kernel-dtb: fatal if BOOT_FDT_FILE is unset (fixes #8083)

[iav]

Summary

• Fixes [Bug]: kernel-dtb does not output when unset BOOT_FDT_FILE is present #8083: kernel-dtb silently produced an empty package when BOOT_FDT_FILE was unset (typical case: board config relies on a post_family_config_branch_* hook that unsets it for some kernel branches — e.g. orangepi5-max on edge).
• kernel_dtb_only_build() now fails fast with a diagnostic pointing at both likely sources (board config, post-family hook).
• Regular kernel artifact is unaffected — it does not go through kernel_dtb_only_build().

Test plan

• ./compile.sh kernel-dtb BOARD=orangepi5-max BRANCH=edge — fatal, rc=43, message references post_family_config_* hook (this board unsets BOOT_FDT_FILE in an edge-specific hook).
• ./compile.sh kernel-dtb BOARD=orangepi5-max BRANCH=current — non-fatal path, .deb produced with preprocessed DTS (stays set on current).
• bash -n lib/functions/compilation/kernel.sh — OK.
• shellcheck --severity=error lib/functions/compilation/kernel.sh — OK.

Summary by CodeRabbit

• Bug Fixes
  • Elevated the message for missing kernel device-tree configuration to an error with clearer guidance, making the issue more visible during builds.
  • Prevents silent skipping of device-tree processing when configuration is unset, ensuring misconfigurations are surfaced early and easier to resolve.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Reviewing files that changed from the base of the PR and between be4dab5 and be4858d.

📒 Files selected for processing (1)

• lib/functions/compilation/kernel.sh

🚧 Files skipped from review as they are similar to previous changes (1)

• lib/functions/compilation/kernel.sh

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📝 Walkthrough

Walkthrough

kernel_dtb_only_build now emits an error-level diagnostic (expanded explanatory text including package and preprocessing note) when BOOT_FDT_FILE is unset, but still returns success (return 0); .dts convenience processing remains gated on BOOT_FDT_FILE being set.

Changes

Cohort / File(s)	Summary
Kernel DTB build logic lib/functions/compilation/kernel.sh	Changed handling for unset BOOT_FDT_FILE: replaced a prior warning message with an error-level/expanded diagnostic about producing linux-dtb while skipping preprocessed DTS copy, but retained return 0. .dts convenience processing still only runs when BOOT_FDT_FILE is set.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 I nudged the build at break of day,

Found BOOT_FDT_FILE had gone astray.
I shouted loud (but left the flow),
A gentle error — on we go.
Hops and patches, all okay!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately reflects the main change: converting a warning into a fatal error when BOOT_FDT_FILE is unset, and references the specific issue being fixed.
Linked Issues check	✅ Passed	The PR successfully addresses all objectives from #8083: detects BOOT_FDT_FILE unset condition, emits diagnostic alert, preserves .deb creation, and enables users to identify and fix board config/hook issues.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing #8083; only kernel_dtb_only_build control-flow is modified with no alterations to exported entities or other functions.

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🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

lib/functions/compilation/kernel.sh (1)

175-190: ⚠️ Potential issue | 🟡 Minor

Move the BOOT_FDT_FILE guard before the DTB build.

Line 180 still runs kernel_build before the new fatal validation, so an unset BOOT_FDT_FILE can spend time building/installing DTBs—or fail earlier for an unrelated build reason—before showing the intended diagnostic. Moving the guard to the top makes this path truly fail-fast.

