[PATCH v2] udev-detect: warn when a sound card is busy

[tanuk@xxxxxx (Tanu Kaskinen)]

Having a warning in the syslog should make it a bit easier to debug
situations where some other program is hogging the sound card.
---

Changes in v2:
 - Got rid of path_get_card_id() repetition by adding the id variable.
 - More informative log message (includes the alsa card index and a
   suggestion to use lsof).
 - Replaced the separate "if (busy)" and "if (!busy)" checks with an
   if-else structure.

Would someone like to make a patch for actually running the lsof command
and including the output in the log message? I may or may do it myself
at some point, but of course I'd like it if someone else did that for me :)

 src/modules/module-udev-detect.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/modules/module-udev-detect.c b/src/modules/module-udev-detect.c
index d119f96ae..c67789293 100644
--- a/src/modules/module-udev-detect.c
+++ b/src/modules/module-udev-detect.c
@@ -279,6 +279,7 @@ fail:
 }
 
 static void verify_access(struct userdata *u, struct device *d) {
+    const char *id;
     char *cd;
     pa_card *card;
     bool accessible;
@@ -286,7 +287,8 @@ static void verify_access(struct userdata *u, struct device *d) {
     pa_assert(u);
     pa_assert(d);
 
-    cd = pa_sprintf_malloc("/dev/snd/controlC%s", path_get_card_id(d->path));
+    id = path_get_card_id(d->path);
+    cd = pa_sprintf_malloc("/dev/snd/controlC%s", id);
     accessible = access(cd, R_OK|W_OK) >= 0;
     pa_log_debug("%s is accessible: %s", cd, pa_yes_no(accessible));
 
@@ -307,10 +309,13 @@ static void verify_access(struct userdata *u, struct device *d) {
              * device closes it we will get another notification via
              * inotify and can then recheck. */
 
-            busy = is_card_busy(path_get_card_id(d->path));
-            pa_log_debug("%s is busy: %s", d->path, pa_yes_no(busy));
+            busy = is_card_busy(id);
 
-            if (!busy) {
+            if (busy)
+                pa_log_warn(_("Can't use sound card %s (alsa card index: %s), because some other program is using it. "
+                              "This command may be helpful in figuring what program that is: lsof /dev/snd/pcmC%s*"),
+                            d->card_name, id, id);
+            else {
 
                 /* So, why do we rate limit here? It's certainly ugly,
                  * but there seems to be no other way. Problem is
-- 
2.17.0