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

Takashi Iwai
2016-02-26T19:55:34Z

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@osg.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@suse.de>

thanks,

Takashi