This patchset is a result of my attempt to fix a bug (https://bugzilla.kernel.org/show_bug.cgi?id=180071) that eventually turned out to be caused by a missing quirk in snd-usb-audio. My idea was to remove the AC97 interface and setup the codec using the same values and in the same order as the Windows driver does, hoping there might be some "magic" sequence that would make the sound work the way it should. Although this didn't help to fix the problem, I found these changes to be useful nevertheless.
IMHO, having all of the AC97 codec's channels exposed to userspace is confusing since most of them have no meaning for this device anyway. Changing these values in alsamixer has either no effect at all or may even reduce the sound quality since it can actually increase the line-in DC offset (slightly). In addition, having to re-select the correct capture channel everytime the device has been plugged in is annoying. At least on my systems the mixer setup is only saved if the device is plugged in during shutdown/reboot. I also get error messages in my kernel log when I unplug the device because some process (probably the AC97 driver) ist trying to read from the device after it has been removed. Either way the device should work out-of-the-box without the need for the user to manually setup channels. The first patch in the set therefore removes the 'stk1160-mixer' and lets the driver setup the AC97 codec using the same values as the Windows driver. Although some of the values seem to be defaults I let the driver set them either way, just to be sure. The second patch adds a check to determine whether the device is strapped to use the internal 8-bit ADC or an external chip. There's currently no check in place to determine whether the device uses AC-link or I2S, but then again I haven't heard of any of these devices actually using an I2S chip. If the device uses the internal ADC the AC97 setup can be skipped. I implemented the check inside stk1160-ac97. It could just as well be in stk1160-core but this way just seemed cleaner. If at some point the need arises to check other power-on strap values, it might make sense to refactor this then. The third patch adds a new module parameter for setting the record gain manually since the AC97 chip is no longer exposed to userspace. The Windows driver doesn't allow this value to be changed but instead always sets it to 8 (of 15). While this should be fine for most users, some may prefer something higher. The fourth patch addresses an issue when reading from the AC97 chip too soon, resulting in corrupt data. Changes from version 2: * Added copyright notice * Added defines for POSVA bytes and bits * Added check for ACDOUT bit to determine whether audio is disabled completely * Removed info output for gain setting * Added fourth patch which had been submitted independently before * Expanded comment on AC97 read delay Marcel Hasler (4): stk1160: Remove stk1160-mixer and setup internal AC97 codec automatically. stk1160: Check whether to use AC97 codec. stk1160: Add module param for setting the record gain. stk1160: Give the chip some time to retrieve data from AC97 codec. drivers/media/usb/stk1160/Kconfig | 10 +- drivers/media/usb/stk1160/Makefile | 4 +- drivers/media/usb/stk1160/stk1160-ac97.c | 159 +++++++++++++++++-------------- drivers/media/usb/stk1160/stk1160-core.c | 8 +- drivers/media/usb/stk1160/stk1160-reg.h | 8 ++ drivers/media/usb/stk1160/stk1160.h | 9 +- 6 files changed, 98 insertions(+), 100 deletions(-) -- 2.10.2 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
