linux-kernel - Re: [PATCH] iio: adc: mcp3911: simplify code with guard macro

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Date:   Sun, 26 Nov 2023 18:09:35 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Kent Gustavsson <kent@...oris.se>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: adc: mcp3911: simplify code with guard macro

On Sat, 25 Nov 2023 19:57:24 +0100
Marcus Folkesson <marcus.folkesson@...il.com> wrote:

> Use the guard(mutex) macro for handle mutex lock/unlocks.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>
Hi Marcus,

Great to see this being used, but there is a little more you can do
here to take advantage fully.

> ---
>  drivers/iio/adc/mcp3911.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
> index 974c5bd923a6..85bb13eb6f3b 100644
> --- a/drivers/iio/adc/mcp3911.c
> +++ b/drivers/iio/adc/mcp3911.c
> @@ -7,6 +7,7 @@
>   */
>  #include <linux/bitfield.h>
>  #include <linux/bits.h>
> +#include <linux/cleanup.h>
>  #include <linux/clk.h>
>  #include <linux/delay.h>
>  #include <linux/err.h>
> @@ -168,7 +169,7 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
>  	struct mcp3911 *adc = iio_priv(indio_dev);
>  	int ret = -EINVAL;
>  
> -	mutex_lock(&adc->lock);
> +	guard(mutex)(&adc->lock);
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
>  		ret = mcp3911_read(adc,
> @@ -207,7 +208,6 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
>  	}
>  
>  out:
> -	mutex_unlock(&adc->lock);
>  	return ret;
No point in having the label down here after the change. Just return directly
wherever you see an error.

Same for other cases.

>  }
>  
> @@ -218,7 +218,7 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
>  	struct mcp3911 *adc = iio_priv(indio_dev);
>  	int ret = -EINVAL;
>  
> -	mutex_lock(&adc->lock);
> +	guard(mutex)(&adc->lock);
>  	switch (mask) {
>  	case IIO_CHAN_INFO_SCALE:
>  		for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
> @@ -263,7 +263,6 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
>  	}
>  
>  out:
> -	mutex_unlock(&adc->lock);
>  	return ret;
>  }
>  
> @@ -350,7 +349,7 @@ static irqreturn_t mcp3911_trigger_handler(int irq, void *p)
>  	int i = 0;
>  	int ret;
>  
> -	mutex_lock(&adc->lock);
> +	guard(mutex)(&adc->lock);
>  	adc->tx_buf = MCP3911_REG_READ(MCP3911_CHANNEL(0), adc->dev_addr);
>  	ret = spi_sync_transfer(adc->spi, xfer, ARRAY_SIZE(xfer));
>  	if (ret < 0) {
> @@ -368,7 +367,6 @@ static irqreturn_t mcp3911_trigger_handler(int irq, void *p)
>  	iio_push_to_buffers_with_timestamp(indio_dev, &adc->scan,
>  					   iio_get_time_ns(indio_dev));
>  out:
> -	mutex_unlock(&adc->lock);
>  	iio_trigger_notify_done(indio_dev->trig);
>  
>  	return IRQ_HANDLED;
> 
> ---
> base-commit: ffc253263a1375a65fa6c9f62a893e9767fbebfa
> change-id: 20231125-mcp3911-guard-866591e2c947
> 
> Best regards,