[alsa-devel] How to implement capture_switch control?
Hello list,
I have a device with wm8903 codec. To support mute/unmute capture signal, I was trying to enable/disable PGA on this codec from user space application like
snd_ctl_elem_value_set_boolean("Left Input PGA Switch", 0, 0)
That means the mute/unmute function became platform dependent. I got the idea to support mute/unmute function with enabling/disabling capture switch. However, the function
snd_mixer_selem_has_capture_switch()
alwasy return false. I guess something is missing in my driver. Could you please give some bright how could I use capture switch to mute/unmute a channel. How could I implement capture_switch control properly? Thank you!
/Adam
On Mon, Jun 20, 2011 at 04:15:38PM +0900, Adam Jiang wrote:
I have a device with wm8903 codec. To support mute/unmute capture signal, I was trying to enable/disable PGA on this codec from user space application like
If the hardware does not physically support mute then this should be emulated in software. In the case of the WM8903 the device does not have a specific capture mute control, though extremely low gains are supported for the Capture Volume control which function as a mute so you could also set minimum Capture Volume.
alwasy return false. I guess something is missing in my driver. Could you please give some bright how could I use capture switch to mute/unmute a channel. How could I implement capture_switch control properly? Thank you!
Not all hardware supports all possible features. Either configure a software volume control, the softvol plugin for ALSA should be able to do this, or adjust your application to handle this in the application layer.
http://alsa.opensrc.org/How_to_use_softvol_to_control_the_master_volume
has some information on using softvol.
2011/6/21 Mark Brown broonie@opensource.wolfsonmicro.com:
On Mon, Jun 20, 2011 at 04:15:38PM +0900, Adam Jiang wrote:
I have a device with wm8903 codec. To support mute/unmute capture signal, I was trying to enable/disable PGA on this codec from user space application like
If the hardware does not physically support mute then this should be emulated in software. In the case of the WM8903 the device does not have a specific capture mute control, though extremely low gains are supported for the Capture Volume control which function as a mute so you could also set minimum Capture Volume.
I got the idea about software emulation for mute. Would you please point me to an example about device/driver where hardware capture switch is supported?
alwasy return false. I guess something is missing in my driver. Could you please give some bright how could I use capture switch to mute/unmute a channel. How could I implement capture_switch control properly? Thank you!
Not all hardware supports all possible features. Either configure a software volume control, the softvol plugin for ALSA should be able to do this, or adjust your application to handle this in the application layer.
http://alsa.opensrc.org/How_to_use_softvol_to_control_the_master_volume
has some information on using softvol.
I have solved the problem by enabling/disabling PGA for analog input paths. For digital mic on wm8903, this function could be implemented by turning volume to lowest level for mute, and restore volume level for unmute. Thank you!
On Wed, Jun 22, 2011 at 04:56:26PM +0900, Adam Jiang wrote:
2011/6/21 Mark Brown broonie@opensource.wolfsonmicro.com:
On Mon, Jun 20, 2011 at 04:15:38PM +0900, Adam Jiang wrote:
If the hardware does not physically support mute then this should be emulated in software. ?In the case of the WM8903 the device does not have a specific capture mute control, though extremely low gains are supported for the Capture Volume control which function as a mute so you could also set minimum Capture Volume.
I got the idea about software emulation for mute. Would you please point me to an example about device/driver where hardware capture switch is supported?
grep "Capture Switch" sound/soc/codecs/*.c
2011/6/22 Mark Brown broonie@opensource.wolfsonmicro.com:
On Wed, Jun 22, 2011 at 04:56:26PM +0900, Adam Jiang wrote:
2011/6/21 Mark Brown broonie@opensource.wolfsonmicro.com:
On Mon, Jun 20, 2011 at 04:15:38PM +0900, Adam Jiang wrote:
If the hardware does not physically support mute then this should be emulated in software. ?In the case of the WM8903 the device does not have a specific capture mute control, though extremely low gains are supported for the Capture Volume control which function as a mute so you could also set minimum Capture Volume.
I got the idea about software emulation for mute. Would you please point me to an example about device/driver where hardware capture switch is supported?
grep "Capture Switch" sound/soc/codecs/*.c
I got wm8904 as an example. In the driver of wm8904, there is a control defined as
SOC_DOUBLE_R("Capture Switch", WM8904_ANALOGUE_LEFT_INPUT_0, WM8904_ANALOGUE_RIGHT_INPUT_0, 7, 1, 0),
And, there is also its peer in wm8903 defined as
SOC_SINGLE("Left Input PGA Switch", WM8903_ANALOGUE_LEFT_INPUT_0, 7, 1, 1),
I checked their datasheet and I found there is no difference between the registers of ANALOGUE_LEFT_INPUT_0. Both of them have one bit for mute/unmute analog input path. Comparing SOC_SINGLE and SOC_DOUBLE macro, one snd_soc_control structure is missing in former. What is exactly the difference between the two definitions. Is there any docs to describe how could I use these macros in soc.h?
participants (2)
-
Adam Jiang -
Mark Brown