linux-kernel - [PATCH] ASoC: pcm: allow changing the playback/capture rates for symmetric links

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Date:	Wed, 27 Apr 2016 10:49:19 +0200
From:	Peter Rosin <peda@...ntia.se>
To:	<alsa-devel@...a-project.org>
CC:	Peter Rosin <peda@...ntia.se>, Liam Girdwood <lgirdwood@...il.com>,
	"Mark Brown" <broonie@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] ASoC: pcm: allow changing the playback/capture rates for symmetric links

The below program fails on a dai link with symmetric rates without this
patch. The patch makes it work.

#include <sys/soundcard.h>
#include <unistd.h>
#include <fcntl.h>
#include <stropts.h>
#include <stdio.h>

int
main(void)
{
    int fd;
    int format;
    int channels;
    int speed;

    if ((fd = open("/dev/dsp", O_WRONLY, 0)) == -1) {
            perror("open");
            return 1;
    }
    format = AFMT_S16_LE;
    if (ioctl(fd, SNDCTL_DSP_SETFMT, &format) == -1) {
            perror("SNDCTL_DSP_SETFMT");
            return 1;
    }
    channels = 2;
    if (ioctl(fd, SNDCTL_DSP_CHANNELS, &channels) == -1) {
            perror("SNDCTL_DSP_CHANNELS");
            return 1;
    }
    speed = 22050;
    if (ioctl(fd, SNDCTL_DSP_SPEED, &speed) == -1) {
            perror("SNDCTL_DSP_SPEED");
            return 1;
    }
    return 0;
}

Signed-off-by: Peter Rosin <peda@...ntia.se>
---
 sound/soc/soc-pcm.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 35fe58f4fa86..1e876ff23524 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -237,6 +237,14 @@ static int soc_pcm_params_symmetry(struct snd_pcm_substream *substream,
 	struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
 	unsigned int rate, channels, sample_bits, symmetry, i;
 
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		if (!cpu_dai->capture_active)
+			return 0;
+	} else if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) {
+		if (!cpu_dai->playback_active)
+			return 0;
+	}
+
 	rate = params_rate(params);
 	channels = params_channels(params);
 	sample_bits = snd_pcm_format_physical_width(params_format(params));
-- 
2.1.4