/* sb16agc - enable/disable AGC on Soundblaster 16
 * PD by RJM 96/1/5
 *
 * compile with 'cc -o sb16agc sb16agc.c'
 * install with 'install -o root -m 4511 sb16agc /usr/local/bin'
 *
 * THIS IS A REVOLTING HACK!
 * (Based on dosemu debug output from 'sb16set /agc:-')
 * DO NOT USE THIS *UNLESS*:
 * - you have a Soundblaster 16; and
 * - 'cat /dev/sndstat' says "SoundBlaster16 at 0x220 ..."
 *	(or in newer kernels, "Sound Blaster at 0x220 ...")
 *
 * Even then, I should add a disclaimer. This program works fine for
 * me, but don't hold me responsible if your machine explodes. :-)
 *
 * Note that this only affects the mic socket - line-in is always
 * free of AGC interference (not to mention being stereo rather than
 * the mic socket's mono).
 */

#include <stdio.h>
#include <unistd.h>


static void inline outb(char value, unsigned short port)
{
__asm__ volatile ("outb %0,%1"
  ::"a" ((char) value),"d" ((unsigned short) port));
}


void die(char *str)
{
fprintf(stderr,"Couldn't %s.\n",str);
}


void usage()
{
printf("usage: sb16agc [on|off]\n");
exit(1);
}


int main(int argc,char *argv[])
{
int disable=0;

if(ioperm(0x224,2,1)==-1) die("get I/O permissions (not setuid root?)");

if(argc!=2) usage(),exit(1);

if(strcmp(argv[1],"on")==0)
  disable=0;
else
  if(strcmp(argv[1],"off")==0)
    disable=1;
  else
    usage(),exit(1);

outb(0x43,0x224);
usleep(10000);
outb(disable,0x225);

exit(0);
}