linux-kernel - Re: [PATCH v4 4/7] iio: core: Add cleanup.h support for iio_device_claim

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Message-ID: <fef660dc-8c81-420c-95b6-cc8649971894@baylibre.com>
Date: Sun, 18 Jan 2026 13:35:37 -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 v4 4/7] iio: core: Add cleanup.h support for
 iio_device_claim_*()

On 1/18/26 9:44 AM, Kurt Borja wrote:
> Add guard classes for iio_device_claim_*() conditional locks. This will
> aid drivers write safer and cleaner code when dealing with some common
> patterns.
> 
> These classes are not meant to be used directly by drivers (hence the
> __priv__ prefix). Instead, documented wrapper macros are provided to
> enforce the use of ACQUIRE() or guard() semantics and avoid the
> problematic scoped guard.
> 
> Suggested-by: Andy Shevchenko <andriy.shevchenko@...el.com>
> Reviewed-by: David Lechner <dlechner@...libre.com>
> Reviewed-by: Nuno Sá <nuno.sa@...log.com>
> Signed-off-by: Kurt Borja <kuurtb@...il.com>
> ---
>  include/linux/iio/iio.h | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index fa671e120e95..4a0a77fcfa8d 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -10,6 +10,7 @@
>  #include <linux/align.h>
>  #include <linux/device.h>
>  #include <linux/cdev.h>
> +#include <linux/cleanup.h>
>  #include <linux/compiler_types.h>
>  #include <linux/minmax.h>
>  #include <linux/slab.h>
> @@ -740,6 +741,70 @@ static inline bool iio_device_try_claim_buffer_mode(struct iio_dev *indio_dev)
>   */
>  #define iio_device_release_buffer_mode(indio_dev) __iio_dev_mode_unlock(indio_dev)
>  
> +/*
> + * These classes are not meant to be used directly by drivers (hence the
> + * __priv__ prefix). Instead, documented wrapper macros are provided below to
> + * enforce the use of ACQUIRE() or guard() semantics and avoid the problematic
> + * scoped guard variants.
> + */
> +DEFINE_GUARD(__priv__iio_dev_mode_lock, struct iio_dev *,
> +	     __iio_dev_mode_lock(_T), __iio_dev_mode_unlock(_T));
> +DEFINE_GUARD_COND(__priv__iio_dev_mode_lock, _try_direct,
> +		  iio_device_claim_direct(_T));
> +
> +/**
> + * IIO_DEV_ACQUIRE_DIRECT_MODE(dev, var) - Tries to acquire the direct mode
> + *					   lock with automatic release

Should be just IIO_DEV_ACQUIRE_DIRECT_MODE()

> + * @dev: IIO device instance
> + * @claim: Variable identifier to store acquire result
> + *
> + * Tries to acquire the direct mode lock with cleanup ACQUIRE() semantics and
> + * automatically releases it at the end of the scope. It most be always paired
> + * with IIO_DEV_ACQUIRE_ERR(), for example (notice the scope braces)::
> + *
> + *	switch() {
> + *	case IIO_CHAN_INFO_RAW: {
> + *		IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
> + *		if (IIO_DEV_ACQUIRE_FAILED(claim))
> + *			return -EBUSY;
> + *
> + *		...
> + *	}
> + *	case IIO_CHAN_INFO_SCALE:
> + *		...
> + *	...
> + *	}
> + *
> + * Context: Can sleep
> + */
> +#define IIO_DEV_ACQUIRE_DIRECT_MODE(dev, claim) \
> +	ACQUIRE(__priv__iio_dev_mode_lock_try_direct, claim)(dev)
> +
> +/**
> + * IIO_DEV_ACQUIRE_FAILED() - ACQUIRE_ERR() wrapper

This one is correct style.

> + * @claim: The claim variable passed to IIO_DEV_ACQUIRE_*_MODE()
> + *
> + * Return: true if failed to acquire the mode, otherwise false.
> + */
> +#define IIO_DEV_ACQUIRE_FAILED(claim) \
> +	ACQUIRE_ERR(__priv__iio_dev_mode_lock_try_direct, &(claim))
> +
> +/**
> + * IIO_DEV_GUARD_CURRENT_MODE - Acquires the mode lock with automatic release

Missing ()

> + * @dev: IIO device instance
> + *
> + * Acquires the mode lock with cleanup guard() semantics. It is usually paired
> + * with iio_buffer_enabled().
> + *
> + * This should *not* be used to protect internal driver state and it's use in
> + * general is *strongly* discouraged. Use any of the IIO_DEV_ACQUIRE_*_MODE()
> + * variants.
> + *
> + * Context: Can sleep
> + */
> +#define IIO_DEV_GUARD_CURRENT_MODE(dev) \
> +	guard(__priv__iio_dev_mode_lock)(dev)
> +
>  extern const struct bus_type iio_bus_type;
>  
>  /**
>