Re: [PATCH 1/5] ASoC: sh: rz-ssi: Drop calling rz_ssi_pio_recv() recursively

[Cezary Rojewski]

On 2022-01-10 7:44 PM, Pavel Machek wrote:
> Hi!
>
> > > On 2022-01-10 10:47 AM, Lad Prabhakar wrote:
> > > > Instead of recursively calling rz_ssi_pio_recv() use a while loop
> > > > to read the samples from RX fifo.
> > >
> > > Recursion and loops are means for doing something repeatedly. Could you
> > > specify _why_ such change was made i.e. the conversion from one method
> > > into the other? I bet the code is not being changed for the sake of
> > > changing it, the reason is simply missing in the commit message.
> > I had feedback from Pavel "recursion is unwelcome in kernel due to
> > limited stack use." which I did agree with as a result I have come up
> > with this patch. Also to add this driver will later be used on Renesas
> > RZ/A2 SoC's which runs with limited memory.

...

> Yes, loop is better.
>
> I'd actually do while(true) and avoid using the done variable.
>
>      if (!(!frames_left && fifo_samples >= runtime->channels))
>                break;
>
> will do the trick. Better yet, do
>
>      if (frames_left || fifo_samples < runtime->channels)
>                break;
>
> because double negation is quite confusing and looks like typo.

You could achieve similar results by enlisting do-while loop. That's my 
proposal.


Regards,
Czarek