VTX: Fetch power level count and min from FC (resolves #2202 conflict)

[sensei-hacker]

User description

Summary

This PR resolves the merge conflict in #2202 by adding support for dynamic power_min from the flight controller while maintaining compatibility with INAV 9.0 RCx.

Original PR: #2202 by @bkleiner
Conflict cause: PR #2206 added MSP VTX support which uses 0-based power indexing (index 0 = power off), while #2202 assumed all devices are 1-based.

Changes

1. Added power_min Field

• Added FC.VTX_CONFIG.power_min field (default: 1)
• Allows dynamic minimum power index from firmware

2. Enhanced MSP Parser (js/msp/MSPHelper.js)

• Added defensive buffer length checking for backward compatibility
• Reads power_min from firmware if available (INAV 9.1+)
• Falls back to device-type logic for firmware 9.0:
  • MSP VTX: min = 0 (supports power off at index 0)
  • SmartAudio/Tramp: min = 1 (power off not supported)
• Fixed typo: "wether" → "whether"

3. Resolved Merge Conflict (js/vtx.js)

• Removed both POWER_MIN constant and getMinPower()/getMaxPower() functions
• Kept DEV_MSP = 6 constant from master
• Eliminates all hardcoded device-type power logic

4. Updated VTX Power UI (tabs/configuration.js)

• Changed from VTX.POWER_MIN to FC.VTX_CONFIG.power_min
• Now uses dynamic values from firmware

Compatibility

✅ Configurator 9.1 (this PR) + Firmware 9.0

Firmware sends 11 bytes, configurator detects missing power_min and falls back to device-type logic

• MSP VTX correctly shows power indices 0-4
• SmartAudio/Tramp correctly show power indices 1-N

✅ Configurator 9.0 (current) + Firmware 9.1 (future)

Old configurator ignores extra bytes, uses hardcoded logic

• No breaking changes created

Firmware Enhancement (Future)

The configurator is ready to receive power_min from firmware. To complete this feature, add one byte to MSP_VTX_CONFIG response in firmware:

// In src/main/fc/fc_msp.c, case MSP_VTX_CONFIG:
sbufWriteU8(dst, vtxDevice->capability.powerCount);

// NEW: Add minimum valid power index
uint8_t minPowerIndex = 0;
if (deviceType == VTXDEV_SMARTAUDIO || deviceType == VTXDEV_TRAMP) {
    minPowerIndex = 1;
}
sbufWriteU8(dst, minPowerIndex);  // Byte 12

Once firmware sends this byte, the configurator will automatically use it instead of the fallback logic.

Benefits

✅ Preserves PR #2202's original intent - eliminates hardcoded device-type logic
✅ Single source of truth - firmware owns all VTX capabilities
✅ Fixes MSP VTX power off support (index 0 now accessible)
✅ Backward compatible with firmware 9.0
✅ Forward compatible - ready for firmware 9.1 enhancement
✅ No breaking changes in either upgrade direction

Testing

• ✅ JavaScript syntax validation passed
• ✅ Merge conflict fully resolved
• ✅ Defensive buffer parsing prevents crashes with older firmware
• 🔲 Hardware testing needed (MSP, SmartAudio, Tramp VTX devices)

Related

• Supersedes: vtx: fetch powerlevel count from fc #2202 (original PR with merge conflict)
• Conflicts with: Allow a power index range of 0-4 for MSP VTX devices #2206 (MSP VTX support - already merged)
• Requires: msp: expose number of vtx power levels, bands and channels inav#10395 (firmware support - already in 9.0)

Checklist

• Code follows project style guidelines
• Self-review completed
• Changes generate no new warnings
• Added defensive buffer checking for backward compatibility
• Tested syntax validation
• Hardware testing (requires devices)

Description

• Add dynamic VTX power configuration from firmware with backward compatibility

  • New fields: band_count, channel_count, power_count, power_min in FC.VTX_CONFIG
  • Reads power_min from firmware (INAV 9.1+) with fallback logic for 9.0

• Enhanced MSP parser with defensive buffer checking

  • Validates buffer length before reading VTX table data
  • Falls back to device-type logic (MSP VTX: min=0, others: min=1) if firmware doesn't send power_min
  • Fixed typo: "wether" → "whether"

• Removed hardcoded power level functions from VTX module

  • Deleted getMinPower() and getMaxPower() functions
  • Eliminates device-type specific power logic from configurator

• Updated VTX power UI to use firmware values

  • Changed from VTX.getMinPower/getMaxPower() to FC.VTX_CONFIG.power_min and power_count

---

Diagram Walkthrough

flowchart LR
  FW["Firmware 9.0/9.1<br/>MSP_VTX_CONFIG"] -->|sends power_min| MSPHelper["MSPHelper.js<br/>Parse with buffer check"]
  MSPHelper -->|fallback device logic| FC["FC.VTX_CONFIG<br/>power_min, power_count"]
  FC -->|dynamic values| ConfigUI["Configuration UI<br/>Power dropdown"]
  VTX["VTX.js<br/>Remove hardcoded logic"] -.->|eliminated| ConfigUI

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File Walkthrough

	Relevant files
Enhancement	fc.js Add VTX configuration fields for power levels                        js/fc.js Added four new fields to FC.VTX_CONFIG: band_count, channel_count, power_count, power_min Set default value of power_min to 1 for backward compatibility +4/-0      MSPHelper.js Enhance MSP parser with dynamic power configuration            js/msp/MSPHelper.js Added defensive buffer length checking before reading VTX table data Reads band_count, channel_count, power_count from firmware if available Implements fallback logic for power_min: MSP VTX uses 0, others use 1 if firmware doesn't send it Fixed typo: "wether" → "whether" +20/-1    configuration.js Update VTX power UI to use firmware values                              tabs/configuration.js Changed power dropdown generation to use FC.VTX_CONFIG.power_min instead of VTX.getMinPower() Changed power dropdown upper bound to use FC.VTX_CONFIG.power_count instead of VTX.getMaxPower() Now uses dynamic firmware values instead of hardcoded device-type logic +1/-3
Bug fix	vtx.js Remove hardcoded VTX power level functions                              js/vtx.js Removed getMinPower() function that returned device-type specific minimum power index Removed getMaxPower() function that returned device-type specific maximum power index Eliminates hardcoded device-type power logic from configurator +0/-17

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[qodo-code-review]

PR Compliance Guide 🔍

All compliance sections have been disabled in the configurations.

[sensei-hacker]

Implemented suggestion #1 for robustness. Suggestion #2 is incorrect: powerCount should be the maximum valid index, not count. Current loop correctly includes all indices.

[sensei-hacker]

Requires iNavFlight/inav#11190 to be fully effective (otherwise the fallback is used)