linux-kernel - Re: [PATCH] drm/drm_vblank.c: avoid unsigned int to signed int cast

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Message-ID: <4c9c0897-5e3a-1469-3d87-ff7723ac160c@189.cn>
Date:   Tue, 23 May 2023 12:26:32 +0800
From:   Sui Jingfeng <15330273260@....cn>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        David Laight <David.Laight@...LAB.COM>,
        Sui Jingfeng <suijingfeng@...ngson.cn>,
        Li Yi <liyi@...ngson.cn>
Cc:     Thomas Zimmermann <tzimmermann@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "loongson-kernel@...ts.loongnix.cn" 
        <loongson-kernel@...ts.loongnix.cn>
Subject: Re: [PATCH] drm/drm_vblank.c: avoid unsigned int to signed int cast

Hi,

On 2023/5/22 19:29, Jani Nikula wrote:
> In general, do not use unsigned types in arithmethic to avoid negative
> values, because most people will be tripped over by integer promotion
> rules, and you'll get negative values anyway.


Here I'm sure about this,

but there are plenty unsigned types arithmetic in the kernel.

take kmalloc_array() function as an example in /tools/virto/linux/kernel.h


static inline void *kmalloc_array(unsigned n, size_t s, gfp_t gfp)
{
     return kmalloc(n * s, gfp);
}


NOTE that *size_t* is an unsigned integral data type.