Re: [PATCH v2 26/31] sound/usb: Update ALSA driver to use Managed Media Controller API

On Sat, 16 Jan 2016 01:38:27 +0100,
Shuah Khan wrote:

On 01/15/2016 06:38 AM, Takashi Iwai wrote:

quoted

On Thu, 14 Jan 2016 20:52:28 +0100,
Shuah Khan wrote:

quoted

Change ALSA driver to use Managed Media Managed Controller
API to share tuner with DVB and V4L2 drivers that control
AU0828 media device.  Media device is created based on a
newly added field value in the struct snd_usb_audio_quirk.
Using this approach, the media controller API usage can be
added for a specific device. In this patch, Media Controller
API is enabled for AU0828 hw. snd_usb_create_quirk() will
check this new field, if set will create a media device using
media_device_get_devres() interface.

media_device_get_devres() will allocate a new media device
devres or return an existing one, if it finds one.

During probe, media usb driver could have created the media
device devres. It will then initialze (if necessary) and
register the media device if it isn't already initialized
and registered. Media device unregister is done from
usb_audio_disconnect().

During probe, media usb driver could have created the
media device devres. It will then register the media
device if it isn't already registered. Media device
unregister is done from usb_audio_disconnect().

New structure media_ctl is added to group the new
fields to support media entity and links. This new
structure is added to struct snd_usb_substream.

A new entity_notify hook and a new ALSA capture media
entity are registered from snd_usb_pcm_open() after
setting up hardware information for the PCM device.

When a new entity is registered, Media Controller API
interface media_device_register_entity() invokes all
registered entity_notify hooks for the media device.
ALSA entity_notify hook parses all the entity list to
find a link from decoder it ALSA entity. This indicates
that the bridge driver created a link from decoder to
ALSA capture entity.

ALSA will attempt to enable the tuner to link the tuner
to the decoder calling enable_source handler if one is
provided by the bridge driver prior to starting Media
pipeline from snd_usb_hw_params(). If enable_source returns
with tuner busy condition, then snd_usb_hw_params() will fail
with -EBUSY. Media pipeline is stopped from snd_usb_hw_free().

Signed-off-by: Shuah Khan <redacted>
---
Changes since v1: Addressed Takasi Iwai's comments on v1
- Move config defines to Kconfig and add logic
  to Makefile to conditionally compile media.c
- Removed extra includes from media.c
- Added snd_usb_autosuspend() in error leg
- Removed debug related code that was missed in v1

 sound/usb/Kconfig        |   7 ++
 sound/usb/Makefile       |   4 +
 sound/usb/card.c         |   7 ++
 sound/usb/card.h         |   1 +
 sound/usb/media.c        | 190 +++++++++++++++++++++++++++++++++++++++++++++++
 sound/usb/media.h        |  56 ++++++++++++++
 sound/usb/pcm.c          |  28 +++++--
 sound/usb/quirks-table.h |   1 +
 sound/usb/quirks.c       |   5 ++
 sound/usb/stream.c       |   2 +
 sound/usb/usbaudio.h     |   1 +
 11 files changed, 297 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..8d5cdab 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 || MEDIA_SUPPORT_MODULE)

This looks wrong as a Kconfig syntax.  "... if MEDIA_CONTROLLER"
should work, I suppose?

The conditional select syntax is used in several Kconfig
files. You are right about (MEDIA_SUPPORT || MEDIA_SUPPORT_MODULE)
Adding checks for that is unnecessary.

Well, my point was that check should be like:
   select SND_USB_AUDIO_XXX if MEDIA_CONTROLLER && MEDIA_SUPPORT

as there is no MEDIA_SUPPORT_MODULE in Kconfig.  It's
MEDIA_SUPPORT=m in Kconfig syntax.  In C code, it's
CONFIG_MEDIA_SUPPORT_MODULE, though.

There is a revere-select, so this menu itself doesn't play any role.

If you want this item selectable, drop select from SND_USB_AUDIO but
just have proper dependencies for this item:

config SND_USB_AUDIO_USE_MEDIA_CONTROLLER
	bool "USB Audio/MIDI driver with Media Controller Support"
	depends on SND_USB_AUDIO
	depends on MEDIA_CONTROLLER
	default y

(Whether default y or not is a remaining question: usually we keep it 
 empty (i.e. no), but I put it here since you had it.)

If you want this auto-selected unconditionally, drop the prompt and
superfluous dependency (and don't set default y):

config SND_USB_AUDIO
	....
	select SND_USB_AUDIO_USE_MEDIA_CONTROLLER if MEDIA_CONTROLLER
	....

config SND_USB_AUDIO_USE_MEDIA_CONTROLLER
	bool


Takashi