From ee3b7b218248c8853860572dab5f4771b60a2804 Mon Sep 17 00:00:00 2001
From: scuti <scuti@teknik.io>
Date: Tue, 28 Sep 2021 20:34:21 -0700
Subject: [PATCH] scuti/hotplug (#11)

Added hotplugging support.
---
 hanvon-libusb.c | 130 ++++++++++++++++++++++++++++++------------------
 1 file changed, 82 insertions(+), 48 deletions(-)

diff --git a/hanvon-libusb.c b/hanvon-libusb.c
index 8c00497..405615f 100644
--- a/hanvon-libusb.c
+++ b/hanvon-libusb.c
@@ -447,48 +447,78 @@ int init_ctrl(struct libusb_device * const d,
     return is_ok;
 }
 
-int handle_device_lusb(libusb_device *d) {
-    libusb_device_handle *h;
-    int status = libusb_open(d, &h);
-    if (status < 0 || h == NULL) {
-        printf("Error opening device, %i.\n", status);
-        return 0;
+// GLOBAL: for main and hotplug_callback
+static int HOT_COUNT = 0; 
+static struct libusb_transfer *TX = NULL;
+void loop() {
+    int status = 0;
+    int LAST_HOT_COUNT = 0;
+    while (1) {
+        if (TX != NULL && TX->dev_handle != 0) {
+            status = libusb_submit_transfer(TX);
+        }
+        if (status < 0 && LAST_HOT_COUNT != HOT_COUNT) { 
+            printf("\nwarning: usb transfer status = %i\n", status);
+            //continue;
+        }
+        LAST_HOT_COUNT = HOT_COUNT;
+        libusb_handle_events_completed(NULL, NULL);
     }
-    struct libevdev         *evdev = NULL;
-    struct libevdev_uinput  *uidev = NULL;
-    printf("handle_device: %x\n", uidev);
-    if (init_ctrl(d, &evdev, &uidev) < 0) {
-        return 0;
-    }
-    if (evdev == NULL || uidev == NULL) {
-        printf("Error initializing controls, %x, %x.\n", evdev, uidev);
-        return 0;
-    }
-    struct libusb_transfer *tx;
-    const int ENDPOINT_ADDR = 0x81;  // bEndpointAddress from lsusb -v
-    //AM_PACKET_LEN = 10;            // wMaxPacketSize from lsusb -v
-    unsigned char buffer[AM_PACKET_LEN];
+}
 
-    // Allocate memory for transfer, configure, then submit
-    tx = libusb_alloc_transfer(0);
-    libusb_fill_interrupt_transfer(
-                    tx,
-                    h, 
+// TODO: make scuti explain why this is called twice
+int hotplug_callback(struct libusb_context *ctx, struct libusb_device *dev,
+                     libusb_hotplug_event event, void *user_data) {
+
+    static libusb_device_handle *dev_handle;
+    static struct libevdev_uinput  *uidev = NULL;
+    static struct libevdev         *evdev = NULL;
+    struct libusb_device_descriptor desc;
+    int rc;
+    libusb_get_device_descriptor(dev, &desc);
+    if (LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED == event) {
+        // check if the device supported
+        libusb_device *devs[1] = {dev};
+        int index = find_device(devs, 1);
+        if (index < 0) {
+            printf("INFO: Detected Hanvon device, but it is not supported.\n");
+        } else {
+            // libusb functions that accept libusb_device = SAFE
+            // submit asynchronous transfers              = SAFE
+            // other functions that accept device handle  = NOT SAFE
+            libusb_open(dev, &dev_handle);
+            if (init_ctrl(dev, &evdev, &uidev) < 0) {
+                printf("Error: Could not initialize controls.\n");
+                exit(EXIT_FAILURE);
+                
+            }
+            const int ENDPOINT_ADDR = 0x81;  // bEndpointAddress from lsusb -v
+            //AM_PACKET_LEN = 10;            // wMaxPacketSize from lsusb -v
+            unsigned char buffer[AM_PACKET_LEN];
+            TX = libusb_alloc_transfer(0);
+            libusb_fill_interrupt_transfer(
+                    TX,
+                    dev_handle, 
                     ENDPOINT_ADDR, 
                     buffer, 
                     AM_PACKET_LEN,
                     callback_default,
                     uidev,     // extra data to send in tx    
-                    130);      // timeout in milliseconds
-    do {
-        status = libusb_submit_transfer(tx);
-        if (status < 0 ) {
-            printf("warning: usb transfer status = %i\n", status);
-            //continue;
+                    130        // timeout in milliseconds
+            );
+        }
+    } else if (LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT) {
+        if (dev_handle) {
+            libusb_close(dev_handle);
+            dev_handle = NULL;
+            libevdev_uinput_destroy(uidev);
+            libusb_free_transfer(TX);
+            TX = NULL;
+        }
+    } else {
+        printf ("INFO: Device left, but handle did not exist.\n");
     }
-    libusb_handle_events(NULL);
-    } while (1);
-    libevdev_uinput_destroy(uidev);
+    HOT_COUNT++;
     return 0;
 }
 
@@ -496,25 +526,29 @@ int main() {
 #define UNREF_DEVICE 1 
 #define KEEP_DEVICE_REF 0 
 
-    libusb_device ** devs;
     int r = libusb_init(NULL);
     if (r < 0) {
         return r;
     } 
-    int count = libusb_get_device_list(NULL, &devs);
-    if (count < 0) {
+    libusb_hotplug_callback_handle callback_handle;
+    int rc;
+    rc = libusb_hotplug_register_callback(
+        NULL, 
+        LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED |
+        LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT, 
+        0, 
+        VENDOR_ID_HANVON,         // VENDOR
+        LIBUSB_HOTPLUG_MATCH_ANY, // PRODUCT
+        LIBUSB_HOTPLUG_MATCH_ANY, // DEV CLASS
+        hotplug_callback, 
+        NULL,
+        &callback_handle
+    );
+    if (rc != LIBUSB_SUCCESS) {
+        printf("Error creating a hotplug callback\n");
         libusb_exit(NULL);
-        return count;
+        return EXIT_FAILURE;
     }
-    int index = find_device(devs, count);
-    if (index < 0) {
-        printf("Device not plugged in\n");
-        libusb_exit(NULL);
-        return 0;
-    }
-    libusb_device *device = devs[index];
-    libusb_free_device_list (devs, UNREF_DEVICE);
-    int s = handle_device_lusb(device);
-    libusb_exit(NULL);
+    loop();
     return 0;
 }