A small program to check logical contradiction between member count and dimension info.

alsa-ctl-dimen-check.c

#include <stdio.h>
#include <stdlib.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <sys/ioctl.h>

#include <unistd.h>

#include <string.h>
#include <errno.h>

#include <sound/asound.h>

static const char *const elem_iface_labels[] = {
	[SNDRV_CTL_ELEM_IFACE_CARD]	= "card",
	[SNDRV_CTL_ELEM_IFACE_HWDEP]	= "hwdep",
	[SNDRV_CTL_ELEM_IFACE_MIXER]	= "mixer",
	[SNDRV_CTL_ELEM_IFACE_PCM]	= "pcm",
	[SNDRV_CTL_ELEM_IFACE_RAWMIDI]	= "rawmidi",
	[SNDRV_CTL_ELEM_IFACE_TIMER]	= "timer",
	[SNDRV_CTL_ELEM_IFACE_SEQUENCER] = "sequencer",
};

static const char *const elem_type_labels[] = {
	[SNDRV_CTL_ELEM_TYPE_BOOLEAN]	= "boolean",
	[SNDRV_CTL_ELEM_TYPE_INTEGER]	= "integer",
	[SNDRV_CTL_ELEM_TYPE_ENUMERATED] = "enumerated",
	[SNDRV_CTL_ELEM_TYPE_BYTES]	= "bytes",
	[SNDRV_CTL_ELEM_TYPE_IEC958]	= "iec60958",
	[SNDRV_CTL_ELEM_TYPE_INTEGER64]	= "integer64",
};

static void dump_elem_info(struct snd_ctl_elem_info *info)
{
	unsigned int cols;
	int i;

	printf("numid: %u\n", info->id.numid);
	printf("  iface: %s\n", elem_iface_labels[info->id.iface]);
	printf("  device: %u\n", info->id.device);
	printf("  subdevice: %u\n", info->id.subdevice);
	printf("  name: %s\n", info->id.name);
	printf("  index: %u\n", info->id.index);

	printf("  type: %s\n", elem_type_labels[info->type]);

	printf("  count: %u\n", info->count);

	if (info->dimen.d[0] > 0) {
		printf("  dimension:\n");
		for (i = 0;
		     i < sizeof(info->dimen.d) / sizeof(info->dimen.d[0]);
		     ++i) {
			cols = info->dimen.d[i];
			if (cols == 0)
				continue;

			printf("    %d: %u %u\n", i, cols, info->count / cols);
			info->count /= cols;
		}
	}
}

static int enumerate_elems(int fd, struct snd_ctl_elem_id *ids,
			   unsigned int count)
{
	struct snd_ctl_elem_info info;
	int i;

	for (i = 0; i < count; ++i) {
		memset(&info, 0, sizeof(info));
		info.id = ids[i];
		if (ioctl(fd, SNDRV_CTL_IOCTL_ELEM_INFO, &info) < 0) {
			printf("ioctl(2) with ELEM_INFO: %s\n",
			       strerror(errno));
			return -errno;
		}

		dump_elem_info(&info);
	}

	return 0;
}

static int list_elems(int fd)
{
	struct snd_ctl_elem_list list = {0};
	int err = 0;

	if (ioctl(fd, SNDRV_CTL_IOCTL_ELEM_LIST, &list) < 0) {
		printf("ioctl(2) with ELEM_LIST: %s\n", strerror(errno));
		return -errno;
	}

	list.pids = calloc(list.count, sizeof(*list.pids));
	if (list.pids == NULL) {
		printf("calloc(3): %s\n", strerror(errno));
		return -ENOMEM;
	}
	list.space = list.count;

	if (ioctl(fd, SNDRV_CTL_IOCTL_ELEM_LIST, &list) < 0) {
		printf("ioctl(2) with ELEM_LIST: %s\n", strerror(errno));
		err = -errno;
		goto end;
	}

	err = enumerate_elems(fd, list.pids, list.count);
end:
	free(list.pids);
	return err;
}

int main(int argc, const char *argv[])
{
	const char *path;
	int fd;
	int err;

	if (argc == 1) {
		printf("At least, one argument is required for a path of "
		       "special file for ALSA control character device.\n");
		return EXIT_FAILURE;
	}
	path = argv[1];

	fd = open(path, O_RDONLY);
	if (fd < 0) {
		printf("open(2): %s\n", strerror(errno));
		return EXIT_FAILURE;
	}

	err = list_elems(fd);
end:
	close(fd);

	if (err < 0)
		return EXIT_FAILURE;

	return EXIT_SUCCESS;
}