On 12/16/21 7:53 AM, Kuninori Morimoto wrote:
Hi ALSA ML
At soc_pcm_apply_msb(),
(A) part finds max sig_bits for Codec, and
(B) part finds max sig_bits for CPU
and, set it to substream via soc_pcm_set_msb() at (X), (Y).
static void soc_pcm_apply_msb()
{
...
^ for_each_rtd_codec_dais(rtd, i, codec_dai) {
(A) ...
v bits = max(pcm_codec->sig_bits, bits);
}
^ for_each_rtd_cpu_dais(rtd, i, cpu_dai) {
(B) ...
v cpu_bits = max(pcm_cpu->sig_bits, cpu_bits);
}
(X) soc_pcm_set_msb(substream, bits);
(Y) soc_pcm_set_msb(substream, cpu_bits);
}
I wonder do we need both (X) (Y) ?
I think we can merge (A) and (B) (= find Codec/CPU max sig_bits),
and call soc_pcm_set_msb() once, but am I misunderstand ?
We need both. Or alternatively you could write
soc_pcm_set_msb(substream, min(bits, cpu_bits)).
What this does is it computes the maximum msb bits from both the CPU
side and the CODEC side and then sets the msb bits reported to userspace
to the minimum of the two.
The largest number of MSBs we'll see on the CODEC side is the max() and
the largest number of MSBs we'll see on the CPU side is the max(). And
the number of MSBs that the application will be able to see is the
smaller of the two.
