Skip to content

Commit 9331e5e

Browse files
glikelyJonathan Corbet
authored and
Jonathan Corbet
committed
efi_stub: update documentation on dtb= parameter
The dtb= parameter is no longer the primary mechanism for providing a devicetree to the kernel. Now either firmware or the boot selector (ex. Grub) should provide the devicetree and dtb= should only be used for debug or when using firmware that doesn't understand DT. Update the EFI stub documentation to reflect the current usage. Signed-off-by: Grant Likely <[email protected]> Reviewed-by: Alexander Graf <[email protected]> Acked-by: Leif Lindholm <[email protected]> Acked-by: Olof Johansson <[email protected]> Acked-by: Ard Biesheuvel <[email protected]> Signed-off-by: Jonathan Corbet <[email protected]>
1 parent 2f4830e commit 9331e5e

File tree

1 file changed

+14
-3
lines changed

1 file changed

+14
-3
lines changed

Documentation/efi-stub.txt

+14-3
Original file line numberDiff line numberDiff line change
@@ -83,7 +83,18 @@ is passed to bzImage.efi.
8383
The "dtb=" option
8484
-----------------
8585

86-
For the ARM and arm64 architectures, we also need to be able to provide a
87-
device tree to the kernel. This is done with the "dtb=" command line option,
88-
and is processed in the same manner as the "initrd=" option that is
86+
For the ARM and arm64 architectures, a device tree must be provided to
87+
the kernel. Normally firmware shall supply the device tree via the
88+
EFI CONFIGURATION TABLE. However, the "dtb=" command line option can
89+
be used to override the firmware supplied device tree, or to supply
90+
one when firmware is unable to.
91+
92+
Please note: Firmware adds runtime configuration information to the
93+
device tree before booting the kernel. If dtb= is used to override
94+
the device tree, then any runtime data provided by firmware will be
95+
lost. The dtb= option should only be used either as a debug tool, or
96+
as a last resort when a device tree is not provided in the EFI
97+
CONFIGURATION TABLE.
98+
99+
"dtb=" is processed in the same manner as the "initrd=" option that is
89100
described above.

0 commit comments

Comments
 (0)