0001 .. SPDX-License-Identifier: GPL-2.0
0002
0003 DeviceTree Booting
0004 ------------------
0005
0006 There is one single 32bit entry point to the kernel at code32_start,
0007 the decompressor (the real mode entry point goes to the same 32bit
0008 entry point once it switched into protected mode). That entry point
0009 supports one calling convention which is documented in
0010 Documentation/x86/boot.rst
0011 The physical pointer to the device-tree block is passed via setup_data
0012 which requires at least boot protocol 2.09.
0013 The type filed is defined as
0014
0015 #define SETUP_DTB 2
0016
0017 This device-tree is used as an extension to the "boot page". As such it
0018 does not parse / consider data which is already covered by the boot
0019 page. This includes memory size, reserved ranges, command line arguments
0020 or initrd address. It simply holds information which can not be retrieved
0021 otherwise like interrupt routing or a list of devices behind an I2C bus.
