path: root/Documentation/devicetree/booting-without-of.txt
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Diffstat (limited to 'Documentation/devicetree/booting-without-of.txt')
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diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
index 28b1c9d3d351..55fd2623445b 100644
--- a/Documentation/devicetree/booting-without-of.txt
+++ b/Documentation/devicetree/booting-without-of.txt
@@ -13,6 +13,7 @@ Table of Contents
I - Introduction
1) Entry point for arch/powerpc
+ 2) Entry point for arch/x86
II - The DT block format
1) Header
@@ -225,6 +226,25 @@ it with special cases.
cannot support both configurations with Book E and configurations
with classic Powerpc architectures.
+2) Entry point for arch/x86
+ There is one single 32bit entry point to the kernel at code32_start,
+ the decompressor (the real mode entry point goes to the same 32bit
+ entry point once it switched into protected mode). That entry point
+ supports one calling convention which is documented in
+ Documentation/x86/boot.txt
+ The physical pointer to the device-tree block (defined in chapter II)
+ is passed via setup_data which requires at least boot protocol 2.09.
+ The type filed is defined as
+ #define SETUP_DTB 2
+ This device-tree is used as an extension to the "boot page". As such it
+ does not parse / consider data which is already covered by the boot
+ page. This includes memory size, reserved ranges, command line arguments
+ or initrd address. It simply holds information which can not be retrieved
+ otherwise like interrupt routing or a list of devices behind an I2C bus.
II - The DT block format