feat(oot): support external MAVLink handler, stream, and dialect with opt in custom init scripts in Out of Tree modules by methodmissing · Pull Request #27415 · PX4/PX4-Autopilot

methodmissing · 2026-05-20T13:48:35Z

mavlink: external handler, stream, and dialect support for out-of-tree modules

Summary

References #26261 , specifically to attempt to address some difficulties I bumped into with a "clean cut" out of tree external module

Adds first-class MAVLink support for out-of-tree (OOT) modules: custom dialect
code generation, inbound message handling, outbound streaming, and ROMFS init
script injection — all without patching PX4 source.

Currently, OOT modules that need custom MAVLink messages must manually symlink
dialect XMLs, patch mavlink_receiver.cpp, and hand-edit rcS. This PR
eliminates all of that with a convention-based approach.

Tested end-to-end with a PX4 module and driver for the SE05x secure element present on Pixhawk 6X boards that uses 6 custom MAVLink messages for PKI enrollment over USB, running on Pixhawk 6X-RT hardware.

Changes

1. External MAVLink handler registry (`mavlink_ext_handler.{h,cpp}`)

Static callback table (max 8 entries, probably should be configurable) for inbound custom messages. Registration
is mutex-protected; dispatch is lock-free from the receiver thread's default
case:

MavlinkReceiver::handle_message()
  └─ switch(msg->msgid)
       ├─ case HEARTBEAT: ...
       ├─ case ...: (built-in handlers)
       └─ default:
            mavlink_ext_handler_dispatch(msg)  ← NEW
              └─ iterates registered callbacks

It should have no overhead in the hot / happy path as it injects at the default case handler which currently hard drops any unknown MAVLink message IDs.

OOT module usage:

#include <modules/mavlink/mavlink_ext_handler.h>

// In module init:
mavlink_ext_handler_register(MAVLINK_MSG_ID_SE05X_PROVISION,
                             handle_provision, this);

// In module stop:
mavlink_ext_handler_unregister(MAVLINK_MSG_ID_SE05X_PROVISION);

2. External MAVLink stream registry (`mavlink_ext_stream.{h,cpp}`)

Static callback table for outbound streams, dispatched from Mavlink::task_main()
after the built-in stream loop. Supports rate-limited intervals and integrates
with SET_MESSAGE_INTERVAL so QGC/pymavlink can control OOT stream rates
identically to built-in streams:

#include <modules/mavlink/mavlink_ext_stream.h>

mavlink_ext_stream_register(
    MAVLINK_MSG_ID_SE05X_CSR, "SE05X_CSR",
    emit_csr_fragment, this,
    100000);  // 10 Hz

// SET_MESSAGE_INTERVAL fallback in mavlink_receiver.cpp:
mavlink_ext_stream_set_interval(msg_id, interval_us);

3. CMake dialect registration (`px4_add_external_mavlink_dialect`)

Shared CMake function that copies OOT dialect XMLs into mavgen's search path
and auto-overrides CONFIG_MAVLINK_DIALECT from common:

# In OOT module's CMakeLists.txt:
px4_add_external_mavlink_dialect(
    XML ${CMAKE_CURRENT_SOURCE_DIR}/../../mavlink/standard.xml
)

The dialect XML uses standard <include>common.xml</include> inheritance, so
all built-in messages remain available. Multiple dialects from different OOT
modules are supported.

