Tries to emulate Taranis HID descriptor. Didn't work for problematic programs, either.

src/foohid.c

@@ -12,6 +12,7 @@
 #include <signal.h>
 #include <string.h>
 #include <unistd.h>
+#include <stdlib.h>
 
 #include <IOKit/IOKitLib.h>
 
@@ -33,16 +34,25 @@
 #define FOOHID_DESTROY 1
 #define FOOHID_SEND 2
 #define FOOHID_LIST 3
-#define VIRTUAL_DEVICE_NAME "Virtual Serial Transmitter"
-#define VIRTUAL_DEVICE_SERIAL "SN 123456"
+
+#define VIRTUAL_DEVICE_NAME "FrSky Joystick"
+#define VIRTUAL_DEVICE_SERIAL "00000000001B"
+#define VIRTUAL_VID 0x0483
+#define VIRTUAL_PID 0x5710
 
 struct gamepad_report_t {
-    int16_t leftX;
-    int16_t leftY;
-    int16_t rightX;
-    int16_t rightY;
-    int16_t aux1;
-    int16_t aux2;
+    //bit 0 - button 1, bit 1 - button 2, ..., mapped to channels 9-16, on if channel > 0
+    uint8_t buttons1;
+    uint8_t buttons2; // mapped to channels 17-24, on if channel > 0
+    uint8_t buttons3; // mapped to channels 25-32, on if channel > 0
+    int8_t X;  //analog value, mapped to channel 1
+    int8_t Y;  //analog value, mapped to channel 2
+    int8_t Z;  //analog value, mapped to channel 3
+    int8_t Rx; //analog value, mapped to channel 4
+    int8_t Ry; //analog value, mapped to channel 5
+    int8_t Rz; //analog value, mapped to channel 6
+    int8_t S1; //analog value, mapped to channel 7
+    int8_t S2; //analog value, mapped to channel 8
 };
 
 static int running = 1;
@@ -53,33 +63,89 @@ static io_connect_t connect;
 static uint64_t input[input_count];
 static struct gamepad_report_t gamepad;
 
-/*
- * This is my USB HID Descriptor for this emulated Gamepad.
- * For more informations refer to:
- * http://eleccelerator.com/tutorial-about-usb-hid-report-descriptors/
- * http://www.usb.org/developers/hidpage#HID%20Descriptor%20Tool
- */
-static char report_descriptor[36] = {
-    0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)
-    0x09, 0x05,                    // USAGE (Game Pad)
-    0xa1, 0x01,                    // COLLECTION (Application)
-    0xa1, 0x00,                    //   COLLECTION (Physical)
+// From Taranis:
+// https://github.com/opentx/opentx/blob/03b65b06b6cec2d2b64dfb0f436eda155274841d/radio/src/targets/common/arm/stm32/usbd_hid_joystick.c
+static const uint8_t report_descriptor[] = {
     0x05, 0x01,                    //     USAGE_PAGE (Generic Desktop)
-    0x09, 0x30,                    //     USAGE (X)
-    0x09, 0x31,                    //     USAGE (Y)
-    0x09, 0x32,                    //     USAGE (Z)
-    0x09, 0x33,                    //     USAGE (Rx)
-    0x09, 0x34,                    //     USAGE (Ry)
-    0x09, 0x35,                    //     USAGE (Rz)
-    0x16, 0x01, 0xfe,              //     LOGICAL_MINIMUM (-511)
-    0x26, 0xff, 0x01,              //     LOGICAL_MAXIMUM (511)
-    0x75, 0x10,                    //     REPORT_SIZE (16)
-    0x95, 0x06,                    //     REPORT_COUNT (6)
-    0x81, 0x02,                    //     INPUT (Data,Var,Abs)
-    0xc0,                          //     END_COLLECTION
-    0xc0                           // END_COLLECTION
+    0x09, 0x05,                    //     USAGE (Game Pad)
+    0xa1, 0x01,                    //     COLLECTION (Application)
+    0xa1, 0x00,                    //       COLLECTION (Physical)
+    0x05, 0x09,                    //         USAGE_PAGE (Button)
+    0x19, 0x01,                    //         USAGE_MINIMUM (Button 1)
+    0x29, 0x18,                    //         USAGE_MAXIMUM (Button 24)
+    0x15, 0x00,                    //         LOGICAL_MINIMUM (0)
+    0x25, 0x01,                    //         LOGICAL_MAXIMUM (1)
+    0x95, 0x18,                    //         REPORT_COUNT (24)
+    0x75, 0x01,                    //         REPORT_SIZE (1)
+    0x81, 0x02,                    //         INPUT (Data,Var,Abs)
+    0x05, 0x01,                    //         USAGE_PAGE (Generic Desktop)
+    0x09, 0x30,                    //         USAGE (X)
+    0x09, 0x31,                    //         USAGE (Y)
+    0x09, 0x32,                    //         USAGE (Z)
+    0x09, 0x33,                    //         USAGE (Rx)
+    0x09, 0x34,                    //         USAGE (Ry)
+    0x09, 0x35,                    //         USAGE (Rz)
+    0x09, 0x36,                    //         USAGE (Slider)
+    0x09, 0x36,                    //         USAGE (Slider)
+    0x15, 0x81,                    //         LOGICAL_MINIMUM (-127)
+    0x25, 0x7f,                    //         LOGICAL_MAXIMUM (127)
+    0x75, 0x08,                    //         REPORT_SIZE (8)
+    0x95, 0x08,                    //         REPORT_COUNT (8)
+    0x81, 0x02,                    //         INPUT (Data,Var,Abs)
+    0xc0,                          //       END_COLLECTION
+    0xc0                           //     END_COLLECTION
 };
 