Suggested change

 function kernel_dtb_only_build() {
 	display_alert "Kernel DTB-only for development" "KERNEL_DTB_ONLY: ${KERNEL_DTB_ONLY}" "info"
+
+	# kernel-dtb needs BOOT_FDT_FILE to know which .dtb to preprocess into a .dts.
+	# If it is unset (board config, or a post_family_config_* hook that unset it),
+	# we cannot continue — bail out loudly instead of silently producing an empty package.
+	if [[ -z "${BOOT_FDT_FILE}" ]]; then
+		exit_with_error "Board '${BOARD}' branch '${BRANCH}' has no BOOT_FDT_FILE set; kernel-dtb cannot produce a preprocessed DTS. Check the board config and any post_family_config_* hook that may unset it."
+	fi
+
 	# Do it in two separate steps, first build the dtbs then install them.
 	build_targets_build=("dtbs")
 	build_targets_install=("dtbs_install")
 	LOG_SECTION="kernel_build" do_with_logging do_with_hooks kernel_build
 
 	display_alert "Kernel DTB-only .deb, for development/convenience" "kernel dtb build done" "info"
 
 	display_alert "Considering further .dts convenience processing" "for board '${BOARD}' branch '${BRANCH}'" "info"
-
-	# kernel-dtb needs BOOT_FDT_FILE to know which .dtb to preprocess into a .dts.
-	# If it is unset (board config, or a post_family_config_* hook that unset it),
-	# we cannot continue — bail out loudly instead of silently producing an empty package.
-	if [[ -z "${BOOT_FDT_FILE}" ]]; then
-		exit_with_error "Board '${BOARD}' branch '${BRANCH}' has no BOOT_FDT_FILE set; kernel-dtb cannot produce a preprocessed DTS. Check the board config and any post_family_config_* hook that may unset it."
-	fi
 
 	display_alert "Kernel DTB-only for development" "Copying preprocessed versions of ${BOOT_FDT_FILE}" "info"

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@lib/functions/compilation/kernel.sh` around lines 175 - 190, The
BOOT_FDT_FILE existence check should run before any build starts to fail-fast;
inside kernel_dtb_only_build, move the current BOOT_FDT_FILE guard so it
executes before setting build_targets_build/build_targets_install and before
invoking kernel_build (LOG_SECTION and do_with_logging/do_with_hooks). Ensure
the guard still logs the same clear fatal message and uses exit_with_error when
BOOT_FDT_FILE is empty, preventing unnecessary dtb build/install work by
kernel_build.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Outside diff comments:
In `@lib/functions/compilation/kernel.sh`:
- Around line 175-190: The BOOT_FDT_FILE existence check should run before any
build starts to fail-fast; inside kernel_dtb_only_build, move the current
BOOT_FDT_FILE guard so it executes before setting
build_targets_build/build_targets_install and before invoking kernel_build
(LOG_SECTION and do_with_logging/do_with_hooks). Ensure the guard still logs the
same clear fatal message and uses exit_with_error when BOOT_FDT_FILE is empty,
preventing unnecessary dtb build/install work by kernel_build.

---

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📥 Commits

Reviewing files that changed from the base of the PR and between 3814034 and 9eb62bc.

📒 Files selected for processing (1)

• lib/functions/compilation/kernel.sh

[iav]

Moved the guard to the top of kernel_dtb_only_build() — before kernel_build — so we fail fast without wasting time on the dtbs target. Dropped the inline comment since the exit_with_error message already spells out the cause and the places to check.

[rpardini]

I'm probably missing something, but I guess kernel-dtb can produce a linux-dtb package no matter if it knows the exact DTB for the board or not. The "extra stuff" (preprocessed, etc) done for a board does depend on the FDT being set, but I guess it's a separate concern?

[iav]

You're right — linux-dtb package comes from make dtbs + dtbs_install and doesn't need BOOT_FDT_FILE at all; only the convenience preprocessed-DTS copy in output/ does. My fatal breaks the package build, which is a regression.

The original complaint in #8083 was about silent behaviour: a warn-level message is easy to miss, and the reporter saw an empty output/ with no obvious reason. I'll switch to: keep kernel-dtb producing the .deb as before, but emit an err-level alert (package OK, preprocessed DTS skipped, with a hint about the board config / post_family_config_* hook) before return 0.