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"Das U-Boot" Source Tree
1.. SPDX-License-Identifier: GPL-2.0+:
2
3Script Bootmeth
4===============
5
6This bootmeth provides a way to locate and run a script on a block or network
7device. It can also support SPI flash.
8
9For a block device the file is read from the selected partition, which must use
10a supported filesystem. The subdirectory to search in is defined by the bootstd
11list of prefixes (``{"/", "/boot"}`` by default) and can be adjust with the
12`filename-prefixes` property in the bootstd device.
13
14For a network device, the filename is obtained from the `boot_script_dhcp`
15environment variable and the file is read using tftp. It must be in the
16top-level directory of the tftp server.
17
18In either case (file or network), the bootmeth searches for the file and creates
19a bootflow if found. The bootmeth searches for "boot.scr.uimg" first, then
20"boot.scr" if not found.
21
22For SPI flash, a script is read from flash using the offset provided by the
23"script_offset_f" environment variable.
24
25Some attempt is made to identify the Operating System: so far this only detects
26an `Armbian <https://www.armbian.com>`_
27distro. For block devices, if a file called "boot.bmp" exists in the same
28directory then it is used as the bootflow logo.
29
30When the bootflow is booted, the bootmeth sets these environment variables:
31
32 devtype
33 device type (e.g. "usb", "mmc", "ethernet" or "spi_flash")
34
35 devnum
36 device number, corresponding to the device 'sequence' number
37 ``dev_seq(dev)``
38
39 distro_bootpart
40 (block devices only) partition number on the device (numbered from 1)
41
42 prefix
43 prefix used to find the file
44
45 mmc_bootdev
46 device number (same as `devnum`), set for sunxi mmc devices only
47
48The script file must be a FIT or a legacy uImage. It is loaded into memory and
49executed.
50
51The compatible string "u-boot,script" is used for the driver. It is present
52if `CONFIG_BOOTMETH_SCRIPT` is enabled.