Re: [PATCH v5 2/7] iio: core: Refactor iio_device_claim_direct() implementation

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 20 Jan 2026 01:20:42 -0500
Kurt Borja <kuurtb@gmail.com> wrote:

> In order to eventually unify the locking API, implement
> iio_device_claim_direct() fully inline, with the use of
> __iio_dev_mode_lock(), which takes care of sparse annotations.
> 
> Reviewed-by: David Lechner <dlechner@baylibre.com>
> Reviewed-by: Nuno Sá <nuno.sa@analog.com>
> Signed-off-by: Kurt Borja <kuurtb@gmail.com>

So sparse does change what it moans about with this one in precisely one instance
There are 9 false positives with Al Viro's updated sparse - I haven't checked the
original one recently.

Anyhow, 
drivers/iio/adc/ad7173.c:416:12: warning: context imbalance in 'ad7173_set_filter_type' - different lock contexts for basic block
becomes

drivers/iio/adc/ad7173.c:425:9: warning: context imbalance in 'ad7173_set_filter_type' - unexpected unlock                                                          

Lets go with a bit meh for that and move on...

> ---
>  drivers/iio/industrialio-core.c | 44 -----------------------------------------
>  include/linux/iio/iio.h         | 40 ++++++++++++++++++++++++++-----------
>  2 files changed, 28 insertions(+), 56 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index db803267df6e..0f8e3aa98b72 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -2201,50 +2201,6 @@ void __iio_dev_mode_unlock(struct iio_dev *indio_dev)
>  }
>  EXPORT_SYMBOL_GPL(__iio_dev_mode_unlock);
>  
> -/**
> - * __iio_device_claim_direct - Keep device in direct mode
> - * @indio_dev:	the iio_dev associated with the device
> - *
> - * If the device is in direct mode it is guaranteed to stay
> - * that way until __iio_device_release_direct() is called.
> - *
> - * Use with __iio_device_release_direct().
> - *
> - * Drivers should only call iio_device_claim_direct().
> - *
> - * Returns: true on success, false on failure.
> - */
> -bool __iio_device_claim_direct(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)) {
> -		mutex_unlock(&iio_dev_opaque->mlock);
> -		return false;
> -	}
> -	return true;
> -}
> -EXPORT_SYMBOL_GPL(__iio_device_claim_direct);
> -
> -/**
> - * __iio_device_release_direct - releases claim on direct mode
> - * @indio_dev:	the iio_dev associated with the device
> - *
> - * Release the claim. Device is no longer guaranteed to stay
> - * in direct mode.
> - *
> - * Drivers should only call iio_device_release_direct().
> - *
> - * Use with __iio_device_claim_direct()
> - */
> -void __iio_device_release_direct(struct iio_dev *indio_dev)
> -{
> -	mutex_unlock(&to_iio_dev_opaque(indio_dev)->mlock);
> -}
> -EXPORT_SYMBOL_GPL(__iio_device_release_direct);
> -
>  /**
>   * iio_device_claim_buffer_mode - Keep device in buffer mode
>   * @indio_dev:	the iio_dev associated with the device
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index aecda887d833..e263ab5eeccf 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -664,31 +664,47 @@ int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp);
>  
>  void __iio_dev_mode_lock(struct iio_dev *indio_dev) __acquires(indio_dev);
>  void __iio_dev_mode_unlock(struct iio_dev *indio_dev) __releases(indio_dev);
> -bool __iio_device_claim_direct(struct iio_dev *indio_dev);
> -void __iio_device_release_direct(struct iio_dev *indio_dev);
>  
>  /*
>   * Helper functions that allow claim and release of direct mode
>   * in a fashion that doesn't generate many false positives from sparse.
>   * Note this must remain static inline in the header so that sparse
> - * can see the __acquire() marking. Revisit when sparse supports
> - * __cond_acquires()
> + * can see the __acquires() and __releases() annotations.
> + */
> +
> +/**
> + * iio_device_claim_direct() - Keep device in direct mode
> + * @indio_dev:	the iio_dev associated with the device
> + *
> + * If the device is in direct mode it is guaranteed to stay
> + * that way until iio_device_release_direct() is called.
> + *
> + * Use with iio_device_release_direct().
> + *
> + * Returns: true on success, false on failure.
>   */
>  static inline bool iio_device_claim_direct(struct iio_dev *indio_dev)
>  {
> -	if (!__iio_device_claim_direct(indio_dev))
> -		return false;
> +	__iio_dev_mode_lock(indio_dev);
>  
> -	__acquire(iio_dev);
> +	if (iio_buffer_enabled(indio_dev)) {
> +		__iio_dev_mode_unlock(indio_dev);
> +		return false;
> +	}
>  
>  	return true;
>  }
>  
> -static inline void iio_device_release_direct(struct iio_dev *indio_dev)
> -{
> -	__iio_device_release_direct(indio_dev);
> -	__release(indio_dev);
> -}
> +/**
> + * iio_device_release_direct() - Releases claim on direct mode
> + * @indio_dev:	the iio_dev associated with the device
> + *
> + * Release the claim. Device is no longer guaranteed to stay
> + * in direct mode.
> + *
> + * Use with iio_device_claim_direct().
> + */
> +#define iio_device_release_direct(indio_dev) __iio_dev_mode_unlock(indio_dev)
>  
>  int iio_device_claim_buffer_mode(struct iio_dev *indio_dev);
>  void iio_device_release_buffer_mode(struct iio_dev *indio_dev);
>