[alsa-devel] [PATCH v3 3/5] ASoC: generic-dmaengine-pcm: Prepare formats mask for valid physical sample sizes

[Peter Ujfalusi]

Based on the dma_slave_caps's addr_widths queried from the dma driver
prepare the hw.formats mask to include only formats which is supported by
the DMA engine.
In case the dma driver does not implement the slave_caps the default
assumption is that it supports 1, 2 and 4 bytes widths.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
---

I know that the format validation could be done like this:

+		if (bits > 0 && bits <=64 && !(bits % 8) &&
+		    (addr_widths & (1 << (bits / 8))))
+				hw.formats |= (1LL << i);

But I think the switch() implementation is more readable.


 sound/soc/soc-generic-dmaengine-pcm.c | 37 ++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
index 5bace124ef43..6307f85e871b 100644
--- a/sound/soc/soc-generic-dmaengine-pcm.c
+++ b/sound/soc/soc-generic-dmaengine-pcm.c
@@ -119,7 +119,10 @@ static int dmaengine_pcm_set_runtime_hwparams(struct snd_pcm_substream *substrea
 	struct snd_dmaengine_dai_dma_data *dma_data;
 	struct dma_slave_caps dma_caps;
 	struct snd_pcm_hardware hw;
-	int ret;
+	u32 addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
+			  BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
+			  BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
+	int i, ret;
 
 	if (pcm->config && pcm->config->pcm_hardware)
 		return snd_soc_set_runtime_hwparams(substream,
@@ -146,6 +149,38 @@ static int dmaengine_pcm_set_runtime_hwparams(struct snd_pcm_substream *substrea
 			hw.info |= SNDRV_PCM_INFO_PAUSE | SNDRV_PCM_INFO_RESUME;
 		if (dma_caps.residue_granularity <= DMA_RESIDUE_GRANULARITY_SEGMENT)
 			hw.info |= SNDRV_PCM_INFO_BATCH;
+
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			addr_widths = dma_caps.dstn_addr_widths;
+		else
+			addr_widths = dma_caps.src_addr_widths;
+	}
+
+	/*
+	 * Prepare formats mask for valid/allowed sample types. If the dma does
+	 * not have support for the given physical word size, it needs to be
+	 * masked out so user space can not use the format which produces
+	 * corrupted audio.
+	 * In case the dma driver does not implement the slave_caps the default
+	 * assumption is that it supports 1, 2 and 4 bytes widths.
+	 */
+	for (i = 0; i <= SNDRV_PCM_FORMAT_LAST; i++) {
+		int bits = snd_pcm_format_physical_width(i);
+
+		/* Enable only samples with DMA supported physical widths */
+		switch (bits) {
+		case 8:
+		case 16:
+		case 24:
+		case 32:
+		case 64:
+			if (addr_widths & (1 << (bits / 8)))
+				hw.formats |= (1LL << i);
+			break;
+		default:
+			/* Unsupported types */
+			break;
+		}
 	}
 
 	return snd_soc_set_runtime_hwparams(substream, &hw);
-- 
2.0.0