[alsa-devel] [PATCH] Fix codec_dai->ops NULL pointer bug for AC97 codec dai in soc-core

[Barry Song]

AC97 codec DAIs don't register themselves eg.stac9766, wm9712, wm9713, wm9705.c, ad1980,
then it loses to the chance to be given a null_dai_ops in snd_soc_register_dai if they
have no ops. When functions like soc_pcm_open, soc_pcm_hw_params etc. access the ops field
in these DAIs, panic will happen.

Signed-off-by: Barry Song <21cnbao at gmail.com>
---
 sound/soc/soc-core.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index fa0da3c..6643d64 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -795,6 +795,9 @@ static int soc_resume(struct device *dev)
 #define soc_resume	NULL
 #endif
 
+static struct snd_soc_dai_ops null_dai_ops = {
+};
+
 static void snd_soc_instantiate_card(struct snd_soc_card *card)
 {
 	struct platform_device *pdev = container_of(card->dev,
@@ -838,6 +841,12 @@ static void snd_soc_instantiate_card(struct snd_soc_card *card)
 			ac97 = 1;
 	}
 
+	for (i = 0; i < card->num_links; i++) {
+		if (card->dai_link[i].codec_dai->ac97_control &&
+				(!card->dai_link[i].codec_dai->ops))
+			card->dai_link[i].codec_dai->ops = &null_dai_ops;
+	}
+
 	/* If we have AC97 in the system then don't wait for the
 	 * codec.  This will need revisiting if we have to handle
 	 * systems with mixed AC97 and non-AC97 parts.  Only check for
@@ -2332,9 +2341,6 @@ static int snd_soc_unregister_card(struct snd_soc_card *card)
 	return 0;
 }
 
-static struct snd_soc_dai_ops null_dai_ops = {
-};
-
 /**
  * snd_soc_register_dai - Register a DAI with the ASoC core
  *
-- 
1.5.6.3