sndstat_enum.c

#include <sys/types.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/nv.h>
#include <sys/sndstat.h>

int
main()
{
	int fd;
	struct sndstat_nvlbuf_arg arg;
	const nvlist_t * const *di;
	size_t i, nitems;
	nvlist_t *nvl;

	/* Open sndstat node in read-only first */
	fd = open("/dev/sndstat", O_RDONLY);

	/* Get the size of snapshot, when nbytes = 0 */
	arg.nbytes = 0;
	arg.buf = NULL;
	ioctl(fd, SNDSTAT_GET_DEVS, &arg);

	/* Get snapshot data */
	arg.buf = malloc(arg.nbytes);
	ioctl(fd, SNDSTAT_GET_DEVS, &arg);

	/* Deserialize the nvlist stream */
	nvl = nvlist_unpack(arg.buf, arg.nbytes, 0);
	free(arg.buf);

	/* Get DSPs array */
	di = nvlist_get_nvlist_array(nvl, SNDSTAT_LABEL_DSPS, &nitems);
	for (i = 0; i < nitems; i++) {
		const char *nameunit, *devnode, *desc;

		/*
		 * Examine each device nvlist item
		 */

		nameunit = nvlist_get_string(di[i], SNDSTAT_LABEL_NAMEUNIT);
		devnode = nvlist_get_string(di[i], SNDSTAT_LABEL_DEVNODE);
		desc = nvlist_get_string(di[i], SNDSTAT_LABEL_DESC);
		printf("Name unit: `%s`, Device node: `%s`, Description: `%s`\n",
		    nameunit, devnode, desc);
	}

	nvlist_destroy(nvl);
	return (0);
}