linux-kernel - [PATCH] ASoC: dpcm: Make BE prepare possible in suspend state

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Date:	Wed, 28 Oct 2015 10:15:34 +0800
From:	Koro Chen <koro.chen@...iatek.com>
To:	<broonie@...nel.org>, <tiwai@...e.de>
CC:	<srv_heupstream@...iatek.com>,
	<linux-mediatek@...ts.infradead.org>, <s.hauer@...gutronix.de>,
	<liam.r.girdwood@...ux.intel.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <alsa-devel@...a-project.org>,
	Koro Chen <koro.chen@...iatek.com>
Subject: [PATCH] ASoC: dpcm: Make BE prepare possible in suspend state

During suspend/resume, there is a flow that if a driver does not support
SNDRV_PCM_INFO_RESUME, it will fail at snd_pcm_resume(), and user space
can then issue SNDRV_PCM_IOCTL_PREPARE to let audio continue to play.

However, in dpcm_be_dai_prepare() it only allows BEs to be prepared
in state SND_SOC_DPCM_STATE_HW_PARAMS or SND_SOC_DPCM_STATE_STOP.
The BE state will then stay in SND_SOC_DPCM_STATE_SUSPEND, consequently
dpcm_be_dai_shutdown() is skipped in the end of playback and
be_substream->runtime is not cleared while this runtime is actually freed
by snd_pcm_detach_substream(). If another suspend comes, a NULL pointer
dereference will happen in snd_pcm_suspend() when accessing
BE substream's runtime.

Signed-off-by: Koro Chen <koro.chen@...iatek.com>
---
 sound/soc/soc-pcm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 3173958..5c41a58 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -2117,7 +2117,8 @@ int dpcm_be_dai_prepare(struct snd_soc_pcm_runtime *fe, int stream)
 			continue;

 		if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_PARAMS) &&
-		    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_STOP))
+		    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_STOP) &&
+		    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_SUSPEND))
 			continue;

 		dev_dbg(be->dev, "ASoC: prepare BE %s\n",
-- 
1.7.9.5

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