linux-kernel - Re: [PATCH 0/1] Slightly relax the type checking done by min() and max().

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Message-ID: <Y4DdQIMiFGk7YYcJ@smile.fi.intel.com>
Date:   Fri, 25 Nov 2022 17:20:32 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        'Joe Perches' <joe@...ches.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 0/1] Slightly relax the type checking done by min() and
 max().

On Fri, Nov 25, 2022 at 03:00:40PM +0000, David Laight wrote:
> The min() and max() defines include a type check to avoid the unexpected
>   behaviour when a negative value is compared against and unsigned value.
> However a lot of code hits this check and uses min_t() to avoid the error.
> Many of these are just plain wrong.
> 
> Those casting to u8 or u16 are particularly suspect, eg:
> drivers/usb/misc/usb251xb.c:528:
> 		hub->max_current_sp = min_t(u8, property_u32 / 2000, 50);

I don't buy this. What's exactly wrong with this code?

-- 
With Best Regards,
Andy Shevchenko