linux-kernel - Re: [PATCH] iio: adc: mt6360: strengthen return check of mt6360_adc_read

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Message-ID: <5477fb05-d72f-ccc0-1c07-8f2f40d9dde0@wanadoo.fr>
Date:   Sun, 27 Feb 2022 18:01:47 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     jic23@...nel.org, lars@...afoo.de, matthias.bgg@...il.com,
        nathan@...nel.org, ndesaulniers@...gle.com,
        linus.walleij@...aro.org, ardeleanalex@...il.com,
        Tom Rix <trix@...hat.com>
Cc:     linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Tom Rix <trix@...hat.com>
Subject: Re: [PATCH] iio: adc: mt6360: strengthen return check of
 mt6360_adc_read_channel

Le 27/02/2022 à 17:43, trix-H+wXaHxf7aLQT0dZR+AlfA@...lic.gmane.org a 
écrit :
> From: Tom Rix <trix-H+wXaHxf7aLQT0dZR+AlfA@...lic.gmane.org>
> 
> Clang static analysis reports this issue
> mt6360-adc.c:277:20: warning: Assigned value is
>    garbage or undefined
>    data.values[i++] = val;
>                     ^ ~~~
> 
> val is set by a successful call to m6360_adc_read_channel().
> A negative return is checked but within m6360_adc_read_channel,
> a non zero check is done.
> Strengthen the check to non zero.

Hi, my understanding of m6360_adc_read_channel() is that on success, it 
returns IIO_VAL_INT (i.e. 1).

So, I think that with your patch, we will now always fail because 'ret' 
is never 0 at this point.

CJ

> 
> Signed-off-by: Tom Rix <trix-H+wXaHxf7aLQT0dZR+AlfA@...lic.gmane.org>
> ---
>   drivers/iio/adc/mt6360-adc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/mt6360-adc.c b/drivers/iio/adc/mt6360-adc.c
> index 07c0e67683910..9fb6dc305a392 100644
> --- a/drivers/iio/adc/mt6360-adc.c
> +++ b/drivers/iio/adc/mt6360-adc.c
> @@ -269,7 +269,7 @@ static irqreturn_t mt6360_adc_trigger_handler(int irq, void *p)
>   	memset(&data, 0, sizeof(data));
>   	for_each_set_bit(bit, indio_dev->active_scan_mask, indio_dev->masklength) {
>   		ret = mt6360_adc_read_channel(mad, bit, &val);
> -		if (ret < 0) {
> +		if (ret) {
>   			dev_warn(&indio_dev->dev, "Failed to get channel %d conversion val\n", bit);
>   			goto out;
>   		}