[PATCH] Add 'bootsource' /chosen property

[Daniel Golle]

Hi Quentin,

On 10 February 2025 16:25:23 UTC, Quentin Schulz <quentin.schulz at cherry.de> wrote:
> [...]
>What I can say from glancing at the code is that for Rockchip they do the following:
>
>Register a bootsource type (e.g. MMC, SPI, I2C, USB, etc...), a bootsource instance of that type (e.g. MMC0, SPI3, I2C7, ...). The mapping between what the ROM says the device is vs what it is in the DT is done in their Barebox-specific DT via this custom prop in /chosen:
>
>barebox,bootsource-<bootsourcetype><bootsourceinstance> = &label;  # à-la /aliases
>
>This gets read and resolved and then inserted as
>
>/chosen/bootsource = "/some/path"
>
>into the kernel DT.

We are doing something quite similar downsream at openwrt.org for MediaTek router SoCs, see for example:

https://github.com/openwrt/openwrt/blob/main/package/boot/uboot-mediatek/patches/310-mt7988-select-rootdisk.patch

https://github.com/openwrt/openwrt/blob/main/target/linux/mediatek/files-6.6/arch/arm64/boot/dts/mediatek/mt7988a-bananapi-bpi-r4.dtsi#L32

https://github.com/openwrt/openwrt/blob/main/target/linux/mediatek/files-6.6/arch/arm64/boot/dts/mediatek/mt7988a-bananapi-bpi-r4-emmc.dtso#L60


Of course we could use the standard "bootsource" property instead, but having a way to reference the volume or partition used as rootfs instead of just passing a referencd to a physical device is advantagous...