control: enhance doc for snd_ctl_ascii_value_parse() function

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/src/control/ctlparse.c b/src/control/ctlparse.c
index c442c44c0535cc08f6207f46b07d75d386d865e7..978977dbc3db4f1b6934a87331186d434c6d1bbb 100644 (file)
--- a/src/control/ctlparse.c
+++ b/src/control/ctlparse.c
@@ -302,6 +302,9 @@ static int get_ctl_enum_item_index(snd_ctl_t *handle,
  * \param info CTL element info structure
  * \param value source ASCII string
  * \return zero on success, otherwise a negative error code
+ *
+ * Note: For toggle command, the dst must contain previous (current)
+ * state (do the #snd_ctl_elem_read call to obtain it).
  */
 int snd_ctl_ascii_value_parse(snd_ctl_t *handle,
                              snd_ctl_elem_value_t *dst,