feat(params): add board-level read-only parameter support by julianoes · Pull Request #26522 · PX4/PX4-Autopilot

julianoes · 2026-02-18T22:44:18Z

Integrators can declare read-only parameters in a per-board YAML file: readonly_params.yaml.

There are two ways to define the read-only params:

"block": default writable, explicitly list params to be locked
"allow": default readonly, explicitly list params to be writable

Enforcement is activated by param lock in rcS after all startup scripts have run, so board defaults and airframe scripts can still set params during init.

The feedback via MAVLink uses the new
MAV_PARAM_ERROR_READ_ONLY as part of the PARAM_ERROR message.

This also includes an extension to param show:

nsh> param show -l
Symbols: x = used, + = saved, * = unsaved, l = locked
x + l BAT1_N_CELLS [6,37] : 2

Closes #12429.
Closes #14493.

github-actions · 2026-02-18T22:52:31Z

No broken links found in changed files.

github-actions · 2026-02-18T22:53:43Z

🔎 FLASH Analysis

px4_fmu-v5x [Total VM Diff: 416 byte (0.02 %)]

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px4_fmu-v6x [Total VM Diff: 416 byte (0.02 %)]

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Updated: 2026-04-08T18:51:26

hamishwillee

Docs are great, but we really need the read-only field to be injected into parameter metadata so that a GCS doesn't have to try to read it, and doesn't offer the option. Once it is in the metadata I can also read it.

You'd have to update src/lib/parameters/px_generate_params.py‎ to add a new property like the following to generated parameters.

 * @read-only True

We can then update the src parser and markdown out exc to generate appropriate XML and markdown.

julianoes · 2026-02-19T02:18:57Z

Ah yes, we can add that.

hamishwillee · 2026-02-19T03:16:38Z

Ah yes, we can add that.

If you can add to the generated params stuff I can fix up the markdown output.

dakejahl

Amazing!

julianoes · 2026-02-19T17:59:43Z

@hamishwillee is this ok?

QGC PR: mavlink/qgroundcontrol#14007

If you can add to the generated params stuff I can fix up the markdown output.

What do you mean exactly?

hamishwillee · 2026-02-19T22:04:25Z

@hamishwillee is this ok?

To my mind the QGC change would be that the read only parameters

would be shown with some visual difference in lists - i.e. different than ones that can be edited and ones that have been edited (shown in red). Usually you'd do something like this with a little icon - you can't use grey because that means disabled.
In popup would have something very clear to indicate that they are read only. Again, I'd tend to use a lock icon or similar.

I can't see what you have done in the background list, and to me an icon or colour change would be much more visually obvious than this text.

So yes, this is OK, but would prefer optimal.

What do you mean exactly?

I mean for the parameter metadata rendering in docs the readonly information needs to be captured in the parameter source parser. You must have done this though or you wouldn't be able to generate parameters.xml.

So what I am saying is that once this merges, I can take on the update to generate the updates to the documentation. Unless you want to do that.

ryanjAA · 2026-02-19T22:18:08Z

This is so good!

julianoes · 2026-02-20T00:55:46Z

would be shown with some visual difference in lists

Yeah, I can try that.

I mean for the parameter metadata rendering in docs the readonly information needs to be captured in the parameter source parser.

I think it's just ignored. There are no locked parameters for the upstream version, so this really only applies to integrator forks that would use it.

julianoes · 2026-02-20T01:37:46Z

@hamishwillee something like this?

hamishwillee · 2026-02-20T07:22:33Z

@julianoes Yes - that's what I was thinking. Lovely.

mrpollo · 2026-02-22T01:22:36Z

Whats missing here? it would be nice to get this merged, cool feature

julianoes · 2026-02-22T04:15:17Z

The one thing I should check is how/if this conflicts with ArduPilot, mostly concerning the QGC side. I wasn't aware of the fact that they already have it, or something like it.

dakejahl · 2026-04-02T23:16:28Z

Did we get the QGC side figured out? I think this is a great feature and would love to get it in.

julianoes · 2026-04-08T18:39:02Z

Looking into what is going on now.

Integrators can declare read-only parameters in a per-board YAML file: readonly_params.yaml. There are two ways to define the read-only params: - "block": default writable, explicitly list params to be locked - "allow": default readonly, explicitly list params to be writable Enforcement is activated by `param lock` in rcS after all startup scripts have run, so board defaults and airframe scripts can still set params during init. The feedback via MAVLink uses the new MAV_PARAM_ERROR_READ_ONLY as part of the PARAM_ERROR message.

github-actions · 2026-04-14T22:25:11Z

🔎 FLASH Analysis

px4_fmu-v5x [Total VM Diff: 416 byte (0.02 %)]

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Updated: 2026-04-14T22:24:55

github-actions · 2026-04-14T22:38:50Z

No broken links found in changed files.

hamishwillee

Approving for the docs part. The mavlink bits look good too, but I haven't tested.

julianoes requested review from MaEtUgR and hamishwillee February 18, 2026 22:44

github-actions bot added the Documentation 📑 label Feb 18, 2026

hamishwillee reviewed Feb 18, 2026

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dakejahl previously approved these changes Feb 19, 2026

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julianoes dismissed dakejahl’s stale review via ff4699c February 19, 2026 17:51

julianoes force-pushed the pr-readonly-params branch from 9dd8094 to ff4699c Compare February 19, 2026 17:51

julianoes mentioned this pull request Feb 19, 2026

Add support for read-only parameters mavlink/qgroundcontrol#14007

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julianoes force-pushed the pr-readonly-params branch from ff4699c to 50d2442 Compare April 8, 2026 18:43

julianoes changed the title ~~params: add board-level read-only parameter support~~ feat(params): add board-level read-only parameter support Apr 8, 2026

julianoes force-pushed the pr-readonly-params branch from 50d2442 to ccb86d1 Compare April 14, 2026 22:18

hamishwillee approved these changes Apr 14, 2026

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