ASoC: dpcm: improve robustness

Avoid oopsing if there is no backend stream associated with a front end
stream.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index d81b79251760..591f0f3074c5 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1038,6 +1038,12 @@ static int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
                 struct snd_pcm_substream *be_substream =
                         snd_soc_dpcm_get_substream(be, stream);
 
+                if (!be_substream) {
+                        dev_err(be->dev, "ASoC: no backend %s stream\n",
+                                stream ? "capture" : "playback");
+                        continue;
+                }
+
                 /* is this op for this BE ? */
                 if (!snd_soc_dpcm_be_can_update(fe, be, stream))
                         continue;
@@ -1055,7 +1061,8 @@ static int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
                     (be->dpcm[stream].state != SND_SOC_DPCM_STATE_CLOSE))
                         continue;
 
-                dev_dbg(be->dev, "ASoC: open BE %s\n", be->dai_link->name);
+                dev_dbg(be->dev, "ASoC: open %s BE %s\n",
+                        stream ? "capture" : "playback", be->dai_link->name);
 
                 be_substream->runtime = be->dpcm[stream].runtime;
                 err = soc_pcm_open(be_substream);