Re: [PATCH v3 1/7] iio: core: Add and export __iio_dev_mode_lock()

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 06 Jan 2026 03:06:56 -0500
Kurt Borja <kuurtb@gmail.com> wrote:

> Add unconditional wrappers around the internal IIO mode lock.
> 
> As mentioned in the documentation, this is not meant to be used by
> drivers, instead this will aid in the eventual addition of cleanup
> classes around conditional locks.
> 
> Signed-off-by: Kurt Borja <kuurtb@gmail.com>
Hi Kurt,

I'm being a bit conservative in looking to apply this so apologies
if it seems like I'm ignoring you! I wanted to give plenty of time
for others to take a look.

A few comments, but if we go with this version I'll tweak the
punctuation if I remember whilst applying.

Jonathan


> ---
>  drivers/iio/industrialio-core.c | 30 ++++++++++++++++++++++++++++++
>  include/linux/iio/iio.h         |  3 +++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index f69deefcfb6f..34867a860a84 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -2171,6 +2171,36 @@ int __devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev,
>  }
>  EXPORT_SYMBOL_GPL(__devm_iio_device_register);
>  
> +/**
> + * __iio_dev_mode_lock - Locks the current IIO device mode
> + * @indio_dev: the iio_dev associated with the device
> + *
> + * If the device is either in direct or buffer mode, it's guaranteed to stay
> + * that way until __iio_dev_mode_unlock() is called.
> + *
> + * This function is not meant to be used directly by drivers to protect internal
> + * state, a driver should have it's own mechanisms for that matter.

Nitpick, shouldn't be a comma.  Either

 * This function is not meant to be used directly by drivers to protect internal
 * state. A driver should have it's own mechanisms for that matter.

or if you like fancy uses of the semi colon.

 * This function is not meant to be used directly by drivers to protect internal
 * state; a driver should have it's own mechanisms for that matter.

> + *
> + * There are very few cases where a driver actually needs to lock the current
> + * mode unconditionally. It's recommended to use iio_device_claim_direct() or
> + * iio_device_claim_buffer_mode() pairs or related helpers instead.
> + */
> +void __iio_dev_mode_lock(struct iio_dev *indio_dev)
> +{
> +	mutex_lock(&to_iio_dev_opaque(indio_dev)->mlock);
> +}
> +EXPORT_SYMBOL_GPL(__iio_dev_mode_lock);
> +
> +/**
> + * __iio_dev_mode_unlock - Unlocks the current IIO device mode
> + * @indio_dev: the iio_dev associated with the device
> + */
> +void __iio_dev_mode_unlock(struct iio_dev *indio_dev)
> +{
> +	mutex_unlock(&to_iio_dev_opaque(indio_dev)->mlock);
> +}
> +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
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index 872ebdf0dd77..aecda887d833 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -661,6 +661,9 @@ void iio_device_unregister(struct iio_dev *indio_dev);
>  int __devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev,
>  			       struct module *this_mod);
>  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);
This is an interesting notation choice as there are several locks embedded
in iio_devs but I think it is the only one we want to expose so fair enough
if we don't see any false warnings from this!

Jonathan

>  bool __iio_device_claim_direct(struct iio_dev *indio_dev);
>  void __iio_device_release_direct(struct iio_dev *indio_dev);
>  
>