4. ROMFS init script injection (`ROMFS/CMakeLists.txt`, `rcS`)

OOT modules can provide init/rc.ext_modules which is automatically copied
into the ROMFS image and sourced by rcS after the logger starts:

rcS boot sequence:
  ...
  rc.logging           ← logger starts first
  rc.ext_modules       ← OOT module init (if file exists)
  rc.vtxtable
  ...
  mavlink boot_complete

Example init/rc.ext_modules:

se05x start
se05x_mavlink start
se05x derive-keys &

Directory convention:

my_external_module/
├── init/
│   └── rc.ext_modules       ← auto-injected into ROMFS, optional
├── mavlink/
│   └── my_dialect.xml       ← custom MAVLink messages, optional
├── msg/
│   └── MyTopic.msg          ← custom uORB topics, already supported upstream
└── src/
    ├── CMakeLists.txt
    └── modules/
        └── my_module/

Note on msg/: OOT uORB message definitions currently must live in the
OOT module's msg/ directory and are registered via px4_add_module() with
the MSG_SRCS parameter. PX4's msg/ directory is reserved for in-tree
topics. See Out-of-Tree Modules.

Integration points (minimal PX4 source changes)

File	Change	Lines
`mavlink_receiver.cpp`	`#include` + `dispatch()` in `default:` + `set_interval` fallback	+17
`mavlink_main.cpp`	`#include` + `ext_stream_dispatch()` in main loop	+4
`CMakeLists.txt`	`include()` dialect cmake + dialect auto-override after `add_subdirectory`	+21
`ROMFS/CMakeLists.txt`	Copy `rc.ext_modules` into ROMFS image	+25
`rcS`	Source `rc.ext_modules` after `rc.logging`	+11

All new files: mavlink_ext_handler.{h,cpp}, mavlink_ext_stream.{h,cpp},
px4_add_external_mavlink_dialect.cmake.

Design decisions

Static arrays, not dynamic allocation. Both registries use fixed-size
arrays (8 slots each, can be configurable). No heap allocation at runtime. Lock-free dispatch.
Mutex on registration only. register/unregister are mutex-protected
(called once at init/shutdown). dispatch iterates the array without locking
— safe because entries are only appended/cleared while the slot count is
atomically visible.
Dialect override is opt-in. Only overrides CONFIG_MAVLINK_DIALECT if
it's the default common. If a board already sets a specific dialect, it's
preserved.
Init script is optional. The rc.ext_modules hook is if [ -f ... ]
guarded. No impact on builds without EXTERNAL_MODULES_LOCATION.

Testing

Validated on Pixhawk 6X-RT (fmu-v6xrt) with the SE05x secure element OOT
module performing:

Full PKI enrollment pipeline (6 custom MAVLink messages, fragmented
certificate transfers)
Bidirectional ECIES crypto verification (ECDH + HKDF + AES-256-CBC +
HMAC-SHA384)
ECDSA-P384 signature verification
Session key derivation with HMAC proof
ROMFS init auto-start

Example usage in OOT module

Header file of the MAVLink handler concerns

/**
 * @file se05x_mavlink.h
 * @brief SE05x MAVLink bridge (uORB ↔ SE05x driver for PKI enrollment)
 */

#pragma once

#define MODULE_NAME "se05x_mavlink"

#include <px4_platform_common/px4_config.h>
#include <px4_platform_common/module.h>
#include <px4_platform_common/module_params.h>
#include <px4_platform_common/posix.h>
#include <px4_platform_common/time.h>
#include <px4_platform_common/px4_work_queue/ScheduledWorkItem.hpp>
#include <pthread.h>

#include <uORB/Subscription.hpp>
#include <uORB/Publication.hpp>
#include <uORB/topics/se05x_certificate_enrollment_response.h>
#include <uORB/topics/se05x_certificate_signing_request.h>
#include <uORB/topics/se05x_provision.h>
#include <uORB/topics/se05x_ecies_test_request.h>
#include <uORB/topics/se05x_ecies_test_response.h>
#include <uORB/topics/se05x_command.h>
#include <uORB/topics/se05x_response.h>

/**
 * @brief SE05x MAVLink bridge module
 *
 * Processes uORB-based PKI requests and delegates to the SE05x driver library.
 */
class SE05xMavlink : public ModuleBase, public ModuleParams, public px4::ScheduledWorkItem
{
public:
    SE05xMavlink();
    ~SE05xMavlink() override;

    static Descriptor desc;

