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

From: Shuah Khan
Date: Thu Mar 03 2016 - 14:06:53 EST


On 03/03/2016 11:21 AM, Mauro Carvalho Chehab wrote:
> Em Wed, 2 Mar 2016 15:57:03 -0700
> Shuah Khan <shuahkh@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx/msg95141.html

thanks,
-- Shuah


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