Gave up on using bitfields

2 files changed, 15 insertions, 8 deletions

diff --git a/src/modules/mavlink/mavlink_ftp.cpp b/src/modules/mavlink/mavlink_ftp.cpp
index f4a7bc101..5b65dc369 100644
--- a/src/modules/mavlink/mavlink_ftp.cpp
+++ b/src/modules/mavlink/mavlink_ftp.cpp
@@ -122,6 +122,9 @@ MavlinkFTP::_worker(Request *req)
 	// check request CRC to make sure this is one of ours
 	messageCRC = hdr->crc32;
 	hdr->crc32 = 0;
+	hdr->padding[0] = 0;
+	hdr->padding[1] = 0;
+	hdr->padding[2] = 0;
 	if (crc32(req->rawData(), req->dataSize()) != messageCRC) {
 		errorCode = kErrNoRequest;
 		goto out;
@@ -203,6 +206,9 @@ MavlinkFTP::_reply(Request *req)
 
 	// message is assumed to be already constructed in the request buffer, so generate the CRC
 	hdr->crc32 = 0;
+	hdr->padding[0] = 0;
+	hdr->padding[1] = 0;
+	hdr->padding[2] = 0;
 	hdr->crc32 = crc32(req->rawData(), req->dataSize());
 
 	// then pack and send the reply back to the request source
diff --git a/src/modules/mavlink/mavlink_ftp.h b/src/modules/mavlink/mavlink_ftp.h
index cf9ea0c07..1dd8f102e 100644
--- a/src/modules/mavlink/mavlink_ftp.h
+++ b/src/modules/mavlink/mavlink_ftp.h
@@ -71,16 +71,17 @@ private:
 
 	static MavlinkFTP	*_server;
 
-	/// @brief This structure is sent in the payload portion of the file transfer protocol mavlink message.
-	/// This structure is layed out such that it should not require any special compiler packing to not consume extra space.
+	/// @brief Trying to pack structures across differing compilers is questionable for Clients, so we pad the
+	/// structure ourselves to 32 bit alignment which should get us what we want.
 	struct RequestHeader
         {
-		uint16_t        seqNumber;  ///< sequence number for message
-		unsigned int    session:4;  ///< Session id for read and write commands
-		unsigned int    opcode:4;   ///< Command opcode
-		uint8_t         size;       ///< Size of data
-		uint32_t        crc32;      ///< CRC for entire Request structure, with crc32 set to 0
-		uint32_t        offset;     ///< Offsets for List and Read commands
+		uint16_t	seqNumber;  ///< sequence number for message
+		uint8_t		session;    ///< Session id for read and write commands
+		uint8_t		opcode;     ///< Command opcode
+		uint8_t		size;       ///< Size of data
+		uint8_t		padding[3];
+		uint32_t	crc32;      ///< CRC for entire Request structure, with crc32 and padding set to 0
+		uint32_t	offset;     ///< Offsets for List and Read commands
 		uint8_t		data[];
         };