    /** @see ModuleBase */
    static int task_spawn(int argc, char *argv[]);

    /** @see ModuleBase */
    static int custom_command(int argc, char *argv[]);

    /** @see ModuleBase */
    static int print_usage(const char *reason = nullptr);

    /** @see ScheduledWorkItem::Run() */
    void Run() override;

    /** Print driver status */
    int print_status() override;

    /**
     * @brief Sign data with ECDSA-P384 (CNSA Suite 2.0) via the SE05x
     *
     * Hashes the input with SHA-384, then signs the hash using the SE05x
     * signing key. Returns the signature in ASN.1 DER format.
     *
     * @param command_data Data to sign
     * @param command_len Length of data
     * @param signature Output buffer for signature (ASN.1 DER, typically 104-106 bytes)
     * @param signature_len Input: buffer size, Output: actual signature length
     * @return 0 on success, negative on error
     */
    int sign_command(const uint8_t *command_data, size_t command_len,
                     uint8_t *signature, size_t *signature_len);

    // emit_csr_stream is a static free function used as a mavlink ext_stream callback.
    friend bool emit_csr_stream(uint8_t channel, void *user_data);

    // emit_enc_csr_stream streams the encryption CSR (key_purpose=1) after the signing CSR.
    friend bool emit_enc_csr_stream(uint8_t channel, void *user_data);

    // emit_ecies_response is a static free function used as a mavlink ext_stream callback.
    friend bool emit_ecies_response(uint8_t channel, void *user_data);

    /**
     * @brief Store an enrollment fragment directly (called from MAVLink handler)
     *
     * Bypasses uORB to avoid single-slot publication races when the host
     * sends multiple fragments faster than the 100ms Run() cycle.
     */
    void handle_enrollment_fragment(uint16_t total, uint16_t offset,
                                    const uint8_t *data, uint8_t data_len);

    /**
     * @brief Store an encryption enrollment fragment (called from MAVLink handler)
     */
    void handle_enc_enrollment_fragment(uint16_t total, uint16_t offset,
                                        const uint8_t *data, uint8_t data_len);

    /**
     * @brief Store the provisioner encryption public key (called from MAVLink handler)
     */
    void store_provisioner_key(const uint8_t *key, size_t len);

private:
    /**
     * @brief Initialize the module and schedule work
     */
    int init();

    /**
     * @brief Process incoming uORB requests and call library functions
     */
    void process_uorb_requests();

    /**
     * @brief Check for responses from the SE05x service thread
     */
    void process_service_responses();

    /**
     * @brief Provisioning state machine (driven by service thread responses)
     */
    enum class ProvState : uint8_t {
        Idle = 0,
        WaitProvision,       // Waiting for OP_PROVISION response
        WaitSigningCSR,      // Waiting for OP_GENERATE_CSR(signing) response
        WaitEnrollment,      // Waiting for OP_ENROLLMENT response
        WaitEncCSR,          // Waiting for OP_GENERATE_CSR(encryption) response
        WaitEncEnrollment,   // Waiting for OP_ENC_ENROLLMENT response
        WaitEciesTest,       // Waiting for OP_ECIES_TEST response
    };

    ProvState _prov_state{ProvState::Idle};

    /** Publish a command to the SE05x service thread */
    void publish_command(uint8_t op, const uint8_t *payload = nullptr, uint16_t payload_len = 0);

    // uORB subscriptions for inbound PKI material (offboard → vehicle)
    uORB::Subscription _provision_sub{ORB_ID(se05x_provision)};

    // uORB subscription for ECIES test requests
    uORB::Subscription _ecies_test_request_sub{ORB_ID(se05x_ecies_test_request)};

    // uORB command/response for SE05x service thread
    orb_advert_t _cmd_pub{nullptr};
    uORB::Subscription _resp_sub{ORB_ID(se05x_response)};

