From: Ron Fox <fox@...>
Date: 2008-03-28T20:35:11+09:00
Subject: Re: accessing mixer values

It encodes the ioctl request argument for a transfer of data from the 
device to the program.  See:
man ioctl

you may also need to look at the ioctl.h header.
_SIOR  in at least the linux soundcard.h file just maps directly to _IOR

RF
ruud wrote:
> hi group
> 
> I want to read the volume of the mixer device with a ruby script.
> Can anybody tell me what the ruby equivalent is of what the MIXER_READ
> macro does in C?
> 
> #define SOUND_MIXER_VOLUME  0
> #define SOUND_MIXER_READ_VOLUME     MIXER_READ(SOUND_MIXER_VOLUME)
> #define MIXER_READ(dev)     _SIOR('M', dev, int)
> 
> I've been googling with keywords like 'ioctl, MIXER_READ SOUND_MIXER',
> but with little result. Hopefully someone can me push me in the right
> direction...
> 
> 
> thanks in advance,
> 
> Ruud