Extract USB handling from AOA

The AOA code handled both USB initialization and AOA commands/events.
Extract USB-related code to a separate file and structure.

PR #2974 <https://github.com/Genymobile/scrcpy/pull/2974>

app/meson.build

@@ -78,6 +78,7 @@ if usb_support
         'src/usb/aoa_hid.c',
         'src/usb/hid_keyboard.c',
         'src/usb/hid_mouse.c',
+        'src/usb/usb.c',
     ]
 endif
 

app/src/usb/aoa_hid.c

@@ -50,74 +50,6 @@ log_libusb_error(enum libusb_error errcode) {
     LOGW("libusb error: %s", libusb_strerror(errcode));
 }
 
-static bool
-accept_device(libusb_device *device, const char *serial) {
-    // do not log any USB error in this function, it is expected that many USB
-    // devices available on the computer have permission restrictions
-
-    struct libusb_device_descriptor desc;
-    int result = libusb_get_device_descriptor(device, &desc);
-    if (result < 0 || !desc.iSerialNumber) {
-        return false;
-    }
-
-    libusb_device_handle *handle;
-    result = libusb_open(device, &handle);
-    if (result < 0) {
-        return false;
-    }
-
-    char buffer[128];
-    result = libusb_get_string_descriptor_ascii(handle, desc.iSerialNumber,
-                                                (unsigned char *) buffer,
-                                                sizeof(buffer));
-    libusb_close(handle);
-    if (result < 0) {
-        return false;
-    }
-
-    buffer[sizeof(buffer) - 1] = '\0'; // just in case
-
-    // accept the device if its serial matches
-    return !strcmp(buffer, serial);
-}
-
-static libusb_device *
-sc_aoa_find_usb_device(const char *serial) {
-    if (!serial) {
-        return NULL;
-    }
-
-    libusb_device **list;
-    libusb_device *result = NULL;
-    ssize_t count = libusb_get_device_list(NULL, &list);
-    if (count < 0) {
-        log_libusb_error((enum libusb_error) count);
-        return NULL;
-    }
-
-    for (size_t i = 0; i < (size_t) count; ++i) {
-        libusb_device *device = list[i];
-
-        if (accept_device(device, serial)) {
-            result = libusb_ref_device(device);
-            break;
-        }
-    }
-    libusb_free_device_list(list, 1);
-    return result;
-}
-
-static int
-sc_aoa_open_usb_handle(libusb_device *device, libusb_device_handle **handle) {
-    int result = libusb_open(device, handle);
-    if (result < 0) {
-        log_libusb_error((enum libusb_error) result);
-        return result;
-    }
-    return 0;
-}
-
 bool
 sc_aoa_init(struct sc_aoa *aoa, const char *serial,
             struct sc_acksync *acksync) {
@@ -133,31 +65,16 @@ sc_aoa_init(struct sc_aoa *aoa, const char *serial,
         goto error_destroy_mutex;
     }
 
-    if (libusb_init(&aoa->usb_context) != LIBUSB_SUCCESS) {
+    bool ok = sc_usb_init(&aoa->usb, serial);
+    if (!ok) {
         goto error_destroy_cond;
     }
 
-    aoa->usb_device = sc_aoa_find_usb_device(serial);
-    if (!aoa->usb_device) {
-        LOGW("USB device of serial %s not found", serial);
-        goto error_exit_libusb;
-    }
-
-    if (sc_aoa_open_usb_handle(aoa->usb_device, &aoa->usb_handle) < 0) {
-        LOGW("Open USB handle failed");
-        goto error_unref_device;
-        return false;
-    }
-
     aoa->stopped = false;
     aoa->acksync = acksync;
 
     return true;
 
-error_unref_device:
-    libusb_unref_device(aoa->usb_device);
-error_exit_libusb:
-    libusb_exit(aoa->usb_context);
 error_destroy_cond:
     sc_cond_destroy(&aoa->event_cond);
 error_destroy_mutex:
@@ -173,9 +90,7 @@ sc_aoa_destroy(struct sc_aoa *aoa) {
         sc_hid_event_destroy(&event);
     }
 
-    libusb_close(aoa->usb_handle);
+    sc_usb_destroy(&aoa->usb);
-    libusb_unref_device(aoa->usb_device);
-    libusb_exit(aoa->usb_context);
     sc_cond_destroy(&aoa->event_cond);
     sc_mutex_destroy(&aoa->mutex);
 }
@@ -192,7 +107,7 @@ sc_aoa_register_hid(struct sc_aoa *aoa, uint16_t accessory_id,
     uint16_t index = report_desc_size;
     unsigned char *buffer = NULL;
     uint16_t length = 0;
-    int result = libusb_control_transfer(aoa->usb_handle, request_type, request,
+    int result = libusb_control_transfer(aoa->usb.handle, request_type, request,
                                          value, index, buffer, length,
                                          DEFAULT_TIMEOUT);
     if (result < 0) {
@@ -228,7 +143,7 @@ sc_aoa_set_hid_report_desc(struct sc_aoa *aoa, uint16_t accessory_id,
     // libusb_control_transfer expects a pointer to non-const
     unsigned char *buffer = (unsigned char *) report_desc;
     uint16_t length = report_desc_size;
-    int result = libusb_control_transfer(aoa->usb_handle, request_type, request,
+    int result = libusb_control_transfer(aoa->usb.handle, request_type, request,
                                          value, index, buffer, length,
                                          DEFAULT_TIMEOUT);
     if (result < 0) {
@@ -270,7 +185,7 @@ sc_aoa_send_hid_event(struct sc_aoa *aoa, const struct sc_hid_event *event) {
     uint16_t index = 0;
     unsigned char *buffer = event->buffer;
     uint16_t length = event->size;
-    int result = libusb_control_transfer(aoa->usb_handle, request_type, request,
+    int result = libusb_control_transfer(aoa->usb.handle, request_type, request,
                                          value, index, buffer, length,
                                          DEFAULT_TIMEOUT);
     if (result < 0) {
@@ -292,7 +207,7 @@ sc_aoa_unregister_hid(struct sc_aoa *aoa, const uint16_t accessory_id) {
     uint16_t index = 0;
     unsigned char *buffer = NULL;
     uint16_t length = 0;
-    int result = libusb_control_transfer(aoa->usb_handle, request_type, request,
+    int result = libusb_control_transfer(aoa->usb.handle, request_type, request,
                                          value, index, buffer, length,
                                          DEFAULT_TIMEOUT);
     if (result < 0) {