    // Fragment reassembly buffer for CA certificate (from multiple uORB messages)
    static constexpr size_t CA_CERT_MAX = 480;  // P-384 DER certs ~441 bytes
    uint8_t  _ca_cert_buf[CA_CERT_MAX]{};
    uint16_t _ca_cert_total_len{0};
    uint16_t _ca_cert_received{0};
    uint8_t  _ca_cert_target_system{0};
    uint8_t  _ca_cert_target_component{0};
    uint8_t  _ca_cert_force_regenerate{0};

    // Provisioner encryption public key (from SE05X_PROVISIONER_KEY, stored before provisioning)
    uint8_t  _provisioner_key[97]{};
    bool     _provisioner_key_received{false};

    // Device identity for CSR generation (populated from board info during provisioning)
    char     _csr_serial[40]{};
    char     _csr_model[16]{};

    // CSR output buffer (populated from service response, fragmented by emit_csr_stream)
    static constexpr size_t CSR_MAX = 512;
    static constexpr size_t CSR_FRAG_MAX = 190;  // csr_data[190] per MAVLink frame
    uint8_t  _csr_buf[CSR_MAX]{};
    uint16_t _csr_total_len{0};
    uint16_t _csr_send_offset{0};
    bool     _csr_ready{false};

    // Fragment reassembly buffer for device certificate enrollment
    // Populated directly by handle_mavlink_enrollment (not via uORB)
    static constexpr size_t DEV_CERT_MAX = 480;
    uint8_t  _dev_cert_buf[DEV_CERT_MAX]{};
    uint16_t _dev_cert_total_len{0};
    uint16_t _dev_cert_received{0};
    bool     _enrollment_ready{false};

    // Encryption CSR output buffer (populated from service response after signing CSR)
    uint8_t  _enc_csr_buf[CSR_MAX]{};
    uint16_t _enc_csr_total_len{0};
    uint16_t _enc_csr_send_offset{0};
    bool     _enc_csr_ready{false};

    // Encryption certificate enrollment (key_purpose=1)
    uint8_t  _enc_cert_buf[DEV_CERT_MAX]{};
    uint16_t _enc_cert_total_len{0};
    uint16_t _enc_cert_received{0};
    bool     _enc_enrollment_ready{false};

    // ECIES test state (populated by handle_mavlink_ecies_test, consumed by service thread)
    uint8_t  _ecies_phase{0};  // 0=ECIES encrypt, 1=ECDSA sign, 2=session key derivation
    uint8_t  _ecies_host_pubkey[97]{};
    uint8_t  _ecies_plaintext[32]{};
    uint8_t  _ecies_target_system{0};
    uint8_t  _ecies_target_component{0};

    // ECIES test response (populated from service response, sent by emit_ecies_response)
    int8_t   _ecies_resp_result{0};
    uint8_t  _ecies_resp_phase{0};
    uint8_t  _ecies_resp_ephem_pubkey[97]{};
    uint8_t  _ecies_resp_iv[12]{};
    uint8_t  _ecies_resp_ciphertext[32]{};
    uint8_t  _ecies_resp_hmac_tag[48]{};
    uint8_t  _ecies_response_sends{0};  // >0 = send on next N dispatch cycles (covers all channels)

    static constexpr uint32_t SCHEDULE_INTERVAL_US = 100000; // 100ms
};

Custom MAVLink SE05x dialect

Includes common.xml

<?xml version="1.0"?>
<mavlink>
    <include>common.xml</include>
    <version>3</version>
    <dialect>1</dialect>
    <!--
        SE05x Secure Element Custom MAVLink Messages

        These messages provide secure provisioning capabilities for the NXP SE05x
        secure element (CNSA Suite 2.0 / FIPS 140-3).

