linux-kernel - Re: [PATCH v3 3/3] staging: iio: ad9832: Add minor improvements to ad9832_write

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Message-ID: <CAKUZ0zLgH9Ec5FMEjXa59-bBEVooEQUOeGuZ9OJw=A3P3OWp5A@mail.gmail.com>
Date: Thu, 24 Apr 2025 18:29:57 -0400
From: Gabriel Shahrouzi <gshahrouzi@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: gregkh@...uxfoundation.org, lars@...afoo.de, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-staging@...ts.linux.dev, 
	Michael.Hennerich@...log.com, skhan@...uxfoundation.org, 
	linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH v3 3/3] staging: iio: ad9832: Add minor improvements to ad9832_write_powerdown

On Mon, Apr 21, 2025 at 7:40 AM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Sun, 20 Apr 2025 13:54:19 -0400
> Gabriel Shahrouzi <gshahrouzi@...il.com> wrote:
>
> > Minimize size of type that needs to be used by replacing unsigned long
> > with bool. Avoid redundancy by checking if cached power state is the
> > same as the one requested.
> >
> > Signed-off-by: Gabriel Shahrouzi <gshahrouzi@...il.com>
> > ---
> >  drivers/staging/iio/frequency/ad9832.c | 18 ++++++++++++------
> >  1 file changed, 12 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
> > index a8fc20379efed..2ab6026d56b5c 100644
> > --- a/drivers/staging/iio/frequency/ad9832.c
> > +++ b/drivers/staging/iio/frequency/ad9832.c
> > @@ -173,13 +173,19 @@ static ssize_t ad9832_write_powerdown(struct device *dev, struct device_attribut
> >       struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> >       struct ad9832_state *st = iio_priv(indio_dev);
> >       int ret;
> > -     unsigned long val;
> > +     bool val;
> > +     bool cur;
> >
> > -     ret = kstrtoul(buf, 10, &val);
> > +     ret = kstrtobool(buf, &val);
> That could have been done in the previous patch as you are changing the ABI anyway.
Got it.
> >       if (ret)
> > -             goto error_ret;
> > +             return ret;
> >
> >       mutex_lock(&st->lock);
> > +
> > +     cur = !!(st->ctrl_src & AD9832_SLEEP);
>
> Worth thinking about whether this driver will ever be converted to regmap with regcache.
> If that's a reasonable thing to do long term this sort of optimization adds nothing
> useful as we'll skip the right anwyay if the driver is already in the appropriate state.
Got it.
>
> This isn't a high performance path, so I'd not bother with the check for now.
Got it.
>
> > +     if (val == cur)
> > +             goto unlock;
> > +
> >       if (val)
> >               st->ctrl_src |= AD9832_SLEEP;
> >       else
> > @@ -189,10 +195,10 @@ static ssize_t ad9832_write_powerdown(struct device *dev, struct device_attribut
> >       st->data = cpu_to_be16((AD9832_CMD_SLEEPRESCLR << CMD_SHIFT) |
> >                               st->ctrl_src);
> >       ret = spi_sync(st->spi, &st->msg);
> If this fails, where doe ret end up? Looks to me like we now don't report the error
> Anyhow, see guard() comment in previous patch.  These days we can avoid a lot of
> this complexity by using that to allow direct returns where we first see the error.
Ah right, fixed that for the new version and removed the complexity by
directly returning.
>
> > -     mutex_unlock(&st->lock);
> >
> > -error_ret:
> > -     return ret ? ret : len;
> > +unlock:
> > +     mutex_unlock(&st->lock);
> > +     return len;
> >  }
> >
> >  static ssize_t ad9832_write(struct device *dev, struct device_attribute *attr,
>