linux-kernel - Re: [PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR

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Message-ID: <56BAA27A.9050605@roeck-us.net>
Date:	Tue, 9 Feb 2016 18:37:46 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Arnd Bergmann <arnd@...db.de>, linux-arm-kernel@...ts.infradead.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Baruch Siach <baruch@...s.co.il>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, Jiri Slaby <jslaby@...e.com>,
	kernel-testers@...r.kernel.org, Andrzej Hajda <a.hajda@...sung.com>
Subject: Re: [PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR_VALUE

On 02/09/2016 07:26 AM, Arnd Bergmann wrote:
> On Tuesday 09 February 2016 07:08:59 Guenter Roeck wrote:
>> IS_ERR_VALUE() assumes that its parameter is an unsigned long.
>> It can not be used to check if an unsigned int reflects an error.
>> Doing so can result in the following build warning.
>>
>> drivers/tty/serial/digicolor-usart.c: In function ‘digicolor_uart_probe’:
>> include/linux/err.h:21:38: warning:
>>          comparison is always false due to limited range of data type
>> drivers/tty/serial/digicolor-usart.c:485:6: note:
>>          in expansion of macro ‘IS_ERR_VALUE’
>>
>> If that warning is seen, an error return from platform_get_irq() is missed.
>>
>>
>
> The patch looks correct to me, but what compiler version and which kernel
> tree is it that triggered the warning?
>
> Andrzej Hajda just modified the definition of IS_ERR_VALUE(), and the
> changes are still under discussion, but I don't see that warning with
> any of the versions.
>
I see it with gcc 5.1 and 5.2 (and W=1). I did not see / notice Andrzej's patch.

I agree that fixing the problem in IS_ERR_VALUE() is preferrable.

Guenter