Make the Level Meter check compatible with alsa-sim.c

Rather than retrieving the firmware version in alsa_scan_cards(), use
get_elem_by_name() to check if the control is present.

Update alsa-sim.c alsa_config_to_new_elem() to read iface=CARD
controls.

src/alsa-sim.c

@@ -249,12 +249,13 @@ static int alsa_config_to_new_elem(
     }
   }
 
-  // check iface value; only interested in MIXER and PCM
+  // check iface value; only interested in CARD, MIXER, and PCM
   if (!iface) {
     printf("missing iface node in control id %d\n", id);
     goto fail;
   }
-  if (strcmp(iface, "MIXER") != 0 &&
+  if (strcmp(iface, "CARD") != 0 &&
+      strcmp(iface, "MIXER") != 0 &&
       strcmp(iface, "PCM") != 0)
     goto fail;
 

src/alsa.c

@@ -473,14 +473,6 @@ static void alsa_add_card_callback(struct alsa_card *card) {
   );
 }
 
-static void alsa_get_firmware_version(struct alsa_card *card) {
-  struct alsa_elem *elem = get_elem_by_name(card->elems, "Firmware Version");
-
-  if (!elem)
-    return;
-  card->firmware_version = alsa_get_elem_value(elem);
-}
-
 static void alsa_subscribe(struct alsa_card *card) {
   int count = snd_ctl_poll_descriptors_count(card->handle);
 
@@ -535,7 +527,6 @@ void alsa_scan_cards(void) {
     card->handle = ctl;
 
     alsa_get_elem_list(card);
-    alsa_get_firmware_version(card);
     alsa_subscribe(card);
 
     create_card_window(card);

src/alsa.h

@@ -145,7 +145,6 @@ struct alsa_card {
   char               *name;
   snd_ctl_t          *handle;
   struct pollfd       pfd;
-  int                 firmware_version;
   GArray             *elems;
   struct alsa_elem   *sample_capture_elem;
   struct alsa_elem   *level_meter_elem;

src/menu.c

@@ -210,7 +210,10 @@ void add_mixer_action_map(struct alsa_card *card) {
     card
   );
 
-  if (card->firmware_version) {
+  // Hide the levels menu item if there is no "Firmware Version"
+  // control (working kernel support for level meters was added in the
+  // same version as the "Firmware Version" control)
+  if (get_elem_by_name(card->elems, "Firmware Version")) {
     g_action_map_add_action_entries(
       G_ACTION_MAP(card->window_main),
       levels_entries,