control: complement comment for subscribe API

When minus value is given as a parameter, the API returns whether
the caller has already subscribed or not.

This commit adds a comment about this so as better documentation.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/src/control/control.c b/src/control/control.c
index dd428a1501b474405996fdeb2e2cbbef92731ceb..4a28cf6ea7c677d392e00eea3a4fd39f54978e5c 100644 (file)
--- a/src/control/control.c
+++ b/src/control/control.c
@@ -213,7 +213,7 @@ int snd_ctl_poll_descriptors_revents(snd_ctl_t *ctl, struct pollfd *pfds, unsign
 /**
  * \brief Ask to be informed about events (poll, #snd_async_add_ctl_handler, #snd_ctl_read)
  * \param ctl CTL handle
- * \param subscribe 0 = unsubscribe, 1 = subscribe
+ * \param subscribe 0 = unsubscribe, 1 = subscribe, -1 = check subscribe or not
  * \return 0 on success otherwise a negative error code
  */
 int snd_ctl_subscribe_events(snd_ctl_t *ctl, int subscribe)