alsactl: fix the check for additional elements

The driver may export only write-only elements. The previous
heuristics code do not handle this use case correctly.
Iterate through all elements and skip the write-only ones.

Fixes: https://github.com/alsa-project/alsa-utils/issues/122
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/alsactl/state.c b/alsactl/state.c
index adbd13f97434781320f3a44f993b9fac3a0e00eb..eea923332ee985a910c6cd49f01b39120f17477a 100644 (file)
--- a/alsactl/state.c
+++ b/alsactl/state.c
@@ -1482,13 +1482,19 @@ static int set_controls(int card, snd_config_t *top, int doit)
 {
        snd_ctl_t *handle;
        snd_ctl_card_info_t *info;
+       snd_ctl_elem_list_t *list;
+       snd_ctl_elem_info_t *elem_info;
+       snd_ctl_elem_id_t *elem_id;
        snd_config_t *control;
        snd_config_iterator_t i, next;
-       int err, maxnumid = -1;
+       int err, maxnumid = -1, maxnumid2 = -1;
+       unsigned int idx, count = 0;
        char name[32], tmpid[16];
        const char *id;
        snd_ctl_card_info_alloca(&info);
-
+       snd_ctl_elem_list_alloca(&list);
+       snd_ctl_elem_info_alloca(&elem_info);
+       snd_ctl_elem_id_alloca(&elem_id);
        sprintf(name, "hw:%d", card);
        dbg("device='%s', doit=%i", name, doit);
        err = snd_ctl_open(&handle, name, 0);
@@ -1528,22 +1534,54 @@ static int set_controls(int card, snd_config_t *top, int doit)
                        goto _close;
        }
 
-       dbg("maxnumid=%i", maxnumid);
+       if (doit)
+               goto _close;
+
+       err = snd_ctl_elem_list(handle, list);
+       if (err < 0) {
+               error("Cannot determine controls: %s", snd_strerror(err));
+               goto _close;
+       }
+       count = snd_ctl_elem_list_get_count(list);
+       dbg("list count: %u", count);
+       if (count == 0)
+               goto _check;
+       snd_ctl_elem_list_set_offset(list, 0);
+       if (snd_ctl_elem_list_alloc_space(list, count) < 0) {
+               error("No enough memory...");
+               goto _close;
+       }
+       if ((err = snd_ctl_elem_list(handle, list)) < 0) {
+               error("Cannot determine controls (2): %s", snd_strerror(err));
+               goto _free;
+       }
+       maxnumid2 = 0;
+       /* skip non-readable elements */
+       for (idx = 0; idx < count; ++idx) {
+               snd_ctl_elem_info_clear(elem_info);
+               snd_ctl_elem_list_get_id(list, idx, elem_id);
+               snd_ctl_elem_info_set_id(elem_info, elem_id);
+               if (snd_ctl_elem_info(handle, elem_info) == 0) {
+                       if (!snd_ctl_elem_info_is_readable(elem_info))
+                               continue;
+                       maxnumid2++;
+               }
+       }
+
        /* check if we have additional controls in driver */
        /* in this case we should go through init procedure */
-       if (!doit && maxnumid >= 0) {
-               snd_ctl_elem_info_t *info;
-               snd_ctl_elem_info_alloca(&info);
-               snd_ctl_elem_info_set_numid(info, maxnumid+1);
-               if (snd_ctl_elem_info(handle, info) == 0) {
-                       /* not very informative */
-                       /* but value is used for check only */
-                       err = -EAGAIN;
-                       dbg("more controls than maxnumid?");
-                       goto _close;
-               }
+ _check:
+       dbg("maxnumid=%i maxnumid2=%i", maxnumid, maxnumid2);
+       if (maxnumid >= 0 && maxnumid != maxnumid2) {
+               /* not very informative */
+               /* but value is used for check only */
+               err = -EAGAIN;
+               dbg("more controls than maxnumid?");
        }
 
+ _free:
+       if (count >= 0)
+               snd_ctl_elem_list_free_space(list);
  _close:
        snd_ctl_close(handle);
        dbg("result code: %i", err);