suse man page for snd_ctl_add_slave

SND_CTL_ADD_SLAVE(9)						 Control/Mixer API					      SND_CTL_ADD_SLAVE(9)

NAME
       snd_ctl_add_slave - Add a virtual slave control

SYNOPSIS
       int snd_ctl_add_slave(struct snd_kcontrol * master, struct snd_kcontrol * slave);

ARGUMENTS
       master
	   vmaster element

       slave
	   slave element to add

DESCRIPTION
       Add a virtual slave control to the given master element created via snd_ctl_create_virtual_master beforehand. Returns zero if successful or
       a negative error code.

       All slaves must be the same type (returning the same information via info callback). The fucntion doesn't check it, so it's your
       responsibility.

       Also, some additional limitations: at most two channels, logarithmic volume control (dB level) thus no linear volume, master can only
       attenuate the volume without gain

COPYRIGHT
Kernel Hackers Manual 2.6.					     July 2010						      SND_CTL_ADD_SLAVE(9)