linux-kernel - Re: [PATCH] carl9170: Fix error return -EAGAIN if not started

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Message-ID: <382b719f-f14e-2963-284d-c0b38dedc4ae@canonical.com>
Date:   Fri, 8 Oct 2021 08:31:29 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Christian Lamparter <chunkeey@...glemail.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "John W . Linville" <linville@...driver.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] carl9170: Fix error return -EAGAIN if not started

On 08/10/2021 06:58, Dan Carpenter wrote:
> On Fri, Oct 08, 2021 at 01:15:58AM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> There is an error return path where the error return is being
>> assigned to err rather than count and the error exit path does
>> not return -EAGAIN as expected. Fix this by setting the error
>> return to variable count as this is the value that is returned
>> at the end of the function.
>>
>> Addresses-Coverity: ("Unused value")
>> Fixes: 00c4da27a421 ("carl9170: firmware parser and debugfs code")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>   drivers/net/wireless/ath/carl9170/debug.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/wireless/ath/carl9170/debug.c b/drivers/net/wireless/ath/carl9170/debug.c
>> index bb40889d7c72..f163c6bdac8f 100644
>> --- a/drivers/net/wireless/ath/carl9170/debug.c
>> +++ b/drivers/net/wireless/ath/carl9170/debug.c
>> @@ -628,7 +628,7 @@ static ssize_t carl9170_debugfs_bug_write(struct ar9170 *ar, const char *buf,
>>   
>>   	case 'R':
>>   		if (!IS_STARTED(ar)) {
>> -			err = -EAGAIN;
>> +			count = -EAGAIN;
>>   			goto out;
> 
> This is ugly.  The bug wouldn't have happened with a direct return, it's
> only the goto out which causes it.  Better to replace all the error
> paths with direct returns.  There are two other direct returns so it's
> not like a new thing...

Yep, I agree it was ugly, I was trying to keep to the coding style and 
reduce the patch delta size. I can do a V2 if the maintainers deem it's 
a cleaner solution.

> 
> Goto out on the success path is fine here, though.

Yep. I believe that a goto to one exit return point (may possibly?) make 
the code smaller rather than a sprinkling of returns in a function, so 
I'm never sure if this is a win or not with these kind of cases.

Colin
> 
> regards,
> dan carpenter
>