linux-kernel - Re: [PATCH RFC 6/6] iio: core: mark scan_timestamp as _

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Message-ID: <20241130141954.07423793@jic23-huawei>
Date: Sat, 30 Nov 2024 14:19:54 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Vasileios Amoiridis <vassilisamir@...il.com>
Cc: lars@...afoo.de, krzysztof.kozlowski@...aro.org, nuno.sa@...log.com,
 u.kleine-koenig@...libre.com, abhashkumarjha123@...il.com,
 jstephan@...libre.com, dlechner@...libre.com, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 6/6] iio: core: mark scan_timestamp as __private

On Sat, 30 Nov 2024 01:27:10 +0100
Vasileios Amoiridis <vassilisamir@...il.com> wrote:

> Since there are no more direct accesses to the indio_dev->scan_timestamp
> value, it can be marked as __private and use the macro ACCESS_PRIVATE()
> in order to access it. Like this, static checkers will be able to inform
> in case someone tries to either write to the value, or read its value
> directly.
> 
> Signed-off-by: Vasileios Amoiridis <vassilisamir@...il.com>
> ---
>  drivers/iio/industrialio-buffer.c | 2 +-
>  include/linux/iio/iio.h           | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 8104696cd475..c332741f3cf4 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -1137,7 +1137,7 @@ static int iio_enable_buffers(struct iio_dev *indio_dev,
>  	int ret;
>  
>  	indio_dev->active_scan_mask = config->scan_mask;
> -	indio_dev->scan_timestamp = config->scan_timestamp;
> +	ACCESS_PRIVATE(indio_dev, scan_timestamp) = config->scan_timestamp;
>  	indio_dev->scan_bytes = config->scan_bytes;
>  	iio_dev_opaque->currentmode = config->mode;
>  
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index 5661794d1127..669b4ef1280d 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -611,7 +611,7 @@ struct iio_dev {
>  	const unsigned long		*available_scan_masks;
>  	unsigned int			__private masklength;
>  	const unsigned long		*active_scan_mask;
> -	bool				scan_timestamp;
> +	bool				__private scan_timestamp;
>  	struct iio_trigger		*trig;
>  	struct iio_poll_func		*pollfunc;
>  	struct iio_poll_func		*pollfunc_event;
> @@ -908,7 +908,7 @@ int iio_active_scan_mask_index(struct iio_dev *indio_dev);
>   */
>  static inline bool iio_is_soft_ts_enabled(const struct iio_dev *indio_dev)
>  {
> -	return indio_dev->scan_timestamp;
> +	return ACCESS_PRIVATE(indio_dev, scan_timestamp);
If we only end up with one use of this (based on feedback on other drivers)
I'd tempted to deliberately not provide this convenience function and instead
just use ACCESS_PRIVATE() directly in iio_push_to_buffers_with_timestamp()

Nice work. Particularly by highlighting some 'odd corners' in drivers that
probably make no real sense to keep ;)

Jonathan


>  }
>  
>  ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals);