linux-kernel - Re: [PATCH v2] leds: bcm6328: Replace divide condition with comparison for shift value

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Message-ID: <Z0IzQlsP6OMCcXRB@surfacebook.localdomain>
Date: Sat, 23 Nov 2024 21:55:46 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Dipendra Khadka <kdipendra88@...il.com>
Cc: lee@...nel.org, pavel@....cz, linux-leds@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] leds: bcm6328: Replace divide condition with
 comparison for shift value

Sat, Oct 19, 2024 at 07:33:01AM +0000, Dipendra Khadka kirjoitti:
> Fixes the following Smatch warnings:
> drivers/leds/leds-bcm6328.c:116 bcm6328_led_mode() warn: replace divide condition 'shift / 16' with 'shift >= 16'
> drivers/leds/leds-bcm6328.c:360 bcm6328_led() warn: replace divide condition 'shift / 16' with 'shift >= 16'

As discussed with Dan (author of smatch), these warnings make no much sense as
"division" by power-of-two numbers in modern world (ISAs, compilers, etc) most
unlikely become a real division instruction with all bad consequences. Even
though, some ISAs can optimize cases where foo / 16; foo % 16 goes together and
this change may break that.

So, please, consider not to send such changes in the future because at least
they are just noise, at most might add a (micro-)rgressions.

https://lore.kernel.org/linux-gpio/20241112201659.16785-1-surajsonawane0215@gmail.com/
https://lore.kernel.org/all/20241121105838.4073659-4-andriy.shevchenko@linux.intel.com/

-- 
With Best Regards,
Andy Shevchenko