I did some further tests, and the following program fails without the patch:
#include <sys/ioctl.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/soundcard.h>
int
main(void)
{
int fd;
int format;
int channels;
if ((fd = open("/dev/dsp", O_WRONLY, 0)) == -1) {
perror("open");
return 1;
}
format = AFMT_S16_LE;
if (ioctl(fd, SNDCTL_DSP_SETFMT, &format) == -1) {
perror("SNDCTL_DSP_SETFMT");
return 1;
}
channels = 2;
if (ioctl(fd, SNDCTL_DSP_CHANNELS, &channels) == -1) {
perror("SNDCTL_DSP_CHANNELS");
return 1;
}
return 0;
}
Output:
SNDCTL_DSP_CHANNELS: Device or resource busy
(I admin to having edited the above code slightly in this mail, so I might have
introduced some silly bug, but you get what I mean, just open the device
and request some parameters, and boom: -EBUSY)
Cheers,
Peter