app/src/usb/aoa_hid.h

@@ -6,6 +6,7 @@
 
 #include <libusb-1.0/libusb.h>
 
+#include "usb.h"
 #include "util/acksync.h"
 #include "util/cbuf.h"
 #include "util/thread.h"
@@ -29,9 +30,7 @@ sc_hid_event_destroy(struct sc_hid_event *hid_event);
 struct sc_hid_event_queue CBUF(struct sc_hid_event, 64);
 
 struct sc_aoa {
-    libusb_context *usb_context;
+    struct sc_usb usb;
-    libusb_device *usb_device;
-    libusb_device_handle *usb_handle;
     sc_thread thread;
     sc_mutex mutex;
     sc_cond event_cond;

app/src/usb/usb.c

@@ -0,0 +1,112 @@
+#include "usb.h"
+
+#include <assert.h>
+
+#include "util/log.h"
+
+static inline void
+log_libusb_error(enum libusb_error errcode) {
+    LOGW("libusb error: %s", libusb_strerror(errcode));
+}
+
+static bool
+accept_device(libusb_device *device, const char *serial) {
+    // Do not log any USB error in this function, it is expected that many USB
+    // devices available on the computer have permission restrictions
+
+    struct libusb_device_descriptor desc;
+    int result = libusb_get_device_descriptor(device, &desc);
+    if (result < 0 || !desc.iSerialNumber) {
+        return false;
+    }
+
+    libusb_device_handle *handle;
+    result = libusb_open(device, &handle);
+    if (result < 0) {
+        return false;
+    }
+
+    char buffer[128];
+    result = libusb_get_string_descriptor_ascii(handle, desc.iSerialNumber,
+                                                (unsigned char *) buffer,
+                                                sizeof(buffer));
+    libusb_close(handle);
+    if (result < 0) {
+        return false;
+    }
+
+    buffer[sizeof(buffer) - 1] = '\0'; // just in case
+
+    // Accept the device if its serial matches
+    return !strcmp(buffer, serial);
+}
+
+static libusb_device *
+sc_usb_find_device(const char *serial) {
+    if (!serial) {
+        return NULL;
+    }
+
+    libusb_device **list;
+    libusb_device *result = NULL;
+    ssize_t count = libusb_get_device_list(NULL, &list);
+    if (count < 0) {
+        log_libusb_error((enum libusb_error) count);
+        return NULL;
+    }
+
+    for (size_t i = 0; i < (size_t) count; ++i) {
+        libusb_device *device = list[i];
+
+        if (accept_device(device, serial)) {
+            result = libusb_ref_device(device);
+            break;
+        }
+    }
+
+    libusb_free_device_list(list, 1);
+    return result;
+}
+
+static libusb_device_handle *
+sc_usb_open_handle(libusb_device *device) {
+    libusb_device_handle *handle;
+    int result = libusb_open(device, &handle);
+    if (result < 0) {
+        log_libusb_error((enum libusb_error) result);
+        return NULL;
+    }
+    return handle;
+ }
+
+bool
+sc_usb_init(struct sc_usb *usb, const char *serial) {
+    // There is only one device, initialize the context here
+    if (libusb_init(&usb->context) != LIBUSB_SUCCESS) {
+        return false;
+    }
+
+    usb->device = sc_usb_find_device(serial);
+    if (!usb->device) {
+        LOGW("USB device %s not found", serial);
+        libusb_exit(usb->context);
+        return false;
+    }
+
+    usb->handle = sc_usb_open_handle(usb->device);
+    if (!usb->handle) {
+        LOGW("Could not open USB device %s", serial);
+        libusb_unref_device(usb->device);
+        libusb_exit(usb->context);
+        return false;
+    }
+
+    return true;
+}
+
+void
+sc_usb_destroy(struct sc_usb *usb) {
+    libusb_close(usb->handle);
+    libusb_unref_device(usb->device);
+    libusb_exit(usb->context);
+}

app/src/usb/usb.h

@@ -0,0 +1,21 @@
+#ifndef SC_USB_H
+#define SC_USB_H
+
+#include "common.h"
+
+#include <stdbool.h>
+#include <libusb-1.0/libusb.h>
+
+struct sc_usb {
+    libusb_context *context;
+    libusb_device *device;
+    libusb_device_handle *handle;
+};
+
+bool
+sc_usb_init(struct sc_usb *usb, const char *serial);
+
+void
+sc_usb_destroy(struct sc_usb *usb);
+
+#endif