summaryrefslogtreecommitdiffstats
path: root/Documentation/arch/x86/booting-dt.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/arch/x86/booting-dt.rst')
-rw-r--r--Documentation/arch/x86/booting-dt.rst21
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/arch/x86/booting-dt.rst b/Documentation/arch/x86/booting-dt.rst
new file mode 100644
index 0000000000..b089ffd56e
--- /dev/null
+++ b/Documentation/arch/x86/booting-dt.rst
@@ -0,0 +1,21 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+DeviceTree Booting
+------------------
+
+ 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/arch/x86/boot.rst
+ The physical pointer to the device-tree block 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.