linux-kernel - Re: [PATCH v7 2/2] staging: rtl8723bs: Use % 4096 instead of & 0xfff

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Message-ID: <Z_U2ohN4wbbOtepn@smile.fi.intel.com>
Date: Tue, 8 Apr 2025 17:45:54 +0300
From: Andy Shevchenko <andy@...nel.org>
To: Abraham Samuel Adekunle <abrahamadekunle50@...il.com>
Cc: outreachy@...ts.linux.dev, julia.lawall@...ia.fr,
	gregkh@...uxfoundation.org, linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org, david.laight.linux@...il.com,
	dan.carpenter@...aro.org
Subject: Re: [PATCH v7 2/2] staging: rtl8723bs: Use % 4096 instead of & 0xfff

On Tue, Apr 08, 2025 at 01:31:42PM +0000, Abraham Samuel Adekunle wrote:
> The sequence number is constrained to a range of [0, 4095], which
> is a total of 4096 values. The bitmask operation using `& 0xfff` is
> used to perform this wrap-around. While this is functionally correct,
> it obscures the intended semantic of a 4096-based wrap.
> 
> Using a modulo operation `% 4096u` makes the wrap-around logic
> explicit and easier to understand. It clearly signals that the
> sequence number cycles through a range of 4096 values.
> It also makes the code robust against potential changes of the 4096
> upper limit, especially when it becomes a non power of 2 value while

power-of-2

> the AND(&) works solely for power of 2 values.

power-of-2

> The use of `% 4096u` also guarantees that the modulo operation is
> performed with unsigned arithmetic, preventing potential issues with
> the signed types.

Reviewed-by: Andy Shevchenko <andy@...nel.org>

-- 
With Best Regards,
Andy Shevchenko