        Message IDs: 55000-55005 (custom range, outside common/standard allocation)

        P-384 certificates exceed a single MAVLink frame (253-byte payload limit).
        All certificate/CSR fields support fragment-based delivery via offset and
        total_len fields.  The receiver reassembles fragments by offset before
        triggering provisioning.
    -->
    <messages>
        <!-- SE05X_PROVISION: Trigger CSR/keypair generation on-vehicle -->
        <message id="55000" name="SE05X_PROVISION">
            <description>Trigger SE05x provisioning: generate (or reuse) keypair and publish CSR+attestation for server-side signing. CA certificate may span multiple fragments.</description>
            <field type="uint8_t" name="target_system">Target system ID (0 = broadcast)</field>
            <field type="uint8_t" name="target_component">Target component ID (0 = broadcast)</field>
            <field type="uint8_t" name="force_regenerate">0 = reuse existing if present, 1 = regenerate keypair</field>
            <field type="uint16_t" name="ca_certificate_total_len">Total CA certificate length in bytes (across all fragments)</field>
            <field type="uint16_t" name="ca_certificate_offset">Byte offset of this fragment within the full certificate</field>
            <field type="uint8_t" name="ca_certificate_len">Length of certificate data in this fragment (0-244)</field>
            <field type="uint8_t[244]" name="ca_certificate">CA certificate fragment (DER, max 244 bytes per frame)</field>
        </message>

        <!-- SE05X_CERTIFICATE_SIGNING_REQUEST: Device CSR response (outbound) -->
        <message id="55001" name="SE05X_CERTIFICATE_SIGNING_REQUEST">
            <description>Device certificate signing request for PKI enrollment. CSR data may span multiple fragments. Device identity fields are populated in every fragment.</description>
            <field type="uint8_t" name="target_system">Target system ID (0 = broadcast)</field>
            <field type="uint8_t" name="target_component">Target component ID (0 = broadcast)</field>
            <field type="uint16_t" name="csr_data_total_len">Total CSR length in bytes (across all fragments)</field>
            <field type="uint16_t" name="csr_data_offset">Byte offset of this fragment</field>
            <field type="uint8_t" name="csr_data_len">Length of CSR data in this fragment (0-190)</field>
            <field type="uint8_t[190]" name="csr_data">CSR fragment in DER format (PKCS#10, max 190 bytes per frame)</field>
            <field type="uint8_t[40]" name="device_serial">PX4 GUID hex string (null-terminated)</field>
            <field type="uint8_t[16]" name="device_model">Device model identifier (null-terminated)</field>
            <field type="uint8_t" name="key_purpose">0 = signing (digitalSignature), 1 = encryption (keyAgreement)</field>
        </message>

        <!-- SE05X_CERTIFICATE_ENROLLMENT_RESPONSE: CA-signed device certificate (inbound) -->
        <message id="55002" name="SE05X_CERTIFICATE_ENROLLMENT_RESPONSE">
            <description>CA-signed device certificate for enrollment into the SE05x secure element. Certificate may span multiple fragments.</description>
            <field type="uint8_t" name="target_system">Target system ID</field>
            <field type="uint8_t" name="target_component">Target component ID</field>
            <field type="int8_t" name="result">Result code (0 = success, negative = error code)</field>
            <field type="uint16_t" name="device_certificate_total_len">Total certificate length (across all fragments)</field>
            <field type="uint16_t" name="device_certificate_offset">Byte offset of this fragment</field>
            <field type="uint8_t" name="device_certificate_len">Length of certificate data in this fragment (0-244)</field>
            <field type="uint8_t[244]" name="device_certificate">Device certificate fragment (DER, max 244 bytes per frame)</field>
            <field type="uint8_t" name="key_purpose">0 = signing cert, 1 = encryption cert</field>
        </message>

