Re: [PATCH RFC 1/6] iio: core: Match iio_device_claim_*() return semantics

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 04 Dec 2025 14:23:19 +0000
Nuno Sá <noname.nuno@gmail.com> wrote:

> On Wed, 2025-12-03 at 14:18 -0500, Kurt Borja wrote:
> > In order to improve API consistency with conditional locks, use
> > true/false return semantics in iio_device_claim_buffer_mode().
> > 
> > This also matches iio_device_claim_direct() return semantics.
> > 
> > Signed-off-by: Kurt Borja <kuurtb@gmail.com>
> > ---  
> 
> Even if the rest gets a NACK, I think at least this patch makes sense. In fact I
> would even extend it so that we have the same inline API with proper annotations:
> 
> https://elixir.bootlin.com/linux/v6.18/source/include/linux/iio/iio.h#L679
> 
> So it really has the same semantics as iio_device_claim_direct()

Yeah. This was on my mental todo list. So great to see Kurt
dealing with it! :)  These calls are much rarer than the direct ones
so I wasn't so fussed about getting the sparse coverage. Makes
sense to do it just wasn't high priority.

As Nuno, suggested though I would like the sparse support for these.

Jonathan

> 
> - Nuno Sá
> 
> >  drivers/iio/adc/ade9000.c                                 | 2 +-
> >  drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c | 5 +----
> >  drivers/iio/health/max30100.c                             | 2 +-
> >  drivers/iio/health/max30102.c                             | 2 +-
> >  drivers/iio/industrialio-core.c                           | 8 ++++----
> >  drivers/iio/light/opt4060.c                               | 2 +-
> >  include/linux/iio/iio.h                                   | 2 +-
> >  7 files changed, 10 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ade9000.c b/drivers/iio/adc/ade9000.c
> > index 2de8a718d62a..b345c4d1ef24 100644
> > --- a/drivers/iio/adc/ade9000.c
> > +++ b/drivers/iio/adc/ade9000.c
> > @@ -964,7 +964,7 @@ static irqreturn_t ade9000_dready_thread(int irq, void *data)
> >  	struct iio_dev *indio_dev = data;
> >  
> >  	/* Handle data ready interrupt from C4/EVENT/DREADY pin */
> > -	if (!iio_device_claim_buffer_mode(indio_dev)) {
> > +	if (iio_device_claim_buffer_mode(indio_dev)) {
> >  		ade9000_iio_push_buffer(indio_dev);
> >  		iio_device_release_buffer_mode(indio_dev);
> >  	}
> > diff --git a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> > b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> > index 9ac80e4b7d75..8ed4b2e410c8 100644
> > --- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> > +++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> > @@ -188,11 +188,8 @@ int cros_ec_sensors_push_data(struct iio_dev *indio_dev,
> >  	/*
> >  	 * Ignore samples if the buffer is not set: it is needed if the ODR is
> >  	 * set but the buffer is not enabled yet.
> > -	 *
> > -	 * Note: iio_device_claim_buffer_mode() returns -EBUSY if the buffer
> > -	 * is not enabled.
> >  	 */
> > -	if (iio_device_claim_buffer_mode(indio_dev) < 0)
> > +	if (!iio_device_claim_buffer_mode(indio_dev))
> >  		return 0;
> >  
> >  	out = (s16 *)st->samples;
> > diff --git a/drivers/iio/health/max30100.c b/drivers/iio/health/max30100.c
> > index 3d441013893c..3f3680c4b42f 100644
> > --- a/drivers/iio/health/max30100.c
> > +++ b/drivers/iio/health/max30100.c
> > @@ -417,7 +417,7 @@ static int max30100_read_raw(struct iio_dev *indio_dev,
> >  		 * Temperature reading can only be acquired while engine
> >  		 * is running
> >  		 */
> > -		if (iio_device_claim_buffer_mode(indio_dev)) {
> > +		if (!iio_device_claim_buffer_mode(indio_dev)) {
> >  			/*
> >  			 * Replacing -EBUSY or other error code
> >  			 * returned by iio_device_claim_buffer_mode()
> > diff --git a/drivers/iio/health/max30102.c b/drivers/iio/health/max30102.c
> > index a48c0881a4c7..288c2f37a4a2 100644
> > --- a/drivers/iio/health/max30102.c
> > +++ b/drivers/iio/health/max30102.c
> > @@ -476,7 +476,7 @@ static int max30102_read_raw(struct iio_dev *indio_dev,
> >  		 * shutdown; leave shutdown briefly when buffer not running
> >  		 */
> >  any_mode_retry:
> > -		if (iio_device_claim_buffer_mode(indio_dev)) {
> > +		if (!iio_device_claim_buffer_mode(indio_dev)) {
> >  			/*
> >  			 * This one is a *bit* hacky. If we cannot claim buffer
> >  			 * mode, then try direct mode so that we make sure
> > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> > index f69deefcfb6f..a10590ac4e17 100644
> > --- a/drivers/iio/industrialio-core.c
> > +++ b/drivers/iio/industrialio-core.c
> > @@ -2224,19 +2224,19 @@ EXPORT_SYMBOL_GPL(__iio_device_release_direct);
> >   *
> >   * Use with iio_device_release_buffer_mode().
> >   *
> > - * Returns: 0 on success, -EBUSY on failure.
> > + * Returns: true on success, false on failure.
> >   */
> > -int iio_device_claim_buffer_mode(struct iio_dev *indio_dev)
> > +bool iio_device_claim_buffer_mode(struct iio_dev *indio_dev)
> >  {
> >  	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> >  
> >  	mutex_lock(&iio_dev_opaque->mlock);
> >  
> >  	if (iio_buffer_enabled(indio_dev))
> > -		return 0;
> > +		return true;
> >  
> >  	mutex_unlock(&iio_dev_opaque->mlock);
> > -	return -EBUSY;
> > +	return false;
> >  }
> >  EXPORT_SYMBOL_GPL(iio_device_claim_buffer_mode);
> >  
> > diff --git a/drivers/iio/light/opt4060.c b/drivers/iio/light/opt4060.c
> > index 981c704e7df5..8cb3fa38077e 100644
> > --- a/drivers/iio/light/opt4060.c
> > +++ b/drivers/iio/light/opt4060.c
> > @@ -304,7 +304,7 @@ static int opt4060_set_driver_state(struct iio_dev *indio_dev,
> >  	struct opt4060_chip *chip = iio_priv(indio_dev);
> >  	int ret = 0;
> >  any_mode_retry:
> > -	if (iio_device_claim_buffer_mode(indio_dev)) {
> > +	if (!iio_device_claim_buffer_mode(indio_dev)) {
> >  		/*
> >  		 * This one is a *bit* hacky. If we cannot claim buffer mode,
> >  		 * then try direct mode so that we make sure things cannot
> > diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> > index 872ebdf0dd77..bf7b7337ff1b 100644
> > --- a/include/linux/iio/iio.h
> > +++ b/include/linux/iio/iio.h
> > @@ -687,7 +687,7 @@ static inline void iio_device_release_direct(struct iio_dev *indio_dev)
> >  	__release(indio_dev);
> >  }
> >  
> > -int iio_device_claim_buffer_mode(struct iio_dev *indio_dev);
> > +bool iio_device_claim_buffer_mode(struct iio_dev *indio_dev);
> >  void iio_device_release_buffer_mode(struct iio_dev *indio_dev);
> >  
> >  extern const struct bus_type iio_bus_type;