Re: [PATCH 2/2] iio: at91-sama5d2: Limit requested watermark value to hwfifo size

[Paul Cercueil]

Hi Jonathan,

Le sam., juin 4 2022 at 16:05:57 +0100, Jonathan Cameron 
<jic23@xxxxxxxxxx> a écrit :
> On Sat, 22 Jan 2022 17:04:47 +0000
> Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
>
> >  On Mon, 17 Jan 2022 10:25:12 +0000
> >  Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:
> >
> >  > Instead of returning an error if the watermark value is too high, 
> > which
> >  > the core will silently ignore anyway, limit the value to the 
> > hardware
> >  > FIFO size; a lower-than-requested value is still better than 
> > using the
> >  > default, which is usually 1.
> >
> >  There is another potential error condition in this function which 
> > will
> >  also be ignored by the core.
> >
> >  As such whilst I agree this is a sensible thing to do in this
> >  particular case I think we should also be handling the error in the 
> > core.
> >
> >  I think it would be better to clean that up at the same time
> >  as these improvements - particularly as I'd guess you have a 
> > convenient
> >  test setup to check the error unwind is correct?
>
> Hi Paul,
>
> I was trawling through patchwork and realised this one is stalled.
>
> Thoughts on the above?

Totally forgot about this patch.

Aren't you afraid that if we start handling these errors in the core, 
we'll somehow break the ABI?

-Paul

> Thanks,
>
> Jonathan
>
> >  Thanks,
> >
> >  Jonathan
> >
> >  >
> >  > Cc: Eugen Hristev <eugen.hristev@xxxxxxxxxxxxx>
> >  > Cc: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
> >  > Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
> >  > Cc: Ludovic Desroches <ludovic.desroches@xxxxxxxxxxxxx>
> >  > Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  > ---
> >  >  drivers/iio/adc/at91-sama5d2_adc.c | 2 +-
> >  >  1 file changed, 1 insertion(+), 1 deletion(-)
> >  >
> >  > diff --git a/drivers/iio/adc/at91-sama5d2_adc.c 
> > b/drivers/iio/adc/at91-sama5d2_adc.c
> >  > index 854b1f81d807..5cc84f4a17bb 100644
> >  > --- a/drivers/iio/adc/at91-sama5d2_adc.c
> >  > +++ b/drivers/iio/adc/at91-sama5d2_adc.c
> >  > @@ -1752,7 +1752,7 @@ static int at91_adc_set_watermark(struct 
> > iio_dev *indio_dev, unsigned int val)
> >  >  	int ret;
> >  >
> >  >  	if (val > AT91_HWFIFO_MAX_SIZE)
> >  > -		return -EINVAL;
> >  > +		val = AT91_HWFIFO_MAX_SIZE;
> >  >
> >  >  	if (!st->selected_trig->hw_trig) {
> >  >  		dev_dbg(&indio_dev->dev, "we need hw trigger for DMA\n");