linux-kernel - Re: [BUG RFC] iio: pressure: zpa2326: incorrect condition or inconsistent return handling

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Message-ID: <alpine.DEB.2.20.1705031340050.29003@vps.pmeerw.net>
Date:   Wed, 3 May 2017 13:42:08 +0200 (CEST)
From:   Peter Meerwald-Stadler <pmeerw@...erw.net>
To:     Nicholas Mc Guire <der.herr@...r.at>
cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        simran singhal <singhalsimran0@...il.com>,
        Gregor Boirie <gregor.boirie@...rot.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG RFC] iio: pressure: zpa2326: incorrect condition or
 inconsistent return handling

Hello,

> wait_for_completion_interruptible_timeout() returns -ERESTARTSYS, 0 or
> remaining time in jiffies (atleast 1), thus the if (ret != -ERESTARTSYS)
> case here is unreachable. 

if is not unreachable, there is a ret = -ETIME above it
 
> As it is not clear from the warn message if this should simply be changed
> to if (ret == -ERESTARTSYS), this needs a review by someone that knows
> the intent of this condition. In any case the current treatment of the
> return value of wait_for_completion_interruptible_timeout() is inconsistent
> with the specification of the same.

the intention of the code is not very clear, I agree

"no one shot interrupt" should probably be printed for the -ETIME case, 
i.e. when a timeout occurs
 
> Also wait_for_completion_interruptible_timeout() returns a long not int.

true
 
> Problem was introduced in commit 03b262f2bbf4 ("iio:pressure: initial zpa2326 barometer support")
> 
>  drivers/iio/pressure/zpa2326.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/pressure/zpa2326.c b/drivers/iio/pressure/zpa2326.c
> index e58a0ad..80ca6ec 100644
> --- a/drivers/iio/pressure/zpa2326.c
> +++ b/drivers/iio/pressure/zpa2326.c
> @@ -872,35 +872,35 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev   *indio_dev,
>  
>  	ret = wait_for_completion_interruptible_timeout(
>  		&private->data_ready, ZPA2326_CONVERSION_JIFFIES);
>  	if (ret > 0)
>  		/*
>  		 * Interrupt handler completed before timeout: return operation
>  		 * status.
>  		 */
>  		return private->result;
>  
>  	/* Clear all interrupts just to be sure. */
>  	regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
>  
>  	if (!ret)
>  		/* Timed out. */
>  		ret = -ETIME;
>  
> -	if (ret != -ERESTARTSYS)
> +	if (ret == -ERESTARTSYS)
>  		zpa2326_warn(indio_dev, "no one shot interrupt occurred (%d)",
>  			     ret);
>  
>  	return ret;
>  }
>  
>  static int zpa2326_init_managed_irq(struct device          *parent,
>  				    struct iio_dev         *indio_dev,
>  				    struct zpa2326_private *private,
>  				    int                     irq)
>  {
>  	int err;
>  
>  	private->irq = irq;
>  
>  	if (irq <= 0) {
>  		/*
> 

-- 

Peter Meerwald-Stadler
Mobile: +43 664 24 44 418