linux-kernel - Re: [PATCH v2 3/5] ASoC: generic-dmaengine-pcm: Prepare formats mask for valid physical sample sizes

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Date:	Wed, 02 Jul 2014 15:47:55 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Peter Ujfalusi <peter.ujfalusi@...com>
Cc:	<vinod.koul@...el.com>, <dan.j.williams@...el.com>,
	<lars@...afoo.de>, Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>, <joelf@...com>,
	<nsekhar@...com>, <linux-kernel@...r.kernel.org>,
	<alsa-devel@...a-project.org>, <dmaengine@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] ASoC: generic-dmaengine-pcm: Prepare formats mask for valid physical sample sizes

At Wed, 2 Jul 2014 16:29:21 +0300,
Peter Ujfalusi wrote:
> 
> 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@...com>
> ---
>  sound/soc/soc-generic-dmaengine-pcm.c | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
> index 5bace124ef43..c295e1754d1a 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 +149,27 @@ 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);

Better to add a negative value check.  Some formats return -EINVAL.

> +
> +		/* Enable only samples with DMA supported physical widths */
> +		if (addr_widths & BIT(bits / 8))

Just nitpicking: Using BIT() for 32bit int isn't always a wise choice
since BIT() is defined as unsigned long.  This is a generic problem,
though, as we see many codes using BIT() wrongly (and thus get
compiler warnings on 64bit machines).  We should introduce a new macro 
for 32bit int...


Takashi
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