linux-kernel - Re: [PATCH v2] iio: proximity: vl53l0x: Fix return value check of wait_for_completion

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Date:   Sat, 16 Apr 2022 14:59:06 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Miaoqian Lin <linmq006@...il.com>
Cc:     Song Qiang <songqiang1304521@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Ivan Drobyshevskyi <drobyshevskyi@...il.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: proximity: vl53l0x:  Fix return value check of
 wait_for_completion_timeout

On Tue, 12 Apr 2022 06:42:09 +0000
Miaoqian Lin <linmq006@...il.com> wrote:

> wait_for_completion_timeout() returns unsigned long not int.
> It returns 0 if timed out, and positive if completed.
> The check for <= 0 is ambiguous and should be == 0 here
> indicating timeout which is the only error case.
> 
> Fixes: 3cef2e31b54b ("iio: proximity: vl53l0x: Add IRQ support")
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
Hi,

Applied to the togreg branch of iio.git ready for the next
merge window. I'm not rushing this in because it's removing pointless
and misleading code rather than fixing a bug as such.

Thanks,

Jonathan

> ---
> Changes in v2:
> - add driver name in patch subject.
> ---
>  drivers/iio/proximity/vl53l0x-i2c.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/proximity/vl53l0x-i2c.c b/drivers/iio/proximity/vl53l0x-i2c.c
> index 661a79ea200d..a284b20529fb 100644
> --- a/drivers/iio/proximity/vl53l0x-i2c.c
> +++ b/drivers/iio/proximity/vl53l0x-i2c.c
> @@ -104,6 +104,7 @@ static int vl53l0x_read_proximity(struct vl53l0x_data *data,
>  	u16 tries = 20;
>  	u8 buffer[12];
>  	int ret;
> +	unsigned long time_left;
>  
>  	ret = i2c_smbus_write_byte_data(client, VL_REG_SYSRANGE_START, 1);
>  	if (ret < 0)
> @@ -112,10 +113,8 @@ static int vl53l0x_read_proximity(struct vl53l0x_data *data,
>  	if (data->client->irq) {
>  		reinit_completion(&data->completion);
>  
> -		ret = wait_for_completion_timeout(&data->completion, HZ/10);
> -		if (ret < 0)
> -			return ret;
> -		else if (ret == 0)
> +		time_left = wait_for_completion_timeout(&data->completion, HZ/10);
> +		if (time_left == 0)
>  			return -ETIMEDOUT;
>  
>  		vl53l0x_clear_irq(data);