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

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Date:	Tue, 09 Feb 2016 16:26:38 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Guenter Roeck <linux@...ck-us.net>,
	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 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.

	Arnd