[alsa-devel] ASoC and a codec that can't be controlled
timur at freescale.com
Thu May 31 20:55:27 CEST 2007
Liam Girdwood wrote:
>> On big-endian platforms like mine, CS4270_FORMATS will be SNDRV_PCM_FORMAT_S24_BE and on
>> little-endian platforms it will be SNDRV_PCM_FORMAT_S24_LE. Assuming the I2S registers
>> are the same endian as the platform, will this work?
> I think this probably depends on how your audio FIFO's align the data
> received from memory/DMA. They should do any bit reordering based on
> the audio format, and size etc set in the control register. (Although,
Ok, I'm a little confused. I was going to specify the SNDRV_PCM_FORMAT_S24_BE for my I2C
device because the actual 32-bit memory-mapped registers are big-endian. The structure
definition even uses __be32 for each field.
My goal was to specify a single value (i.e. SNDRV_PCM_FORMAT_S24_BE) such that ALSA would
give me a 32-bit quantity that exactly matches what my device expects.
I wish asound.h had more documentation. I don't know what any of these macros *really* mean.
>> #define CS4270_FORMATS (SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S24_BE)
>> That would tell ALSA that the CS4270 supports both formats, which isn't technically true,
>> but it wouldn't matter because the I2S interface is what determines the actual
>> "endianness" of the serial data.
> This looks fine as a workaround atm, I'll try and have a look at this
> bug tomorrow so we don't need to do this.
Ok, I'll do this for now.
Linux Kernel Developer @ Freescale
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