[alsa-devel] [PATCH 2/4] soc-dai: add bitfields for hardware I2S formats

[pHilipp Zabel]

On Thu, Mar 5, 2009 at 1:55 PM, Daniel Mack <daniel at caiaq.de> wrote:
> On Thu, Mar 05, 2009 at 12:03:35PM +0000, Mark Brown wrote:
>> > > The other option would be to use the TDM mode interface to set this up
>> > > since that's roughly what it is; my main concern here is that we already
>> > > have two ways of doing this and I'd like to try to keep the number down
>> > > for consistency.
>>
>> > Probably a matter of taste, but IMO TDM mode is not the place either.
>> > Userspace could decide sending out 24bit samples out of a sudden (which
>> > the CPU DAI might accept) and in this case, you'd need some special
>> > logic in the board file again to set up deviders, time slots etc, right?
>>
>> That's why the clocking interface is generally used here - it's more
>> orthogonal.
>
> Hmm, how would you express 24 sample bits with 32 clocks per channel? I
> might not have gotten your point yet - could you provide an example?

I'm still a bit confused by the alsa formats and how they interact
with the SSP formats.

Do I understand correctly that S24_3LE (24-bit packed in 3 bytes)
can't be supported due to limitations in (at least PXA27x's) DMA
engine?
So the remaining 24-bit formats are S24_LE and S32_LE anyway, both of
which are 24-bit packed in 32 bits (either LSB or MSB aligned).

regards
Philipp