Re: [PATCH v5 22/22] sound/usb: Use Media Controller API to share media resources

[Shuah Khan <shuahkh@osg.samsung.com>]

On 03/03/2016 11:21 AM, Mauro Carvalho Chehab wrote:
> Em Wed, 2 Mar 2016 15:57:03 -0700
> Shuah Khan <shuahkh@osg.samsung.com> escreveu:
> 
>> On 03/02/2016 01:41 PM, Dan Carpenter wrote:
>>> On Wed, Mar 02, 2016 at 09:50:31AM -0700, Shuah Khan wrote:
>>>> +	mctl = kzalloc(sizeof(*mctl), GFP_KERNEL);
>>>> +	if (!mctl)
>>>> +		return -ENOMEM;
>>>> +
>>>> +	mctl->media_dev = mdev;
>>>> +	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
>>>> +		intf_type = MEDIA_INTF_T_ALSA_PCM_PLAYBACK;
>>>> +		mctl->media_entity.function = MEDIA_ENT_F_AUDIO_PLAYBACK;
>>>> +		mctl->media_pad.flags = MEDIA_PAD_FL_SOURCE;
>>>> +		mixer_pad = 1;
>>>> +	} else {
>>>> +		intf_type = MEDIA_INTF_T_ALSA_PCM_CAPTURE;
>>>> +		mctl->media_entity.function = MEDIA_ENT_F_AUDIO_CAPTURE;
>>>> +		mctl->media_pad.flags = MEDIA_PAD_FL_SINK;
>>>> +		mixer_pad = 2;
>>>> +	}
>>>> +	mctl->media_entity.name = pcm->name;
>>>> +	media_entity_pads_init(&mctl->media_entity, 1, &mctl->media_pad);
>>>> +	ret =  media_device_register_entity(mctl->media_dev,
>>>> +					    &mctl->media_entity);
>>>> +	if (ret)
>>>> +		goto err1;
>>>
>>> Could we give this label a meaningful name instead of a number?
>>> goto free_mctl;
>>
>> I do see other places where numbered labels are used.
>> Names might help with code readability.
>>
>> register_entity_fail probably makes more sense as a
>> label than free_mctl. In any case, I can address the
>> labels in a follow-on patch.
>>
>>>
>>>> +
>>>> +	mctl->intf_devnode = media_devnode_create(mdev, intf_type, 0,
>>>> +						  MAJOR(pcm_dev->devt),
>>>> +						  MINOR(pcm_dev->devt));
>>>> +	if (!mctl->intf_devnode) {
>>>> +		ret = -ENOMEM;
>>>> +		goto err2;
>>>
>>> goto unregister_device;
>>>
>>>> +	}
>>>> +	mctl->intf_link = media_create_intf_link(&mctl->media_entity,
>>>> +						 &mctl->intf_devnode->intf,
>>>> +						 MEDIA_LNK_FL_ENABLED);
>>>> +	if (!mctl->intf_link) {
>>>> +		ret = -ENOMEM;
>>>> +		goto err3;
>>>
>>> goto delete_devnode;
>>>
>>>> +	}
>>>> +
>>>> +	/* create link between mixer and audio */
>>>> +	media_device_for_each_entity(entity, mdev) {
>>>> +		switch (entity->function) {
>>>> +		case MEDIA_ENT_F_AUDIO_MIXER:
>>>> +			ret = media_create_pad_link(entity, mixer_pad,
>>>> +						    &mctl->media_entity, 0,
>>>> +						    MEDIA_LNK_FL_ENABLED);
>>>> +			if (ret)
>>>> +				goto err4;
>>>
>>> This is a bit weird because we're inside a loop.  Shouldn't we call
>>> media_entity_remove_links() or something if this is the second time
>>> through the loop?
>>
>> Links are removed from media_device_unregister_entity()
>> which is called in the error path.
>>
>>>
>>> I don't understand this.  The kernel has the media_entity_cleanup() stub
>>> function which is supposed to do this but it hasn't been implemented
>>> yet?
>>>
>>
>> Please see above. Links are removed when entity is
>> unregistered. media_entity_cleanup() is a stub. It
>> isn't intended for removing links.
> 
> Shuah,
> 
> Please address the issue that Dan is pointing on a separate
> patch.
> 

Mauro,

Sent it a couple of hours ago. 

https://lkml.org/lkml/2016/3/3/601
https://www.mail-archive.com/linux-media@vger.kernel.org/msg95141.html

thanks,
-- Shuah


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