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

[Nuno Sá]

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@xxxxxxxxx>
> ---

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()

- 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;