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spa/alsa-udev: fix /proc/asound handling without CONFIG_SND_VERBOSE_PROCFS

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For kernels compiled with CONFIG_SND_VERBOSE_PROCFS=n, the pcmXX
/proc/asound entries do not exist.  In that case, the "device busy"
check cannot be done, but we should still check existence of PCM devices
correctly.

Count the number of PCM devices from /dev/snd, which should work also
without /proc/asound or /sysfs/class/sound.
This commit is contained in:
Pauli Virtanen 2022-02-03 19:23:23 +02:00 committed by Wim Taymans
parent ae077a4967
commit 97a5fe80c1
1 changed files with 73 additions and 15 deletions
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88
spa/plugins/alsa/alsa-udev.c
View file

@ -246,6 +246,60 @@ static void unescape(const char *src, char *dst)
*d = 0;
}
static int check_device_pcm_class(const char *devname)
{
FILE *f;
char path[PATH_MAX];
char buf[16];
size_t sz;
/* Check device class */
spa_scnprintf(path, sizeof(path), "/sys/class/sound/%s/pcm_class",
devname);
f = fopen(path, "r");
if (f == NULL)
return -errno;
sz = fread(buf, 1, sizeof(buf) - 1, f);
buf[sz] = '\0';
fclose(f);
return spa_strstartswith(buf, "modem") ? -ENXIO : 0;
}
static int get_num_pcm_devices(unsigned int card_id)
{
char prefix[32];
DIR *snd = NULL;
struct dirent *entry;
int num_dev = 0;
int res;
/* Check if card has PCM devices, without opening them */
spa_scnprintf(prefix, sizeof(prefix), "pcmC%uD", card_id);
if ((snd = opendir("/dev/snd")) == NULL)
return -errno;
while ((errno = 0, entry = readdir(snd)) != NULL) {
if (!(entry->d_type == DT_CHR &&
spa_strstartswith(entry->d_name, prefix)))
continue;
res = check_device_pcm_class(entry->d_name);
if (res == 0 || res == -ENOENT) {
/* count device also if sysfs status file not there */
++num_dev;
}
}
if (errno != 0)
res = -errno;
else
res = num_dev;
closedir(snd);
return res;
}
static int check_device_available(struct impl *this, struct device *device, int *num_pcm)
{
char path[PATH_MAX];
@ -256,14 +310,26 @@ static int check_device_available(struct impl *this, struct device *device, int
struct dirent *entry, *entry_pcm;
int res;
res = get_num_pcm_devices(device->id);
if (res < 0) {
spa_log_error(this->log, "Error finding PCM devices for ALSA card %u: %s",
(unsigned int)device->id, spa_strerror(res));
return res;
}
*num_pcm = res;
spa_log_debug(this->log, "card %u has %d pcm device(s)", (unsigned int)device->id, *num_pcm);
/*
* Check if some pcm devices of the card are busy. Check it via /proc, as we
* don't want to actually open any devices using alsa-lib (generates uncontrolled
* number of inotify events), or replicate its subdevice logic.
*
* The pcmXX directories do not exist if kernel is compiled with
* CONFIG_SND_VERBOSE_PROCFS=n. In that case, the busy check always
* succeeds.
*/
*num_pcm = 0;
spa_scnprintf(path, sizeof(path), "/proc/asound/card%u", (unsigned int)device->id);
if ((card = opendir(path)) == NULL)
@ -274,16 +340,9 @@ static int check_device_available(struct impl *this, struct device *device, int
spa_strstartswith(entry->d_name, "pcm")))
continue;
/* Check device class */
spa_scnprintf(path, sizeof(path), "/sys/class/sound/pcmC%uD%s/pcm_class",
spa_scnprintf(path, sizeof(path), "pcmC%uD%s",
(unsigned int)device->id, entry->d_name+3);
f = fopen(path, "r");
if (f == NULL)
goto done;
sz = fread(buf, 1, sizeof(buf) - 1, f);
buf[sz] = '\0';
fclose(f);
if (spa_strstartswith(buf, "modem"))
if (check_device_pcm_class(path) < 0)
continue;
/* Check busy status */
@ -319,8 +378,6 @@ static int check_device_available(struct impl *this, struct device *device, int
if (errno != 0)
goto done;
++*num_pcm;
closedir(pcm);
pcm = NULL;
}
@ -352,15 +409,16 @@ static int emit_object_info(struct impl *this, struct device *device)
* device->emitted to true. alsalib functions can be used after that.
*/
snprintf(path, sizeof(path), "hw:%u", id);
if ((res = check_device_available(this, device, &pcm)) < 0)
return res;
if (pcm == 0) {
spa_log_debug(this->log, "no pcm devices for %s", path);
device->ignored = true;
return 0;
return -ENODEV;
}
snprintf(path, sizeof(path), "hw:%u", id);
spa_log_debug(this->log, "emitting card %s", path);
device->emitted = true;