linux-kernel - Re: [PATCH v3 22/22] sound/usb: Use Media Controller API to share media resources

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Date:	Fri, 26 Feb 2016 20:55:23 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	"Shuah Khan" <shuahkh@....samsung.com>
Cc:	<hans.verkuil@...co.com>, <laurent.pinchart@...asonboard.com>,
	<clemens@...isch.de>, <sakari.ailus@...ux.intel.com>,
	<javier@....samsung.com>, <mchehab@....samsung.com>,
	<geliangtang@....com>, <alsa-devel@...a-project.org>,
	<arnd@...db.de>, <ricard.wanderlof@...s.com>,
	<labbott@...oraproject.org>, <chehabrafael@...il.com>,
	<klock.android@...il.com>, <misterpib@...il.com>,
	<prabhakar.csengg@...il.com>, <ricardo.ribalda@...il.com>,
	<ruchandani.tina@...il.com>, <takamichiho@...il.com>,
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	<pierre-louis.bossart@...ux.intel.com>, <corbet@....net>,
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	<stefanr@...6.in-berlin.de>, <inki.dae@...sung.com>,
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	<k.kozlowski@...sung.com>, <kyungmin.park@...sung.com>,
	<m.szyprowski@...sung.com>, <nenggun.kim@...sung.com>,
	<sw0312.kim@...sung.com>, <elfring@...rs.sourceforge.net>,
	<linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
	<linuxbugs@...tgam.net>, <gtmkramer@...all.nl>,
	<normalperson@...t.net>, <daniel@...que.org>
Subject: Re: [PATCH v3 22/22] sound/usb: Use Media Controller API to share media resources

On Fri, 12 Feb 2016 00:41:38 +0100,
Shuah Khan wrote:
> 
> Change ALSA driver to use Media Controller API to
> share media resources with DVB and V4L2 drivers
> on a AU0828 media device. Media Controller specific
> initialization is done after sound card is registered.
> ALSA creates Media interface and entity function graph
> nodes for Control, Mixer, PCM Playback, and PCM Capture
> devices.
> 
> snd_usb_hw_params() will call Media Controller enable
> source handler interface to request the media resource.
> If resource request is granted, it will release it from
> snd_usb_hw_free(). If resource is busy, -EBUSY is returned.
> 
> Media specific cleanup is done in usb_audio_disconnect().
> 
> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
> ---
>  sound/usb/Kconfig        |   4 +
>  sound/usb/Makefile       |   2 +
>  sound/usb/card.c         |  14 +++
>  sound/usb/card.h         |   3 +
>  sound/usb/media.c        | 318 +++++++++++++++++++++++++++++++++++++++++++++++
>  sound/usb/media.h        |  72 +++++++++++
>  sound/usb/mixer.h        |   3 +
>  sound/usb/pcm.c          |  28 ++++-
>  sound/usb/quirks-table.h |   1 +
>  sound/usb/stream.c       |   2 +
>  sound/usb/usbaudio.h     |   6 +
>  11 files changed, 448 insertions(+), 5 deletions(-)
>  create mode 100644 sound/usb/media.c
>  create mode 100644 sound/usb/media.h
> 
> diff --git a/sound/usb/Kconfig b/sound/usb/Kconfig
> index a452ad7..ba117f5 100644
> --- a/sound/usb/Kconfig
> +++ b/sound/usb/Kconfig
> @@ -15,6 +15,7 @@ config SND_USB_AUDIO
>  	select SND_RAWMIDI
>  	select SND_PCM
>  	select BITREVERSE
> +	select SND_USB_AUDIO_USE_MEDIA_CONTROLLER if MEDIA_CONTROLLER && MEDIA_SUPPORT

Looking at the media Kconfig again, this would be broken if
MEDIA_SUPPORT=m and SND_USB_AUDIO=y.  The ugly workaround is something
like:
	select SND_USB_AUDIO_USE_MEDIA_CONTROLLER \
		if MEDIA_CONTROLLER && (MEDIA_SUPPORT=y || MEDIA_SUPPORT=SND)

Other than that, it looks more or less OK to me.
The way how media_stream_init() gets called is a bit worrisome, but it
should work practically.  Another concern is about the disconnection.
Can all function calls in media_device_delete() be safe even if it's
called while the application still opens the MC device?

In anyway, such a thing can be improved later once after we get this
merged, too.  So, feel fee to take my ack.

 Acked-by: Takashi Iwai <tiwai@...e.de>


thanks,

Takashi