+static int foohidPrintDevices() {
+    uint32_t output_count = 2;
+    uint64_t output[2] = { 0, 0 };
+
+	uint16_t buf_len = 4096;
+	char *buf = malloc(buf_len);
+	if (!buf) {
+        printf("memory error\n");
+		return 1;
+	}
+
+    uint64_t input[2];
+	while (1) {
+        input[0] = (uint64_t) buf;
+        input[1] = (uint64_t) buf_len;
+        kern_return_t ret = IOConnectCallScalarMethod(connect, FOOHID_LIST, input, 2, output, &output_count);
+        if (ret != KERN_SUCCESS) {
+            free(buf);
+            printf("unable to list hid devices\n");
+            return 1;
+        }
+
+        // all is fine
+        if (output[0] == 0) {
+            printf("--\n");
+            printf("fooHID devices: (%llu)\n", output[1]);
+            char *ptr = buf;
+            for(uint64_t i = 0; i < output[1]; i++) {
+                printf("%s\n", ptr);
+                ptr += strlen(ptr) + 1;
+            }
+            printf("--\n");
+            free(buf);
+            return ret;
+        }
+
+        // realloc memory
+        buf_len = output[0];
+        char *tmp = realloc(buf, buf_len);
+        if (!tmp) {
+            free(buf);
+            printf("unable to allocate memory\n");
+            return 1;
+        }
+        buf = tmp;
+	}
+
+    return 0;
+}
+
 static int foohidInit() {
     printf("Searching for foohid Kernel extension...\n");
 
@@ -105,6 +171,7 @@ static int foohidInit() {
         return 1;
     }
 
+    //foohidPrintDevices();
     printf("Creating virtual HID device...\n");
 
     input[0] = (uint64_t)strdup(VIRTUAL_DEVICE_NAME);
@@ -116,8 +183,8 @@ static int foohidInit() {
     input[4] = (uint64_t)strdup(VIRTUAL_DEVICE_SERIAL);
     input[5] = strlen((char*)input[4]);
 
-    input[6] = (uint64_t)2; // vendor ID
-    input[7] = (uint64_t)3; // device ID
+    input[6] = (uint64_t)VIRTUAL_VID;
+    input[7] = (uint64_t)VIRTUAL_PID;
 
     ret = IOConnectCallScalarMethod(connect, FOOHID_CREATE, input, input_count, NULL, 0);
     if (ret != KERN_SUCCESS) {
@@ -144,22 +211,12 @@ static void foohidSend(uint16_t *data) {
         }
     }
 
-    gamepad.leftX = data[3] - 511;
-    gamepad.leftY = data[2] - 511;
-    gamepad.rightX = data[0] - 511;
-    gamepad.rightY = data[1] - 511;
-    gamepad.aux1 = data[4] - 511;
-    gamepad.aux2 = data[5] - 511;
-
-    /*
-    printf("Sending data packet:\n");
-    printf("Left X: %d\n", gamepad.leftX);
-    printf("Left Y: %d\n", gamepad.leftY);
-    printf("Right X: %d\n", gamepad.rightX);
-    printf("Right Y: %d\n", gamepad.rightY);
-    printf("Aux 1: %d\n", gamepad.aux1);
-    printf("Aux 2: %d\n", gamepad.aux2);
-    */
+    gamepad.X = (data[3] - 511) / 4;
+    gamepad.Y = (data[2] - 511) / 4;
+    gamepad.Z = (data[0] - 511) / 4;
+    gamepad.Rx = (data[1] - 511) / 4;
+    gamepad.Ry = (data[4] - 511) / 4;
+    gamepad.Rz = (data[5] - 511) / 4;
 
     input[2] = (uint64_t)&gamepad;
     input[3] = sizeof(struct gamepad_report_t);