linux-kernel - Re: [PATCH v3 4/7] iio: core: Add cleanup.h support for iio_device_claim

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Message-ID: <20260116202928.6ec155ed@jic23-huawei>
Date: Fri, 16 Jan 2026 20:29:28 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Kurt Borja <kuurtb@...il.com>
Cc: Andy Shevchenko <andriy.shevchenko@...el.com>, Lars-Peter Clausen
 <lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>, 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>,
 David Lechner <dlechner@...libre.com>, 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 v3 4/7] iio: core: Add cleanup.h support for
 iio_device_claim_*()

On Tue, 06 Jan 2026 03:06:59 -0500
Kurt Borja <kuurtb@...il.com> 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>
> Signed-off-by: Kurt Borja <kuurtb@...il.com>
Very nice. Trivial comments inline.

J
> ---
>  include/linux/iio/iio.h | 71 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 71 insertions(+)
> 
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index d8af0456f966..c795f731f2d8 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 +741,76 @@ 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 bellow to

below

> + * 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
> + * @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::
> + *
> + *	IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
> + *	if (IIO_DEV_ACQUIRE_FAILED(&claim))
> + *		return -EBUSY;

I don't think we need two examples. I'd just go with the second one as
the braces is indeed something people get wrong with the other cleanup.h stuff.

> + *
> + * ...or a more common scenario (notice scope the 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
> + * @claim_ptr: Pointer to the claim variable passed to IIO_DEV_ACQUIRE_*_MODE()
> + *
> + * Return: true if acquired the mode failed, otherwise false.
> + */
> +#define IIO_DEV_ACQUIRE_FAILED(claim_ptr) \
> +	ACQUIRE_ERR(__priv__iio_dev_mode_lock_try_direct, claim_ptr)
> +
> +/**
> + * IIO_DEV_GUARD_CURRENT_MODE - Acquires the mode lock with automatic release
> + * @_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;
>  
>  /**
>