Re: [PATCH 5/8] iio: accel: kx022a: Switch to sparse friendly iio_device_claim/release_direct()

["Nuno Sá" <noname.nuno@gmail.com>]

On Wed, 2025-02-19 at 07:36 +0200, Matti Vaittinen wrote:
> On 18/02/2025 17:42, David Lechner wrote:
> > On 2/18/25 1:39 AM, Matti Vaittinen wrote:
> > > On 17/02/2025 16:01, Jonathan Cameron wrote:
> > > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > > 
> > > > These new functions allow sparse to find failures to release
> > > > direct mode reducing chances of bugs over the claim_direct_mode()
> > > > functions that are deprecated.
> > > > 
> > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > > Cc: Matti Vaittinen <mazziesaccount@gmail.com>
> > > > ---
> > > >    drivers/iio/accel/kionix-kx022a.c | 14 ++++++--------
> > > >    1 file changed, 6 insertions(+), 8 deletions(-)
> > > > 
> > > > diff --git a/drivers/iio/accel/kionix-kx022a.c
> > > > b/drivers/iio/accel/kionix-kx022a.c
> > > > index 727e007c5fc1..07dcf5f0599f 100644
> > > > --- a/drivers/iio/accel/kionix-kx022a.c
> > > > +++ b/drivers/iio/accel/kionix-kx022a.c
> > > > @@ -577,13 +577,12 @@ static int kx022a_write_raw(struct iio_dev *idev,
> > > >         * issues if users trust the watermark to be reached within known
> > > >         * time-limit).
> > > >         */
> > > > -    ret = iio_device_claim_direct_mode(idev);
> > > > -    if (ret)
> > > > -        return ret;
> > > > +    if (!iio_device_claim_direct(idev))
> > > > +        return -EBUSY;
> > > 
> > > Not really in the scope of this review - but in my opinion the logic of
> > > this check is terribly counter intuitive. I mean,
> > > 
> > > > +    if (iio_device_claim_direct(idev))
> > > > +        return -EBUSY;
> > 
> > I'm curious how you read this then. I read this as:
> > 
> > "If claiming direct mode succeeded, then return an error!"
> 
> I am used to seeing a pattern where function returning zero indicates a 
> success. I have no statistics but I believe this is true for a vast 
> majority of functions in the kernel. I believe this was the case with 
> the old 'iio_device_claim_direct_mode(idev)' too.
> 

Fair enough... Note though this is returning a boolean where true makes total
sense for the "good" case. I do agree it's not super clear just by reading the
code that the API is supposed to return a boolean.


- Nuno Sá