Re: [PATCH 4/4] ALSA: pcm_dmaengine: Correct support for 3 physical bytes samples

Peter Ujfalusi
2014-07-02T12:56:33Z

On 07/02/2014 03:48 PM, Lars-Peter Clausen wrote:
>> per discussion over the irc with Lars we could extend the masking to other
>> widths as well, which would look something like this:
>> u32 addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
>> BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
>> BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
>> ...
>> /*
>> * 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.
>> */
>> if (!dma_get_slave_caps(prtd->dma_chan, &dma_caps)) {
>> if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
>> addr_widths = dma_caps.dstn_addr_widths;
>> else
>> addr_widths = dma_caps.src_addr_widths;
>> }
>>
>> for (i = 0; i <= SNDRV_PCM_FORMAT_LAST; i++) {
>> int bits = snd_pcm_format_physical_width(i);
>>
>> switch (bits) {
>> case 8:
>> if (!(addr_widths & BIT(DMA_SLAVE_BUSWIDTH_1_BYTE)))
>> fmt_mask |= (1LL << i);
>> break;
>> case 16:
>> if (!(addr_widths & BIT(DMA_SLAVE_BUSWIDTH_2_BYTES)))
>> fmt_mask |= (1LL << i);
>> break;
>> case 24:
>> if (!(addr_widths & BIT(DMA_SLAVE_BUSWIDTH_3_BYTES)))
>> fmt_mask |= (1LL << i);
>> break;
>> case 32:
>> if (!(addr_widths & BIT(DMA_SLAVE_BUSWIDTH_4_BYTES)))
>> fmt_mask |= (1LL << i);
>> break;
>> case 64:
>> if (!(addr_widths & BIT(DMA_SLAVE_BUSWIDTH_8_BYTES)))
>> fmt_mask |= (1LL << i);
>> break;
>> default:
>> fmt_mask |= (1LL << i);
>> break;
>> }
>> }
>>
>> Is this sounds better?
>
> Sounds good. I think we can assume that DMA_SLAVE_BUSWIDTH_1_BYTE = 1, ...
> So (addr_width & BIT(bits / 8)) should work fine and we do not need to
> duplicate the case branches.
>
> The other thing is this should go into dmaengine_pcm_set_runtime_hwparams()
> where we also restrict the other hardware parameters based on the dmaengine
> capabilities.

true

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