        <!-- SE05X_ECIES_TEST_REQUEST: Host-initiated ECIES encryption test (host → FC) -->
        <message id="55003" name="SE05X_ECIES_TEST_REQUEST">
            <description>ECIES encryption test request. Host sends its ephemeral P-384 public key and a 32-byte plaintext challenge. The FC encrypts the challenge using ECIES (P-384 ECDH + HKDF-SHA384 + AES-256-CBC + HMAC-SHA384) and returns the result in SE05X_ECIES_TEST_RESPONSE.</description>
            <field type="uint8_t" name="target_system">Target system ID</field>
            <field type="uint8_t" name="target_component">Target component ID</field>
            <field type="uint8_t" name="phase">Test phase: 0=ECIES encrypt (FC encrypts challenge), 1=ECDSA sign (FC signs challenge), 2=session key derivation (FC derives and returns HMAC proof)</field>
            <field type="uint8_t[97]" name="host_public_key">Host P-384 public key (uncompressed: 0x04 || X || Y, 97 bytes). Used in phase 0.</field>
            <field type="uint8_t[32]" name="plaintext">Challenge plaintext (32 random bytes from host). Used in phase 0 and 1.</field>
        </message>

        <!-- SE05X_ECIES_TEST_RESPONSE: FC ECIES encryption result (FC → host) -->
        <message id="55004" name="SE05X_ECIES_TEST_RESPONSE">
            <description>ECIES encryption test response. Contains the FC's ephemeral public key and the encrypted challenge (IV + ciphertext + HMAC-SHA384 tag). The host decrypts by performing ECDH with its private key against the ephemeral public key, then HKDF + AES-CBC-decrypt + HMAC-verify.</description>
            <field type="uint8_t" name="target_system">Target system ID</field>
            <field type="uint8_t" name="target_component">Target component ID</field>
            <field type="int8_t" name="result">0 = success, negative = error code</field>
            <field type="uint8_t" name="phase">Test phase (mirrors request phase)</field>
            <field type="uint8_t[97]" name="ephemeral_public_key">Phase 0: FC ephemeral P-384 public key. Phase 1: ECDSA signature bytes [0..96]. Phase 2: session ephemeral P-384 public key.</field>
            <field type="uint8_t[12]" name="iv">Phase 0: AES-CBC IV. Phase 1: signature bytes [97..103] + signature_len at [7].</field>
            <field type="uint8_t[32]" name="ciphertext">Phase 0: AES-256-CBC encrypted challenge. Phase 1: echo of signed plaintext. Phase 2: unused.</field>
            <field type="uint8_t[48]" name="hmac_tag">Phase 0: HMAC-SHA384 tag. Phase 1: unused. Phase 2: HMAC-SHA384(derived_hmac_key, "PX4-SE05X-SESSION-TEST") proof.</field>
        </message>

        <!-- SE05X_PROVISIONER_KEY: Provisioner encryption public key for session key derivation -->
        <message id="55005" name="SE05X_PROVISIONER_KEY">
            <description>Provisioner P-384 encryption public key. Stored on the SE05x during provisioning. Used for ECDH in session key derivation, enabling the provisioner to decrypt ULog files offline via ECDH(provisioner_priv, boot_ephemeral_pub). Send this before SE05X_PROVISION.</description>
            <field type="uint8_t" name="target_system">Target system ID</field>
            <field type="uint8_t" name="target_component">Target component ID</field>
            <field type="uint8_t[97]" name="provisioner_encryption_key">Provisioner P-384 public key (uncompressed: 0x04 || X || Y, 97 bytes)</field>
        </message>
    </messages>
</mavlink>

Custom init to boostrap the SE05x driver, MAVLink handler and session keys

#!/bin/sh
# SE05x auto-start (baked into ROMFS at build time)
echo "[SE05x ext] Starting se05x driver..."
se05x start
echo "[SE05x ext] se05x rc=$?"
echo "[SE05x ext] Starting se05x_mavlink..."
se05x_mavlink start
echo "[SE05x ext] se05x_mavlink rc=$?"
se05x derive-keys &

