mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-13 14:53:06 +00:00
830b5936c3
Update the extension command title for consistency with other commands. Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
111 lines
2.9 KiB
ReStructuredText
111 lines
2.9 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
|
|
.. Copyright 2021, Kory Maincent <kory.maincent@bootlin.com>
|
|
|
|
extension command
|
|
=================
|
|
|
|
Synopsis
|
|
--------
|
|
|
|
::
|
|
|
|
extension scan
|
|
extension list
|
|
extension apply <extension number|all>
|
|
|
|
Description
|
|
-----------
|
|
|
|
The "extension" command proposes a generic U-Boot mechanism to detect
|
|
extension boards connected to the HW platform, and apply the appropriate
|
|
Device Tree overlays depending on the detected extension boards.
|
|
|
|
The "extension" command comes with three sub-commands:
|
|
|
|
- "extension scan" makes the generic code call the board-specific
|
|
extension_board_scan() function to retrieve the list of detected
|
|
extension boards.
|
|
|
|
- "extension list" allows to list the detected extension boards.
|
|
|
|
- "extension apply <number>|all" allows to apply the Device Tree
|
|
overlay(s) corresponding to one, or all, extension boards
|
|
|
|
The latter requires two environment variables to exist:
|
|
|
|
- extension_overlay_addr: the RAM address where to load the Device
|
|
Tree overlays
|
|
|
|
- extension_overlay_cmd: the U-Boot command to load one overlay.
|
|
Indeed, the location and mechanism to load DT overlays is very setup
|
|
specific.
|
|
|
|
In order to enable this mechanism, board-specific code must implement
|
|
the extension_board_scan() function that fills in a linked list of
|
|
"struct extension", each describing one extension board. In addition,
|
|
the board-specific code must select the SUPPORT_EXTENSION_SCAN Kconfig
|
|
boolean.
|
|
|
|
Usage example
|
|
-------------
|
|
|
|
1. Make sure your devicetree is loaded and set as the working fdt tree.
|
|
|
|
::
|
|
|
|
=> run loadfdt
|
|
=> fdt addr $fdtaddr
|
|
|
|
2. Prepare the environment variables
|
|
|
|
::
|
|
|
|
=> setenv extension_overlay_addr 0x88080000
|
|
=> setenv extension_overlay_cmd 'load mmc 0:1 ${extension_overlay_addr} /boot/${extension_overlay_name}'
|
|
|
|
3. Detect the plugged extension board
|
|
|
|
::
|
|
|
|
=> extension scan
|
|
|
|
4. List the plugged extension board information and the devicetree
|
|
overlay name
|
|
|
|
::
|
|
|
|
=> extension list
|
|
|
|
5. Apply the appropriate devicetree overlay
|
|
|
|
For apply the selected overlay:
|
|
|
|
::
|
|
|
|
=> extension apply 0
|
|
|
|
For apply all the overlays:
|
|
|
|
::
|
|
|
|
=> extension apply all
|
|
|
|
Simple extension_board_scan function example
|
|
--------------------------------------------
|
|
|
|
.. code-block:: c
|
|
|
|
int extension_board_scan(struct list_head *extension_list)
|
|
{
|
|
struct extension *extension;
|
|
|
|
extension = calloc(1, sizeof(struct extension));
|
|
snprintf(extension->overlay, sizeof(extension->overlay), "overlay.dtbo");
|
|
snprintf(extension->name, sizeof(extension->name), "extension board");
|
|
snprintf(extension->owner, sizeof(extension->owner), "sandbox");
|
|
snprintf(extension->version, sizeof(extension->version), "1.1");
|
|
snprintf(extension->other, sizeof(extension->other), "Extension board information");
|
|
list_add_tail(&extension->list, extension_list);
|
|
|
|
return 1;
|
|
}
|