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

Shuah Khan
2016-02-26T20:08:49Z

On 02/26/2016 12:55 PM, Takashi Iwai wrote:
> 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)

My current config is MEDIA_SUPPORT=m and SND_USB_AUDIO=y
It is working and I didn't see any issues so far. Maybe
the current change is good. I am hoping kbuild-bot can
find issues (if any) once it gets merged.

>
> 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?

Right. I have been looking into device removal path when
ioctls are active and I can resolve any issues that might
surface while an audio app is active when device is removed.

>
> 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 for the Ack
-- Shuah

>
>
> thanks,
>
> Takashi
>

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