ASoC: snd_soc_dai_ops trigger function description

Add a comment to the trigger function in snd_soc_dai_ops struct about
possible command sequences.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/sound/soc-dai.h b/include/sound/soc-dai.h
index ae9a227d35d3..0f2e5daa1451 100644
--- a/include/sound/soc-dai.h
+++ b/include/sound/soc-dai.h
@@ -166,6 +166,13 @@ struct snd_soc_dai_ops {
                 struct snd_soc_dai *);
         int (*prepare)(struct snd_pcm_substream *,
                 struct snd_soc_dai *);
+        /*
+         * NOTE: Commands passed to the trigger function are not necessarily
+         * compatible with the current state of the dai. For example this
+         * sequence of commands is possible: START STOP STOP.
+         * So do not unconditionally use refcounting functions in the trigger
+         * function, e.g. clk_enable/disable.
+         */
         int (*trigger)(struct snd_pcm_substream *, int,
                 struct snd_soc_dai *);
         int (*bespoke_trigger)(struct snd_pcm_substream *, int,