[alsa-devel] DMA buffer alignment

[Carlo Caione]

Hi,
I'm working with a SoC sound hw that requires that all the data
written into the DMA memory is aligned a 64 byte boundary. Actually
the alignment is required since the format of the data into the DMA
memory is (for a 2 channel 16bit audio): 16 samples for the left
channel followed by 16 samples for the right channel. If I try to
write anything that is not aligned to the 64 bytes I got audio
corruption (high pitched noise).
Several user-space programs (like aplay) work well with my hw, since
the buffer sent from the user-space is always (padded) of period-size
bytes, that is aligned to my 64 bytes boundary. Others (like
speaker-test) are not working because sometimes they snd_pcm_writei()
a buffer that is not multiple of 64 bytes. In general every time I
write into the DMA area a buffer that is not aligned, my hw pointer is
not aligned anymore with the 64 bytes and the noise starts.

IIUC it is not possible to force the user-space programs to send
buffers with a fixed size so the problem should be solved in
kernel-space (am I wrong on this point?).
Any suggestion on how to tackle this problem?

Thanks,

-- 
Carlo Caione