Re: [PATCH v3 2/3] iio: accel: Support Kionix/ROHM KX022A accelerometer

[Matti Vaittinen]

On 10/21/22 13:49, Andy Shevchenko wrote:
> On Fri, Oct 21, 2022 at 10:10:08AM +0300, Matti Vaittinen wrote:
> > On 10/20/22 17:34, Andy Shevchenko wrote:
> > > On Thu, Oct 20, 2022 at 02:37:15PM +0300, Matti Vaittinen wrote:
>
> ...
>
> > > > +	ret = regmap_bulk_read(data->regmap, chan->address, &data->buffer,
> > > > +			       sizeof(__le16));
> > > > +	if (ret)
> > > > +		return ret;
> > > > +
> > > > +	*val = le16_to_cpu(data->buffer[0]);
> > >
> > > 'p'-variant of the above would look better
> > >
> > > 	*val = le16_to_cpup(data->buffer);
> > >
> > > since it will be the same as above address without any additional arithmetics.
> >
> > I guess there is no significant performance difference? To my eye the
> > le16_to_cpu(data->buffer[0]) is much more clear. I see right from the call
> > that we have an array here and use the first member. If there is no obvious
> > technical merit for using le16_to_cpup(data->buffer) over
> > le16_to_cpu(data->buffer[0]), then I do really prefer the latter for
> > clarity.
>
> Then you probably wanted to have &data->buffer[0] as a parameter to
> regmap_bulk_read()?

Yes! Thanks.

> ...
>
> > > > +	if (data->trigger_enabled) {
> > > > +		iio_trigger_poll_chained(data->trig);
> > > > +		ret = IRQ_HANDLED;
> > > > +	}
> > > > +
> > > > +	if (data->state & KX022A_STATE_FIFO) {
> > >
> > > > +		ret = __kx022a_fifo_flush(idev, KX022A_FIFO_LENGTH, true);
> > > > +		if (ret > 0)
> > > > +			ret = IRQ_HANDLED;
> > >
> > > I don't like it. Perhaps
> > >
> > > 	bool handled = false;
> > > 	int ret;
> > >
> > > 	...
> > > 		ret = ...
> > > 		if (ret > 0)
> > > 			handled = true;
> > > 	...
> > >
> > > 	return IRQ_RETVAL(handled);
> >
> > I don't see the benefit of adding another variable 'handled'.
> > If I understand correctly, it just introduces one extra 'if' in IRQ thread
> > handling while hiding the return value in IRQ_RETVAL() - macro.
> >
> > I do like seeing the IRQ_NONE being returned by default and IRQ_HANDLED only
> > when "handlers" are successfully executed. Adding extra variable just
> > obfuscates this (from my eyes) while adding also the additional 'if'.
>
> You assigning semantically different values to the same variable inside the
> function.

Ah, yes! This was really a bug making it way in. I guess you may just 
have saved me from some not-that-funny debugging session... Well spotted!

I still don't like hiding the IRQ_HANDLED / IRQ_NONE. I'll just go for

        if (data->state & KX022A_STATE_FIFO) { 

                int ok; 



                ok = __kx022a_fifo_flush(idev, KX022A_FIFO_LENGTH, 
true);
                if (ok > 0) 

                        ret = IRQ_HANDLED; 

        }

for v4. (Which I try to send still today before my memory is flushed by 
the weekend :])

Thanks a lot!

Yours
	-- Matti

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~