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rpi-u-boot-scr: load the kernel from the bootflow device #1635

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rpi-u-boot-scr: load the kernel from the bootflow device #1635

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rpi-u-boot-scr: load the kernel from the bootflow device
wonwondogs Oct 18, 2026
84d705d
Merge branch 'master' into rpi-u-boot-scr-usb-bootflow-device
agherzan Nov 2, 2026
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2 changes: 1 addition & 1 deletion docs/extra-build-config.md
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,7 @@ By default SD card media is used as boot media.
To switch the boot media from SD card to USB memory, the following variables are supported
in local.conf: `CMDLINE_ROOT_PARTITION` and `BOOT_MEDIA`.
The default value of `CMDLINE_ROOT_PARTITION` is "/dev/mmcblk0p2" to mount SD card. If you want to mount USB memory partition, set CMDLINE_ROOT_PARTITION to "/dev/sda2".
`BOOT_MEDIA` allows `mmc` and `usb`. The "mmc" is required to load an image from the SD card, following the u-boot specification. Similarly, if you want to load a boot image file from USB memory, set BOOT_MEDIA to "usb".
`BOOT_MEDIA` allows `mmc` and `usb`. When U-Boot bootflow runs the boot script, the kernel is loaded from the device and partition holding the script. `BOOT_MEDIA` (device 0, partition 1) is only used when `devtype`, `devnum` and `distro_bootpart` are not set, for example when sourcing the script manually.

For example, if you want to use USB boot, please define
the following parameters in your local.conf file.
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17 changes: 15 additions & 2 deletions recipes-bsp/rpi-u-boot-scr/files/boot.cmd.in
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@@ -1,4 +1,17 @@
fdt addr ${fdt_addr} && fdt get value bootargs /chosen bootargs
fatload @@BOOT_MEDIA@@ 0:1 ${kernel_addr_r} @@KERNEL_IMAGETYPE@@
if test ! -e @@BOOT_MEDIA@@ 0:1 uboot.env; then saveenv; fi;

# Load the kernel from the bootflow device; fall back to BOOT_MEDIA 0:1.
if test -n "${devtype}" -a -n "${devnum}" -a -n "${distro_bootpart}"; then
fatload ${devtype} ${devnum}:${distro_bootpart} ${kernel_addr_r} @@KERNEL_IMAGETYPE@@
else
fatload @@BOOT_MEDIA@@ 0:1 ${kernel_addr_r} @@KERNEL_IMAGETYPE@@
fi

# uboot.env lives on mmc 0:1. Only create it when booted from there (not
# on another image's SD card) and without the per-boot bootflow variables.
if test "${devtype}" = mmc -a "${devnum}" = 0 -a "${distro_bootpart}" = 1 -a ! -e mmc 0:1 uboot.env; then
env delete devtype devnum distro_bootpart prefix
saveenv
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fi

@@KERNEL_BOOTCMD@@ ${kernel_addr_r} - ${fdt_addr}
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