linux-kernel - Re: [PATCH v3 06/22] media: Media Controller enable/disable source handler API

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Date:	Thu, 10 Mar 2016 09:35:00 +0200
From:	Sakari Ailus <sakari.ailus@....fi>
To:	Shuah Khan <shuahkh@....samsung.com>
Cc:	mchehab@....samsung.com, tiwai@...e.com, clemens@...isch.de,
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Subject: Re: [PATCH v3 06/22] media: Media Controller enable/disable source
 handler API

Hi Shuah,

On Thu, Feb 11, 2016 at 04:41:22PM -0700, Shuah Khan wrote:
> Add new fields to struct media_device to add enable_source, and
> disable_source handlers, and source_priv to stash driver private
> data that is used to run these handlers. The enable_source handler
> finds source entity for the passed in entity and checks if it is
> available. When link is found, it activates it. Disable source
> handler deactivates the link.
> 
> Bridge driver is expected to implement and set these handlers.
> 
> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
> ---
>  include/media/media-device.h | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/include/media/media-device.h b/include/media/media-device.h
> index 075a482..1a04644 100644
> --- a/include/media/media-device.h
> +++ b/include/media/media-device.h
> @@ -302,6 +302,11 @@ struct media_entity_notify {
>   * @entity_notify: List of registered entity_notify callbacks
>   * @lock:	Entities list lock
>   * @graph_mutex: Entities graph operation lock
> + *
> + * @source_priv: Driver Private data for enable/disable source handlers
> + * @enable_source: Enable Source Handler function pointer
> + * @disable_source: Disable Source Handler function pointer
> + *
>   * @link_notify: Link state change notification callback
>   *
>   * This structure represents an abstract high-level media device. It allows easy
> @@ -313,6 +318,26 @@ struct media_entity_notify {
>   *
>   * @model is a descriptive model name exported through sysfs. It doesn't have to
>   * be unique.
> + *
> + * @enable_source is a handler to find source entity for the
> + * sink entity  and activate the link between them if source
> + * entity is free. Drivers should call this handler before
> + * accessing the source.
> + *
> + * @disable_source is a handler to find source entity for the
> + * sink entity  and deactivate the link between them. Drivers
> + * should call this handler to release the source.
> + *

Is there a particular reason you're not simply (de)activating the link, but
instead add a new callback?

> + * Note: Bridge driver is expected to implement and set the
> + * handler when media_device is registered or when
> + * bridge driver finds the media_device during probe.
> + * Bridge driver sets source_priv with information
> + * necessary to run enable/disable source handlers.
> + *
> + * Use-case: find tuner entity connected to the decoder
> + * entity and check if it is available, and activate the
> + * the link between them from enable_source and deactivate
> + * from disable_source.
>   */
>  struct media_device {
>  	/* dev->driver_data points to this struct. */
> @@ -344,6 +369,11 @@ struct media_device {
>  	/* Serializes graph operations. */
>  	struct mutex graph_mutex;
>  
> +	void *source_priv;
> +	int (*enable_source)(struct media_entity *entity,
> +			     struct media_pipeline *pipe);
> +	void (*disable_source)(struct media_entity *entity);
> +
>  	int (*link_notify)(struct media_link *link, u32 flags,
>  			   unsigned int notification);
>  };

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@....fi	XMPP: sailus@...iisi.org.uk