Build output demonstrating MAVLink dialect and ROMFS integration

methodmissing@Mac PX4-Autopilot % make px4_fmu-v6xrt_default CONFIG_SYSTEMCMDS_SE05X=y CONFIG_CRYPTO=y CONFIG_MBEDTLS_VERSION=3.4.0 CONFIG_CRYPTO_MBEDTLS=y CONFIG_CLOCK_GETTIME=y CONFIG_GETTIMEOFDAY=y CONFIG_SE05X_DEBUG_LOGS=y EXTERNAL_MODULES_LOCATION=/Users/methodmissing/src/px4-se05x upload
-- PX4_GIT_TAG: v1.18.0-alpha1-75-g26f188d5e9
-- PX4 config file: /Users/methodmissing/src/PX4-Autopilot/boards/px4/fmu-v6xrt/default.px4board
-- PLATFORM nuttx
-- TOOLCHAIN arm-none-eabi
-- ARCHITECTURE cortex-m7
-- ROMFSROOT px4fmu_common
-- IO px4_io-v2_default
-- ETHERNET y
-- SERIAL_GPS1 /dev/ttyS1
-- SERIAL_GPS2 /dev/ttyS3
-- SERIAL_TEL1 /dev/ttyS2
-- SERIAL_TEL2 /dev/ttyS5
-- SERIAL_TEL3 /dev/ttyS6
-- SERIAL_RC /dev/ttyS4
-- ROOT_PATH /fs/microsd
-- PARAM_FILE /fs/mtd_params
-- UAVCAN_INTERFACES 3
-- PWM_FREQ 1000000
-- PX4 config: px4_fmu-v6xrt_default
-- PX4 platform: nuttx
warning: ARCH_CHIP_UNSET (defined at platforms/nuttx/Kconfig:5) was assigned the value 'y' but got the value 'n' -- check dependencies
-- Enabling double FP precision hardware instructions
-- cmake build type: MinSizeRel
-- ccache enabled (export CCACHE_DISABLE=1 to disable)
-- Board forcing alignment
Synchronizing submodule url for 'src/lib/cdrstream/cyclonedds'
Submodule path 'src/lib/cdrstream/cyclonedds': checked out '314887ca403c2fb0a0316add22672102936ed36c'
-- Configuring idlc :/Users/methodmissing/src/PX4-Autopilot/build/px4_fmu-v6xrt_default/msg/idlc
-- Building idlc :/Users/methodmissing/src/PX4-Autopilot/build/px4_fmu-v6xrt_default/msg/idlc
-- External modules: /Users/methodmissing/src/px4-se05x
-- SE05x: Copied mbedtls_config.h to NuttX apps/include/crypto/
-- External MAVLink dialect registered: se05x (from /Users/methodmissing/src/px4-se05x/mavlink/se05x.xml)
-- External MAVLink dialect: se05x (auto-set from common)
-- Unable to determine version from Git, defaulting to version v0.0.0
-- Defaulting MIP_ARCH to cortex-m7
-- C Standard: 99
-- C++ Standard: 14
-- Build Examples: OFF
-- Build Tools: OFF
-- Use Deprecated Macros: ON
-- drivers/px4io: ROMFS including px4_io-v2_default
-- Release build type: MinSizeRel
-- ROMFS: ROMFS/px4fmu_common
-- ROMFS:  Adding platforms/nuttx/init/imxrt/rc.board_arch_defaults -> /etc/init.d/rc.board_arch_defaults
-- ROMFS:  Adding boards/px4/fmu-v6xrt/init/rc.board_defaults -> /etc/init.d/rc.board_defaults
-- ROMFS:  Adding boards/px4/fmu-v6xrt/init/rc.board_sensors -> /etc/init.d/rc.board_sensors
-- ROMFS:  Adding boards/px4/fmu-v6xrt/init/rc.board_mavlink -> /etc/init.d/rc.board_mavlink
-- ROMFS:  Adding ../px4-se05x/init/rc.ext_modules -> /etc/init.d/rc.ext_modules
-- ROMFS:  Adding boards/px4/fmu-v6xrt/extras/px4_io-v2_default.bin -> /etc/extras/px4_io-v2_default.bin
-- Configuring done (4.6s)
-- Generating done (0.8s)
-- Build files have been written to: /Users/methodmissing/src/PX4-Autopilot/build/px4_fmu-v6xrt_default

