Re: [RFC 0/2] McBSP and ASoC OMAP update patches for 2430 and 34xx

[Felipe Balbi <me@felipebalbi.com>]

On Tue, Aug 26, 2008 at 01:40:06AM +0300, Felipe Balbi wrote:
> On Mon, Aug 25, 2008 at 03:30:13PM -0700, Steve Sakoman wrote:
> > > Hmm, so the crash is actually somewhere else. Could you disable debug
> > > and get the NULL pointer dereference at the right point ?
> > 
> > The output is below.  The crash seems to occur at the substream
> > pointer dereference in the second line of snd_pcm_info (in
> > pcm_native.c):
> > 
> > 	struct snd_pcm *pcm = substream->pcm;
> 
> yeah, at that point substream was NULL. I'm trying to trace the function
> call to see why substream is getting NULLed.
> 
> I think the following patch is anyway a good thing to apply:
> 
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index c49b9d9..c7c15cf 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -92,10 +92,11 @@ static inline void snd_leave_user(mm_segment_t fs)
>  int snd_pcm_info(struct snd_pcm_substream *substream, struct snd_pcm_info *info)
>  {
>         struct snd_pcm_runtime *runtime;
> -       struct snd_pcm *pcm = substream->pcm;
> +       struct snd_pcm *pcm;
>         struct snd_pcm_str *pstr = substream->pstr;
>  
>         snd_assert(substream != NULL, return -ENXIO);
> +       pcm = substream->pcm;
>         memset(info, 0, sizeof(*info));
>         info->card = pcm->card->number;
>         info->device = pcm->device;

can you also apply this other patch:

diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 9dd9bc7..b8f43f3 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -774,7 +774,7 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
        size_t size;
 
        snd_assert(rsubstream != NULL, return -EINVAL);
-       *rsubstream = NULL;
+//     *rsubstream = NULL; why NULL it ?? need to investigate more
        snd_assert(pcm != NULL, return -ENXIO);
        pstr = &pcm->streams[stream];
        if (pstr->substream == NULL || pstr->substream_count == 0)
@@ -795,8 +795,11 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
        case SNDRV_PCM_STREAM_PLAYBACK:
                if (pcm->info_flags & SNDRV_PCM_INFO_HALF_DUPLEX) {
                        for (substream = pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream; substream; substream = substream->
-                               if (SUBSTREAM_BUSY(substream))
+                               if (!substream)
                                        return -EAGAIN;
+
+                               if (SUBSTREAM_BUSY(substream))
+                                       continue;
                        }
                }
                break;
@@ -875,6 +878,10 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
        substream->ref_count = 1;
        substream->f_flags = file->f_flags;
        pstr->substream_opened++;
+
+       if (!substream)
+               printk(KERN_INFO "substream is NULL\n");
+
        *rsubstream = substream;
        return 0;
 }


-- 
balbi