Em Mon, 27 Jul 2009 21:36:48 -0300 Mauro Carvalho Chehab <mche...@infradead.org> escreveu:
> Em Mon, 20 Jul 2009 14:00:08 -0400 > ac...@fastmail.fm escreveu: > > > On Sun, Jul 19, 2009 at 10:50:49AM -0300, Mauro Carvalho Chehab wrote: > > > Em Sat, 18 Jul 2009 14:22:51 -0400 > > > ac...@fastmail.fm escreveu: > > > > > > > How do you control the i2s volume output on empia boards? > > > > > > the em28xx chip doesn't control volume. This is done at the audio chip. > > > > > > For ac97 chips, the volume is inside the em28xx driver, since we don't > > > have a > > > v4l2 device driver for it yet. > > > > > > On the cases where the volume is on an i2s chips like msp34xx, the volume > > > control is done at the i2c driver, that should be exporting such controls > > > via > > > v4l2 dev/subdev API, by calling: > > > v4l2_device_call_all(&dev->v4l2_dev, 0, core, s_ctrl, ctrl); > > > > > > This way, any application can control the volume via the proper ioctl's. > > > > > > While trying to see why are you asking this, I noticed that the em28xx > > > driver, > > > due to historic reasons, had an implementation that may cause > > > confusion. > > > > The problem is that it's not working for usb audio streaming. With a > > cable from line out of the device to my sound card it works well. > > Volume can be controlled by applications using the v4l2 ioctls. > > > > The audio from /dev/dsp? is always at max and distorts horribly on > > many tv stations. I can verify with 'modprobe msp3400 debug=1' that > > it is trying to set volume I pass to it, but it simply has no effect > > on the usb audio stream. > > > > The reason I asked about i2s volume control is because the eeprom has > > the bit set that shows my device as "USB audio class volume control > > (capable) when audio source is i2s device". Angelo, I just checked the datasheet, at page 8 [1]: there's nothing we can do at msp34xx to control volume at i2s interface. Looking at the signal flow block diagram of MSP34x5G, it is clear that you have 3 different output patches: 1) loudspeaker: offers bass/treble, loudness, spatial effects, balance and volume controls; 2) SCART1 output: offers only volume control; 3) I2S: no control at all. So, with msp34xx, there's no way to change the i2s output volume. [1] http://www.datasheetcatalog.org/datasheet/MicronasIntermetall/mXsrwrs.pdf Cheers, Mauro -- 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
