linux-kernel - Re: [PATCH v3 4/4] x86/CPU/AMD: Print the reason for the last reset

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Message-ID: <20250411125050.GEZ_kQKtYBfEMDQuXU@fat_crate.local>
Date: Fri, 11 Apr 2025 14:50:50 +0200
From: Borislav Petkov <bp@...en8.de>
To: Mario Limonciello <superm1@...nel.org>
Cc: Jean Delvare <jdelvare@...e.com>, Andi Shyti <andi.shyti@...nel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Jonathan Corbet <corbet@....net>,
	Mario Limonciello <mario.limonciello@....com>,
	Yazen Ghannam <yazen.ghannam@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>,
	Shyam Sundar S K <Shyam-sundar.S-k@....com>,
	Hans de Goede <hdegoede@...hat.com>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:I2C/SMBUS CONTROLLER DRIVERS FOR PC" <linux-i2c@...r.kernel.org>,
	"open list:AMD PMC DRIVER" <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH v3 4/4] x86/CPU/AMD: Print the reason for the last reset

On Fri, Apr 11, 2025 at 07:12:24AM -0500, Mario Limonciello wrote:
> The idea was to walk all the bits and pick the first one that has a string
> associated with it.  I was finding that sometimes the reserved bits are set
> which would get you a NULL pointer deref.

Uff, that needs a comment at least.

But you can write it a lot simpler instead:

	for (i = 0; i <= ARRAY_SIZE(s5_reset_reason_txt); i++) {
		if (!(value & BIT(i)))
			continue;

		if (s5_reset_reason_txt[i])
			break;
	}

Simple loop, simple statements and all easy. :-)

> Right; I was worried about that too but find_next_bit() will return the size
> argument when it doesn't find anything.
> 
> So that should be s5_reset_reason_txt[32] which has the "Unknown" string.

Yeah, that definitely needs a comment above it.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette