linux-kernel - Re: [PATCH 04/31] media: Media Controller enable/disable source handler API

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Message-ID: <56AA41B5.1080703@osg.samsung.com>
Date:	Thu, 28 Jan 2016 09:28:37 -0700
From:	Shuah Khan <shuahkh@....samsung.com>
To:	Mauro Carvalho Chehab <mchehab@....samsung.com>
Cc:	tiwai@...e.com, clemens@...isch.de, hans.verkuil@...co.com,
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	johan@...ud.se, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, linux-api@...r.kernel.org,
	alsa-devel@...a-project.org, Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH 04/31] media: Media Controller enable/disable source
 handler API

On 01/28/2016 08:19 AM, Mauro Carvalho Chehab wrote:
> Em Wed,  6 Jan 2016 13:26:53 -0700
> Shuah Khan <shuahkh@....samsung.com> escreveu:
> 
>> 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 need to run these handlers. The enable_source handler
>> finds source entity for the passed in entity and check if it is
>> available, and activate the link using __media_entity_setup_link()
>> interface. Bridge driver is expected to implement and set these
>> handlers and private data when media_device is registered or when
>> bridge driver finds the media_device during probe. This is to enable
>> the use-case to find tuner entity connected to the decoder entity and
>> check if it is available, and activate it and start pipeline between
>> the source and the entity. The disable_source handler deactivates the
>> link and stops the pipeline. This handler can be invoked from the
>> media core (v4l-core, dvb-core) as well as other drivers such as ALSA
>> that control the media device.
>>
>> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
>> ---
>>  include/media/media-device.h | 19 +++++++++++++++++++
>>  1 file changed, 19 insertions(+)
>>
>> diff --git a/include/media/media-device.h b/include/media/media-device.h
>> index 6520d1c..04b6c2e 100644
>> --- a/include/media/media-device.h
>> +++ b/include/media/media-device.h
>> @@ -333,6 +333,25 @@ struct media_device {
>>  	/* Serializes graph operations. */
>>  	struct mutex graph_mutex;
>>  
>> +	/* Handlers to find source entity for the sink entity and
>> +	 * check if it is available, and activate the link using
>> +	 * media_entity_setup_link() interface and start pipeline
>> +	 * from the source to the entity.
>> +	 * 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
>> +	 * using media_entity_setup_link() if it is available.
>> +	*/
>> +	void *source_priv;
>> +	int (*enable_source)(struct media_entity *entity,
>> +			     struct media_pipeline *pipe);
>> +	void (*disable_source)(struct media_entity *entity);
> 
> Please document the new fields at the right place (Kernel-doc
> comment declared before the struct).
> 
> Is this used by the media core? If so, please but the implementation
> here, to make it clearer why we need those things.
> 
>> +
>>  	int (*link_notify)(struct media_link *link, u32 flags,
>>  			   unsigned int notification);
>>  };

Hi Mauro,

I don't have any problems adding documentation. I would
like to add documentation in a add-on to the patch series.
The main reason is once I add documentation to this patch,
the rest of the patches on this file don't apply and require
rebase and rework. I went though a couple of rounds of this
while you were adding documentation to the interfaces you
added.

How about I add the documentation patches at the end of
the patch series? I am concerned that rebasing for the
documentation changes will introduce bugs. Are you okay
with this proposal?

thanks,
-- Shuah

-- 
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@....samsung.com | (970) 217-8978