Switch from u-boot scripts to generated extlinux.conf

Features

It makes device packages simpler and applies UUIDs to cmdline parsing /etc/fstab, giving a possibility to have 2 installations on different storages on the same device

We introduced support for it in https://gitlab.com/postmarketOS/boot-deploy/-/merge_requests/18

Current state

Chrome OS and Android device already use these features, but we have a bunch of devices using u-boot scripts with hardcoded cmdline which are not going to use these features this way

Some devices use u-boot scripts for no reason, and I suggest switching these to generated extlinux.conf. For devices that require custom logic in script, the way is to apply pmos_boot= and pmos_root= in cmdline

main:

• purism-librem5 (@craftyguy)
  • uses custom logic to select dtb
  • consider implementing pmos_boot= and pmos_root= in u-boot script
  • it may be also possible to implement dtb selection with fdtdir in extlinux.conf, see boot-deploy#14 (closed)
• pine64-pinephone (@MartijnBraam, @ollieparanoid, @z3ntu, @dylanvanassche)
  • uses custom logic in uboot-user.cmd
  • consider implementing pmos_boot= and pmos_root= in u-boot script

community:

• nokia-n900
  • the only feasible way to boot is a SD card, no need for these features
  • may be possible to use generated extlinux.conf for simplicity, but not necessary

testing:

• goclever-gcta741l (@JuniorJPDJ)
  • hardcodes booting from mmcblk0
  • can it boot from USB OTG?
• google-nyan-big
  • partially solved: provides pmos_boot= and pmos_root=, but not for USB
• google-nyan-blaze
  • partially solved: the same to google-nyan-big
• google-peach-pi
  • partially solved: the same to google-nyan-big
• google-peach-pit
  • partially solved: the same to google-nyan-big
• google-snow
  • partially solved: the same to google-nyan-big
• kobo-clara
  • custom logic: execution of load_ntxkernel command
  • consider implementing it in u-boot sources or provide pmos_boot= and pmos_root=
• kobo-librah2o
  • custom logic: enter fastboot on volume key press
  • consider implementing it in u-boot sources or provide pmos_boot= and pmos_root=
• lark-freeme-70-2s (@JuniorJPDJ)
  • hardcodes booting from mmcblk0
  • can it boot from USB OTG?
• mangopi-mq-pro
  • hardcodes setenv bootdev 0
  • does it need any of discussed features?
• odroid-hc2 (@dylanvanassche)
• odroid-xu4 (@grimler)
• pine64-a64lts
• pine64-dontbeevil
• pine64-pinetab (@MartijnBraam, @dylanvanassche)
  • makes use of pmos_boot= and pmos_root= for eMMC and SD
  • can it boot from USB OTG?
• purism-librem5dev (@craftyguy)
• sipeed-licheezero
  • custom logic: uses dtbo
  • is there only one storage to boot from?
• sourceparts-pocketpc
  • provides pmos_boot= and pmos_root=
  • doesn't have any custom logic, should be able to switch to extlinux.conf, but not necessary
• tokio-techbook
  • weird script...
• tolino-shine2hd
• tolino-shine3
• xunlong-orangepi3 (@mxkrsv)
  • partially solved: provides pmos_boot= and pmos_root=, but not for USB

Implementing

Devices without custom logic

1. Remove everything related to u-boot script from device package
2. Set up deviceinfo:

• deviceinfo_dtb="something"
• deviceinfo_kernel_cmdline="something"
• deviceinfo_generate_extlinux_config="true"

3. Set depending on postmarketos-base>=25-r1 in APKBUILD
4. Merge request must depend on !3791

Devices with custom logic

For this situation we have pmos_boot= and pmos_root= parsing in initramfs

1. Make sure your device-tree uses mmc aliases. If not, number X in /dev/mmcblkX may change on each boot. See peach-pit patch for example
2. Adjust u-boot script to provide pmos_boot= and pmos_root=. See peach-pit uboot-script.cmd for example. Make sure it is implemented for all storages device can boot from