bootscripts: rk35xx: fall back to PARTUUID instead of hardcoded rootdev

[akshar27]

Description

boot-rk35xx.cmd defaults rootdev to a hardcoded /dev/mmcblk0p1 and only overrides it if armbianEnv.txt is present and sets rootdev itself. U-Boot and the kernel can number mmc controllers differently on some rk35xx boards (this board: U-Boot's mmc 0 = eMMC, but the kernel calls eMMC mmcblk1), so when armbianEnv.txt is missing or doesn't set rootdev, the hardcoded default points at the wrong (empty) device and boot drops to the initramfs shell with ALERT! /dev/mmcblk0p1 does not exist.

The script already computes PARTUUID for the boot partition a few lines above (used for the ubootpart= kernel arg), so this reuses that value: if rootdev wasn't already set by armbianEnv.txt, fall back to PARTUUID=${partuuid} instead of the hardcoded device path. PARTUUID is numbering-independent, so it works regardless of how U-Boot vs. the kernel enumerate the mmc controllers. The old hardcoded path is kept as a last-resort fallback only if the PARTUUID lookup itself comes back empty.

I intentionally left boot-generic.cmd.template alone even though it has the same setenv rootdev "/dev/mmcblk${devnum}p${distro_bootpart}" pattern (flagged in the issue as a possible instance of the same bug class) — that template is shared across many board families, and I didn't want to change shared boot behavior for boards I have no way to test, in the same PR as a board-specific fix. Happy to open a separate PR for that if maintainers agree it needs the same treatment.

Documentation summary for feature / change

Not applicable — internal boot script logic change, no user-facing config surface.

How Has This Been Tested?

• mkimage -C none -A arm -T script -d config/bootscripts/boot-rk35xx.cmd out.scr compiles cleanly (sanity check only — mkimage doesn't parse hush script semantics, it just wraps the text)
• Actual boot test on hardware

I don't have the affected hardware (LCKFB Taishan Pi RK3566) or any rk35xx board to boot-test this against. I'd appreciate it if @Tearran or another maintainer/the original reporter could confirm this boots correctly on real hardware before merge — happy to iterate on the approach if there's a reason to prefer a different fallback (e.g. the armbian.bootdev/armbian.bootdevnum token approach used in boot-seeed-rk35xx.cmd's newer fallback logic, which I considered but didn't find an initramfs consumer for, so didn't want to introduce a dependency that isn't wired up).

Fixes #10617

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings

Summary by CodeRabbit

• Bug Fixes
  • Improved boot-device detection by automatically using the computed partition identifier when available.
  • Prevented stale partition identifiers from being reused after an unsuccessful lookup.
  • Preserved the existing storage-device fallback when no partition identifier is found.

[coderabbitai]

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📝 Walkthrough

Walkthrough

The RK35xx bootscript now leaves rootdev empty initially, clears stale partuuid data, and uses the computed PARTUUID when available. It retains /dev/mmcblk0p1 as the fallback when no PARTUUID is available.

Changes

RK35xx root device selection

Layer / File(s)	Summary
Root device fallback selection config/bootscripts/boot-rk35xx.cmd	The script changes the default rootdev value to empty, clears partuuid before lookup, and selects PARTUUID=${partuuid} when available. It otherwise uses /dev/mmcblk0p1.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 9a060

RK35xx boot root-device selection now prefers the boot partition PARTUUID when no override is configured, while retaining the prior device path as a final fallback. No current merge-blocking risk is identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes address issue [#10617] by removing the default dependency on U-Boot MMC numbering, using the boot partition PARTUUID when available, and retaining the hardcoded device path only as a last-…
Out of Scope Changes check	✅ Passed	The changes are limited to the rk35xx bootscript and directly support the linked issue. No unrelated code changes are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: using PARTUUID as the fallback instead of a hardcoded root device.

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[github-actions]

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Actionable comments posted: 1

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Inline comments:
In `@config/bootscripts/boot-rk35xx.cmd`:
- Around line 46-47: Clear or initialize partuuid immediately before the
device-partition lookup so failed or non-mmc lookups cannot reuse a stale value.
Keep the existing rootdev fallback and bootargs behavior, but ensure they only
use a newly resolved partuuid.

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[akshar27]

Good catch — fixed in 9a060f4: clear partuuid immediately before the part uuid mmc ... lookup, since U-Boot leaves the variable untouched (not cleared) on a failed or skipped lookup, and a stale value from an earlier boot could otherwise get reused.

[github-actions]

✅ This PR has been reviewed and approved — all set for merge!

[EvilOlaf]

Actual boot test on hardware

is this still open?

[igorpecovnik]

I think its valid, but didn't test.