On Wednesday 12 November 2003 13:03, Christian Esken wrote:
> Hello,
>
> I have a problem with snd_mixer_selem_set_capture_switch_all() from
> alsa-lib. The documentation states:
>
> /**
> * \brief Set value of capture switch control for all channels of a mixer
> simple element
> * \param elem Mixer simple element handle
> * \param value control value
> * \return 0 on success otherwise a negative error code
> */
> int snd_mixer_selem_set_capture_switch_all(snd_mixer_elem_t *elem, int
> value)
>
> So I should receive either 0 or a negative value. But I receive a return
> value of 1. Does anybody know what this means?!? Any help is appreciated
> greatly.
I have investigated and found a possible bug in alsa-lib.
The documentation of snd_mixer_selem_set_capture_switch_all() only mentions
return codes 0 and <0. As I said 1 is returned in my case - I now found a
place where this could happen in the alsa-lib source code. The code is from
src/mixer/simple.c , revision .59.
snd_mixer_selem_set_capture_switch_all() calls selem_write, which calls
selem_read(). At the end of selem_read(), you find the following code
snippet:
if (memcmp(pvol, s->str[PLAY].vol, sizeof(pvol)) ||
psw != s->str[PLAY].sw ||
memcmp(cvol, s->str[CAPT].vol, sizeof(cvol)) ||
csw != s->str[CAPT].sw)
return 1;
This is where 1 is returned. But I do not understand the code. Can anybody
explain to me. It looks a bit like I am passing "bad" parameters, but then I
would expect to be returned an error code like EINVAL.
Greetings,
Chris
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