…AVLink dialect support

…dialects

…VLink dialect registration and handling

DronecodeBot · 2026-05-20T13:52:51Z

This pull request has been mentioned on Dronecode Forum | Open Source Drone Development. There might be relevant details there:

https://discuss.px4.io/t/px4-dev-call-may-20-2026-team-sync-and-community-q-a/48985/3

github-actions · 2026-05-20T13:56:19Z

🔎 FLASH Analysis

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px4_fmu-v6x [Total VM Diff: 760 byte (0.04 %)]

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Updated: 2026-05-20T13:55:55

github-actions · 2026-05-20T14:10:52Z

No broken links found in changed files.

hamishwillee · 2026-05-21T01:19:56Z

+Registered handlers are invoked from the MAVLink receiver thread's `default` switch case.
+Registration is mutex-protected; dispatch is lock-free.
+
+### Outbound Streams


This is cool, but what if I just want to send a message or command, not stream it?

methodmissing added 10 commits May 19, 2026 11:22

mavlink: add external handler and stream registries for out-of-tree M…

8bf6152

…AVLink dialect support

cmake: add mavlink/ directory convention for external module MAVLink …

5b53083

…dialects

Add support for rate intervals

cf80343

Use mutex in mavlink_ext_handler_register

d9b0cdc

Add mavlink_ext_stream_set_interval and use mutex in ext_stream

cad563f

Prefer explicit shared cmake function px4_add_external_mavlink_dialect

bf8f1f6

Introduce support for optional external module auto-start / init scripts

f2d0b99

Add documentation relevant to OOT support for startup sequence and MA…

1255684

…VLink dialect registration and handling

Cleanups

80d1ef6

Reverse boot order so that logging has precedence over OOT module inits

26f188d

methodmissing changed the title ~~Out of tree modules: support external MAVLink handler, stream, and dialect support alongside opt in custom init scripts~~ feat(oot): support external MAVLink handler, stream, and dialect with opt in custom init scripts in Out of Tree modules May 20, 2026

github-actions Bot added the kind:feature Request or change that adds new functionality. label May 20, 2026

farhangnaderi requested review from dakejahl, hamishwillee, julianoes and onur-ozkan May 20, 2026 15:14

dakejahl requested a review from bkueng May 20, 2026 17:40

hamishwillee reviewed May 21, 2026

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feat(oot): support external MAVLink handler, stream, and dialect with opt in custom init scripts in Out of Tree modules#27415

feat(oot): support external MAVLink handler, stream, and dialect with opt in custom init scripts in Out of Tree modules#27415
methodmissing wants to merge 10 commits into
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methodmissing:external-mods-flex

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methodmissing commented May 20, 2026

mavlink: external handler, stream, and dialect support for out-of-tree modules

Summary

Changes

1. External MAVLink handler registry (mavlink_ext_handler.{h,cpp})

2. External MAVLink stream registry (mavlink_ext_stream.{h,cpp})

3. CMake dialect registration (px4_add_external_mavlink_dialect)

4. ROMFS init script injection (ROMFS/CMakeLists.txt, rcS)

Integration points (minimal PX4 source changes)

Design decisions

Testing

Example usage in OOT module

Header file of the MAVLink handler concerns

Custom MAVLink SE05x dialect

Custom init to boostrap the SE05x driver, MAVLink handler and session keys

Build output demonstrating MAVLink dialect and ROMFS integration

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1. External MAVLink handler registry (`mavlink_ext_handler.{h,cpp}`)

2. External MAVLink stream registry (`mavlink_ext_stream.{h,cpp}`)

3. CMake dialect registration (`px4_add_external_mavlink_dialect`)

4. ROMFS init script injection (`ROMFS/CMakeLists.txt`, `rcS`)