Variable length frames, part1: USB Host -> Pm3

include/usb_cmd.h

@@ -35,6 +35,27 @@ typedef struct {
     } d;
 } PACKED UsbCommand;
 
+typedef struct {
+    uint32_t magic;
+    uint32_t length;  // length of the variable part, 0 if none.
+} PACKED UsbCommandNGPreamble;
+
+#define USB_PREAMBLE_MAGIC 0xAA5500FF
+
+typedef struct {
+    uint64_t cmd;
+    uint64_t arg[3];
+} PACKED UsbCommandNG;
+
+typedef struct {
+    uint32_t crc;
+    uint32_t magic;
+} PACKED UsbCommandNGPostamble;
+
+#define USB_POSTAMBLE_MAGIC 0xFF0055AA
+
+extern bool use_cmd_ng;
+
 #ifdef WITH_FPC_HOST
 // "Session" flag, to tell via which interface next msgs should be sent: USB or FPC USART
 extern bool reply_via_fpc;