linux-kernel - Re: [PATCH RFC 5/6] iio: health: max30102: Use cleanup.h for IIO locks

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Message-ID: <f96694db-2ad5-46d3-a380-cba3eaa2de2f@baylibre.com>
Date: Wed, 3 Dec 2025 15:52:43 -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 RFC 5/6] iio: health: max30102: Use cleanup.h for IIO
 locks

On 12/3/25 1:18 PM, Kurt Borja wrote:
> Simplify and drop "hacky" busy-waiting code in max30102_read_raw() by
> using scoped_guard().
> 
> Signed-off-by: Kurt Borja <kuurtb@...il.com>
> ---
>  drivers/iio/health/max30102.c | 24 +++++++-----------------
>  1 file changed, 7 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iio/health/max30102.c b/drivers/iio/health/max30102.c
> index 678720102f2b..c642842cb5fb 100644
> --- a/drivers/iio/health/max30102.c
> +++ b/drivers/iio/health/max30102.c
> @@ -24,6 +24,7 @@
>  #include <linux/iio/iio.h>
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/kfifo_buf.h>
> +#include <linux/cleanup.h>
>  
>  #define MAX30102_DRV_NAME	"max30102"
>  #define MAX30102_PART_NUMBER	0x15
> @@ -468,6 +469,7 @@ static int max30102_read_raw(struct iio_dev *indio_dev,
>  {
>  	struct max30102_data *data = iio_priv(indio_dev);
>  	int ret = -EINVAL;
> +	bool direct_en;
>  
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
> @@ -475,25 +477,13 @@ static int max30102_read_raw(struct iio_dev *indio_dev,
>  		 * Temperature reading can only be acquired when not in
>  		 * shutdown; leave shutdown briefly when buffer not running
>  		 */
> -any_mode_retry:
> -		if (!iio_device_claim_buffer(indio_dev)) {
> -			/*
> -			 * This one is a *bit* hacky. If we cannot claim buffer
> -			 * mode, then try direct mode so that we make sure
> -			 * things cannot concurrently change. And we just keep
> -			 * trying until we get one of the modes...
> -			 */
> -			if (!iio_device_claim_direct(indio_dev))
> -				goto any_mode_retry;
> +		scoped_guard(iio_device_claim, indio_dev) {

scoped_guard() is sketchy in switch statements because there is
a hidden for loop. If someone came along later and put a break;
inside of the scope, it would break out of the hidden for loop
rather than the apparent switch case!

Besides that, it adds extra indent that we could avoid.

> +			direct_en = !iio_buffer_enabled(indio_dev);
>  
> -			ret = max30102_get_temp(data, val, true);
> -			iio_device_release_direct(indio_dev);
> -		} else {
> -			ret = max30102_get_temp(data, val, false);
> -			iio_device_release_buffer(indio_dev);
> +			ret = max30102_get_temp(data, val, direct_en);
> +			if (ret)
> +				return ret;
>  		}
> -		if (ret)
> -			return ret;
>  
>  		ret = IIO_VAL_INT;
>  		break;
> 

I would write the whole function like this:

static int max30102_read_raw(struct iio_dev *indio_dev,
			     struct iio_chan_spec const *chan,
			     int *val, int *val2, long mask)
{
	struct max30102_data *data = iio_priv(indio_dev);
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW: {
		/*
		 * Temperature reading can only be acquired when not in
		 * shutdown; leave shutdown briefly when buffer not running
		 */
		guard(iio_device_claim)(indio_dev);
		ret = max30102_get_temp(data, val, !iio_buffer_enabled(indio_dev));
		if (ret)
			return ret;

		return IIO_VAL_INT;
	}
	case IIO_CHAN_INFO_SCALE:
		*val = 1000;  /* 62.5 */
		*val2 = 16;
		return IIO_VAL_FRACTIONAL;
	default:
		return -EINVAL;
	}
}

Could also simplify things further by moving the call to iio_buffer_enabled()
into max30102_get_temp().