linux-kernel - [x86 question] invalid conversion of bootloader_type and bootloader

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Message-id: <16419793.126861392271147946.JavaMail.weblogic@epv6ml15>
Date:	Thu, 13 Feb 2014 05:59:08 +0000 (GMT)
From:	Jongman Heo <jongman.heo@...sung.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [x86 question] invalid conversion of bootloader_type and
 bootloader_version ??

Hi, all,

While looking at x86 boot code (arch/x86/kernel/setup.c), I got confused due to bootloader_type and bootloader_version conversion.

I've only checked GRUB and U-Boot bootloader code.

1. GRUB 2
    type_of_loader setting = 0x72
-> bootloader_type = 0x72, bootloader_version = 0x2

2. U-Boot
    type_of_loader setting = 0x8
-> bootloader_type = 0x8, bootloader_version = 0x8

3. example in Documentation/x86/boot.txt
    type_of_loader  = 0xE4, ext_loader_type = 0x05, ext_loader_ver = 0x23, for T = 0x15, V = 0x234
-> bootloader_type = 0x154, bootloader_version = 0x234

So, for GRUB 2 and the example bootloader, T != bootloader_type. 
Is this intended?
First I thought that bootloader_type and bootloader_version should match with T and V configured in the bootloader. 

This would not bring any real world issue, but I'm just curious.

Regards,
Jongman Heo.