path: root/Documentation/virt/uml
diff options
authorAnton Ivanov <>2022-01-04 10:44:57 +0000
committerRichard Weinberger <>2022-03-11 10:43:32 +0100
commit6427c165275fe11634862149002c7867f25d02f6 (patch)
tree286675d491639345f0a08f9f79d617dc3c054cb1 /Documentation/virt/uml
parent2a6852cb8ff0c8c1363cac648d68489343813212 (diff)
um: Document dtb command line option
Add documentation for the dtb command line option and the ability to load/parse device trees. Signed-off-by: Anton Ivanov <> Reviewed-by: Vincent Whitchurch <> Signed-off-by: Richard Weinberger <>
Diffstat (limited to 'Documentation/virt/uml')
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/virt/uml/user_mode_linux_howto_v2.rst b/Documentation/virt/uml/user_mode_linux_howto_v2.rst
index 2cafd3c3c6cb..81986fe014d4 100644
--- a/Documentation/virt/uml/user_mode_linux_howto_v2.rst
+++ b/Documentation/virt/uml/user_mode_linux_howto_v2.rst
@@ -1189,6 +1189,26 @@ E.g. ``os_close_file()`` is just a wrapper around ``close()``
which ensures that the userspace function close does not clash
with similarly named function(s) in the kernel part.
+Using UML as a Test Platform
+UML is an excellent test platform for device driver development. As
+with most things UML, "some user assembly may be required". It is
+up to the user to build their emulation environment. UML at present
+provides only the kernel infrastructure.
+Part of this infrastructure is the ability to load and parse fdt
+device tree blobs as used in Arm or Open Firmware platforms. These
+are supplied as an optional extra argument to the kernel command
+ dtb=filename
+The device tree is loaded and parsed at boottime and is accessible by
+drivers which query it. At this moment in time this facility is
+intended solely for development purposes. UML's own devices do not
+query the device tree.
Security Considerations