Bulk Request AVAILABLE_MODES instead of requesting each mode separately

[av-remco]

Description

Improves what the comment at line 120 of StandardModes.cc suggests

// Request one at a time. This could be improved by requesting all, but we can't use Vehicle::requestMessage for that

I noticed that QGC does not wait for COMMAND_ACKs when sending MAV_CMD_REQUEST_MESSAGE with param1 = 435, i.e. the AVAILABLE_MODES message. These are sent 25 times on startup. PX4 SITL gets flooded by the requests and fails to ack each message due to a buffer overflow, with error

pxh> ERROR [mavlink] vehicle_command_ack lost, generation 5 -> 26

This PR uses a single MAV_CMD_REQUEST_MESSAGE to get all AVAILABLE_MODES. The operation is successful when the last mode is received. It fails when the COMMAND_ACK indicates a failure.

Re-requesting missing modes is out of scope for this PR, but a good future addition. Current implementation also does not cover this.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)
• CI/Build changes
• Other

Testing

• Tested locally
• Added/updated unit tests
• Tested with simulator (SITL)
  Both PX4 1.16.1 and ArduQuad. Not relevant for Ardu, since the message is not sent. Captured the .tlog from the build and analyzed this.
• Tested with hardware

Platforms Tested

• Linux
• Windows
• macOS
• Android
• iOS

Flight Stacks Tested

• PX4
• ArduPilot

Screenshots

Custom log monitoring tool
Before:

After:

Checklist

• I have read the Contribution Guidelines
• I have read the Code of Conduct
• My code follows the project's coding standards
• I have added tests that prove my fix/feature works
• New and existing unit tests pass locally

Related Issues

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By submitting this pull request, I confirm that my contribution is made under the terms of the project's dual license (Apache 2.0 and GPL v3).

[github-actions]

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A maintainer will review this soon. Please ensure:

• CI checks pass
• Code follows coding standards
• Changes tested on relevant platforms

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[codecov]

Codecov Report

❌ Patch coverage is 39.68254% with 38 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (master@9eeee46). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/Vehicle/StandardModes.cc	38.33%	24 Missing and 13 partials ⚠️
src/Vehicle/Vehicle.cc	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #14283   +/-   ##
=========================================
  Coverage          ?   26.06%           
=========================================
  Files             ?      755           
  Lines             ?    68006           
  Branches          ?    31516           
=========================================
  Hits              ?    17727           
  Misses            ?    37502           
  Partials          ?    12777           

Flag	Coverage Δ
unittests	26.06% <39.68%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/Vehicle/Vehicle.cc	22.91% <66.66%> (ø)
src/Vehicle/StandardModes.cc	47.19% <38.33%> (ø)

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[github-actions]

Build Results

Platform Status

Platform	Status	Details
Linux	Passed	View
Windows	Passed	View
MacOS	Passed	View
Android	Passed	View

All builds passed.

Pre-commit

Check	Status	Details
pre-commit	Failed (non-blocking)	View

Pre-commit hooks: 4 passed, 36 failed, 7 skipped.

Test Results

linux-coverage: 85 passed, 0 skipped
linux-sanitizers: 85 passed, 0 skipped
Total: 170 passed, 0 skipped

Code Coverage

Coverage: 59.1%

No baseline available for comparison

Artifact Sizes

Artifact	Size
QGroundControl	247.81 MB
QGroundControl-aarch64	177.23 MB
QGroundControl-installer-AMD64	134.83 MB
QGroundControl-installer-AMD64-ARM64	77.46 MB
QGroundControl-installer-ARM64	106.16 MB
QGroundControl-linux	338.35 MB
QGroundControl-mac	188.82 MB
QGroundControl-windows	188.84 MB
QGroundControl-x86_64	172.36 MB
No baseline available for comparison

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_{Updated: 2026-04-17 07:44:54 UTC • Triggered by: Android}