linux-kernel - Re: [PATCH v2 1/7] iio: core: Add and export __iio_dev_mode

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Message-ID: <92d07935-b2b5-4cf3-bd45-654d77cdc23b@baylibre.com>
Date: Tue, 23 Dec 2025 11:19:38 -0600
From: David Lechner <dlechner@...libre.com>
To: Kurt Borja <kuurtb@...il.com>,
 Andy Shevchenko <andriy.shevchenko@...el.com>,
 Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Benson Leung <bleung@...omium.org>,
 Antoniu Miclaus <antoniu.miclaus@...log.com>,
 Gwendal Grignou <gwendal@...omium.org>,
 Shrikant Raskar <raskar.shree97@...il.com>,
 Per-Daniel Olsson <perdaniel.olsson@...s.com>
Cc: Nuno Sá <nuno.sa@...log.com>,
 Andy Shevchenko <andy@...nel.org>, Guenter Roeck <groeck@...omium.org>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev
Subject: Re: [PATCH v2 1/7] iio: core: Add and export __iio_dev_mode_lock()

On 12/11/25 8:45 PM, Kurt Borja wrote:
> Add infallible wrappers around the internal IIO mode lock.

Not sure what "infallible" is supposed to mean in this context. Maybe
referring to autocleanup?

> 
> 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@...il.com>
> ---
>  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..1cce2d1ecef1 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.
> + *
> + * There are very few cases where a driver actually needs to lock any mode. It's
> + * *strongly* recommended to use iio_device_claim_direct() or

I wouldn't even say "strongly recommend". Just say "use these instead".

In the exceptions, likely the autocleanup version should be used as is
the case currently.

> + * iio_device_claim_buffer_mode() pairs or related helpers.
> + */
> +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);
>  bool __iio_device_claim_direct(struct iio_dev *indio_dev);
>  void __iio_device_release_direct(struct iio_dev *indio_dev);
>  
>