At Wed, 03 Sep 2014 18:23:49 +0100,
Barry Scott wrote:
>
> It seems that there is a limit of 32 pcm softvol interfaces.
>
> In my test script I loop running speaker-test with a new softvol
> on each run and finally see this after creating 32 pcm softvol.
>
> speaker-test 1.0.27.2
>
> Playback device is default
> Stream parameters are 48000Hz, S16_LE, 1 channels
> Using 16 octaves of pink noise
> ALSA lib pcm_softvol.c:747:(softvol_load_control) Cannot add a control
> Playback open error: -12,Cannot allocate memory
>
> This is the code we use in asound.conf to create the softvol:
>
> pcm.softvol
> {
> type softvol
> slave
> {
> pcm "playback"
> format "S16_LE"
> }
> control
> {
> name
> {
> @func concat
> strings [ "NTB_"
> {
> @func getenv
> vars [ ONELAN_MIXER_SUFFIX ]
> default "Unknown"
> }
> ]
> }
> card "PCH"
> }
> }
>
> pcm.!default
> {
> type plug
> slave.pcm "softvol"
> }
>
>
> I have been reading alsa code and Googling but have not yet found where this
> limit
> is coming from.
>
> Could you point in the right direction please?
It's a restriction in the kernel side. You have to rebuild the kernel
after changing the value MAX_USER_CONTROLS in sound/core/control.c.
Takashi
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