only be implemented by bridges
> +	 * that support hot-plug notification without polling. Bridges that
> +	 * implement it shall also implement the @hpd_disable callback and set
> +	 * the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
> +	 */
> +	void (*hpd_enable)(struct drm_bridge *bridge);
> +
> +	/**
> +	 * @hpd_disable:
> +	 *
> +	 * Disable hot plug detection. Once this function returns the bridge
> +	 * shall not call drm_bridge_hpd_notify() when a change in the output
> +	 * connection status occurs.
> +	 *
> +	 * This callback is optional and shall only be implemented by bridges
> +	 * that support hot-plug notification without polling. Bridges that
> +	 * implement it shall also implement the @hpd_enable callback and set
> +	 * the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
> +	 */
> +	void (*hpd_disable)(struct drm_bridge *bridge);
>  };
>  
>  /**
> @@ -372,6 +479,39 @@ struct drm_bridge_timings {
>  	bool dual_link;
>  };
>  
> +/**
> + * enum drm_bridge_ops - Bitmask of operations supported by the bridge
> + */
> +enum drm_bridge_ops {
> +	/**
> +	 * @DRM_BRIDGE_OP_DETECT: The bridge can detect displays connected to
> +	 * its output. Bridges that set this flag shall implement the
> +	 * &drm_bridge_funcs->detect callback.
> +	 */
> +	DRM_BRIDGE_OP_DETECT = BIT(0),
> +	/**
> +	 * @DRM_BRIDGE_OP_EDID: The bridge can retrieve the EDID of the display
> +	 * connected to its output. Bridges that set this flag shall implement
> +	 * the &drm_bridge_funcs->get_edid callback.
> +	 */
> +	DRM_BRIDGE_OP_EDID = BIT(1),
> +	/**
> +	 * @DRM_BRIDGE_OP_HPD: The bridge can detect hot-plug and hot-unplug
> +	 * without requiring polling. Bridges that set this flag shall
> +	 * implement the &drm_bridge_funcs->hpd_enable and
> +	 * &drm_bridge_funcs->hpd_disable callbacks if they support enabling
> +	 * and disabling hot-plug detection dynamically.
> +	 */
> +	DRM_BRIDGE_OP_HPD = BIT(2),
> +	/**
> +	 * @DRM_BRIDGE_OP_MODES: The bridge can retrieving the modes supported
> +	 * by the display at its output. This does not include readind EDID
> +	 * which is separately covered by @DRM_BRIDGE_OP_EDID. Bridges that set
> +	 * this flag shall implement the &drm_bridge_funcs->get_modes callback.
> +	 */
> +	DRM_BRIDGE_OP_MODES = BIT(3),
> +};
> +
>  /**
>   * struct drm_bridge - central DRM bridge control structure
>   */
> @@ -398,6 +538,33 @@ struct drm_bridge {
>  	const struct drm_bridge_funcs *funcs;
>  	/** @driver_private: pointer to the bridge driver's internal context */
>  	void *driver_private;
> +	/** @ops: bitmask of operations supported by the bridge */
> +	enum drm_bridge_ops ops;
> +	/**
> +	 * @type: Type of the connection at the bridge output
> +	 * (DRM_MODE_CONNECTOR_*). For bridges at the end of this chain this
> +	 * identifies the type of connected display.
> +	 */
> +	int type;
> +	/**
> +	 * @ddc: Associated I2C adapter for DDC access, if any.
> +	 */
> +	struct i2c_adapter *ddc;
> +	/** private: */
> +	/**
> +	 * @hpd_mutex: Protects the @hpd_cb and @hpd_data fields.
> +	 */
> +	struct mutex hpd_mutex;
> +	/**
> +	 * @hpd_cb: Hot plug detection callback, registered with
> +	 * drm_bridge_hpd_enable().
> +	 */
> +	void (*hpd_cb)(void *data, enum drm_connector_status status);
> +	/**
> +	 * @hpd_data: Private data passed to the Hot plug detection callback
> +	 * @hpd_cb.
> +	 */
> +	void *hpd_data;
>  };
>  
>  void drm_bridge_add(struct drm_bridge *bridge);
> @@ -428,6 +595,14 @@ void drm_atomic_bridge_pre_enable(struct drm_bridge *bridge,
>  void drm_atomic_bridge_enable(struct drm_bridge *bridge,
>  			      struct drm_atomic_state *state);
>  
> +void drm_bridge_hpd_enable(struct drm_bridge *bridge,
> +			   void (*cb)(void *data,
> +				      enum drm_connector_status status),
> +			   void *data);
> +void drm_bridge_hpd_disable(struct drm_bridge *bridge);
> +void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> +			   enum drm_connector_status status);
> +
>  #ifdef CONFIG_DRM_PANEL_BRIDGE
>  struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel,
>  					u32 connector_type);

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