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

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Date:	Thu, 3 Mar 2016 15:21:52 -0300
From:	Mauro Carvalho Chehab <mchehab@....samsung.com>
To:	Shuah Khan <shuahkh@....samsung.com>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>, tiwai@...e.com,
	clemens@...isch.de, hans.verkuil@...co.com,
	laurent.pinchart@...asonboard.com, sakari.ailus@...ux.intel.com,
	javier@....samsung.com, pawel@...iak.com, m.szyprowski@...sung.com,
	kyungmin.park@...sung.com, perex@...ex.cz, arnd@...db.de,
	tvboxspy@...il.com, crope@....fi, ruchandani.tina@...il.com,
	corbet@....net, chehabrafael@...il.com, k.kozlowski@...sung.com,
	stefanr@...6.in-berlin.de, inki.dae@...sung.com,
	jh1009.sung@...sung.com, elfring@...rs.sourceforge.net,
	prabhakar.csengg@...il.com, sw0312.kim@...sung.com,
	p.zabel@...gutronix.de, ricardo.ribalda@...il.com,
	labbott@...oraproject.org, pierre-louis.bossart@...ux.intel.com,
	ricard.wanderlof@...s.com, julian@...st.de, takamichiho@...il.com,
	dominic.sacre@....de, misterpib@...il.com, daniel@...que.org,
	gtmkramer@...all.nl, normalperson@...t.net, joe@...po.co.uk,
	linuxbugs@...tgam.net, johan@...ud.se, klock.android@...il.com,
	nenggun.kim@...sung.com, j.anaszewski@...sung.com,
	geliangtang@....com, albert@...tsing.nl,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	alsa-devel@...a-project.org
Subject: Re: [PATCH v5 22/22] sound/usb: Use Media Controller API to share
 media resources

Em Wed, 2 Mar 2016 15:57:03 -0700
Shuah Khan <shuahkh@....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.

Thanks,
Mauro