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

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Date:	Thu, 28 Jan 2016 13:33:00 -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,
	laurent.pinchart@...asonboard.com, sakari.ailus@...ux.intel.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 10:15 AM, Mauro Carvalho Chehab wrote:
> Em Thu, 28 Jan 2016 09:28:37 -0700
> Shuah Khan <shuahkh@....samsung.com> escreveu:
> 
>> 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?
> 
> I'm ok with that for those inlined kernel-doc stuff. On
> the changes at the uapi/linux/media.h, I would prefer if
> you could add the documentation together with the patch,
> as it makes clearer for the reviewers. As you only
> touched it on one or two patches, this won't cause any
> breakages on the remaining patches.
> 

ok I can add documentation to uapi/linux/media.h in the
same patch that adds new defines.

thanks,
-- Shuah


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