| .. SPDX-License-Identifier: GPL-2.0+ |
| |
| fdt command |
| =========== |
| |
| Synopis |
| ------- |
| |
| :: |
| |
| fdt addr [-cq] [addr [len]] |
| |
| Description |
| ----------- |
| |
| The fdt command provides access to flat device tree blobs in memory. It has |
| many subcommands, some of which are not documented here. |
| |
| Flags: |
| |
| -c |
| Select the control FDT (otherwise the working FDT is used). |
| -q |
| Don't display errors |
| |
| The control FDT is the one used by U-Boot itself to control various features, |
| including driver model. This should only be changed if you really know what you |
| are doing, since once U-Boot starts it maintains pointers into the FDT from the |
| various driver model data structures. |
| |
| The working FDT is the one passed to the Operating System when booting. This |
| can be freely modified, so far as U-Boot is concerned, since it does not affect |
| U-Boot's operation. |
| |
| fdt addr |
| ~~~~~~~~ |
| |
| With no arguments, this shows the address of the current working or control |
| FDT. |
| |
| If the `addr` argument is provided, then this sets the address of the working or |
| control FDT to the provided address. |
| |
| If the `len` argument is provided, then the device tree is expanded to that |
| size. This can be used to make space for more nodes and properties. It is |
| assumed that there is enough space in memory for this expansion. |
| |
| Example |
| ------- |
| |
| Get the control address and copy that FDT to free memory:: |
| |
| => fdt addr -c |
| Control fdt: 0aff9fd0 |
| => cp.b 0aff9fd0 10000 10000 |
| => md 10000 4 |
| 00010000: edfe0dd0 5b3d0000 78000000 7c270000 ......=[...x..'| |
| |
| The second word shows the size of the FDT. Now set the working FDT to that |
| address and expand it to 0xf000 in size:: |
| |
| => fdt addr 10000 f000 |
| => md 10000 4 |
| 00010000: edfe0dd0 00f00000 78000000 7c270000 ...........x..'| |
| |
| Return value |
| ------------ |
| |
| The return value $? indicates whether the command succeeded. |