Douglas borrowed me a couple devices some time ago. I've made some patches for the first one, but never had time to look at the second device, until this weekend, when I re-discovered it: An em2861-based device: a Kworld 305.
On em2861, the audio interface is provided by a separate device, breaking the audio detection rules.
With this device in hands, and using xawtv with audio support, I decided to make it work.
This patch series contains: - a few em28xx driver random fixes; - support for compiling em28xx driver without IR support; - Mixer control for em28xx-based devices with AC97 mixer; - Add support for the USB vendor audio class at interface 1.
Most em28xx hardware comes with an AC97 mixer (in general, emp202, also manufactured by Empiatech). In general, different types of input (TV, Svideo, Composite) uses different audio inputs at the mixer. Some devices also provide two different outputs (one for the audio out plug, and another for DMA transfers). Each vendor has its own way to connect the device.
The em28xx cards contain the logic to mute/unmute the entries associated with each input, so the direct access to the mixer is interesting only if someone wants to do things like using more than one entry at the same time, or controlling the volume for whatever reason.
With this setup, pulseaudio does the wrong thing: it just assumes that the master volume controls the device. On all tree devices I used for tests, this volume doesn't control the PCM output.
I think that, on one of them, the Master is used to control the Audio Out jack output (seldomly used, on an usb device).
Anyway, this is something that needs to be solved at pulseaudio, not inside the kernel (or, at least, I dunno any way for a driver to tell pulseaudio to not try to mask the audio controls).
Mauro Carvalho Chehab (11): [media] em28xx: Don't initialize a var if won't be using it [media] em28xx: Fix a wrong enum at the ac97 control tables [media] em28xx: Allow to compile it without RC/input support [media] em28xx-alsa: add mixer support for AC97 volume controls [media] em28xx-audio: add support for mute controls [media] em28xx-audio: volumes are inverted [media] em28xx-audio: add debug info for the volume control [media] em28xx-audio: Properly report failures to start stream [media] em28xx-audio: Some Alsa API fixes [media] em28xx: Add support for devices with a separate audio interface [media] em28xx: Mark Kworld 305 as validated
drivers/media/video/em28xx/Kconfig | 10 +- drivers/media/video/em28xx/Makefile | 6 +- drivers/media/video/em28xx/em28xx-audio.c | 253 ++++++++++++++++++++++++++--- drivers/media/video/em28xx/em28xx-cards.c | 104 +++++++++---- drivers/media/video/em28xx/em28xx-core.c | 37 +++-- drivers/media/video/em28xx/em28xx-i2c.c | 2 - drivers/media/video/em28xx/em28xx.h | 20 +++ 7 files changed, 355 insertions(+), 77 deletions(-)