usb_device_detection: Added support for detecting basestation un/plugs

build.sh

@@ -2,9 +2,9 @@
 
 set -ex;
 
-SOURCES="main.c output_manager.c accel_monitor.c"
+SOURCES="main.c output_manager.c accel_monitor.c usb_device_detection.c"
 CFLAGS="-std=c2x -Wall -Wextra -pedantic $CFLAGS"
-LIBS="-lwayland-client protocol/wlr-output-management-unstable-v1.c"
+LIBS="-lwayland-client -lusb-1.0 protocol/wlr-output-management-unstable-v1.c"
 OUTPUT=miix-wlr
 
 clang $CFLAGS $LIBS $SOURCES -o $OUTPUT

main.c

@@ -1,9 +1,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-#include "output_manager.h"
+#include <libusb-1.0/libusb.h>
 
 #include "accel_monitor.h"
+#include "output_manager.h"
+#include "usb_device_detection.h"
 
 static enum wl_output_transform const SENSOR_TO_OUTPUT_ROTATION[] = {
     [ACCEL_ROTATION_0DEG]   = WL_OUTPUT_TRANSFORM_270,
@@ -16,6 +18,9 @@ static char const* const DEFAULT_OUTPUT = "DSI-1";
 static char const* const DEFAULT_MOTION_SENSOR =
     "/sys/bus/iio/devices/iio:device0";
 
+static uint16_t const BASESTATION_VENDOR_ID  = 0x048d;
+static uint16_t const BASESTATION_PRODUCT_ID = 0x8911;
+
 static enum accel_rotation last_accel_rotation = ACCEL_ROTATION_NO_CHANGE;
 
 int main(int, char**)
@@ -27,11 +32,25 @@ int main(int, char**)
 		return -1;
 	}
 
+	struct usb_detector* base_station_detector =
+	    create_detector(BASESTATION_VENDOR_ID, BASESTATION_PRODUCT_ID);
+
 	struct miix_wlr_state* state = miix_wlr_init();
 
 	for (;;) {
 		if (!monitor->data_is_ready) continue;
 
+		if (base_station_detector && base_station_detector->is_connected) {
+			if (last_accel_rotation != ACCEL_ROTATION_0DEG) {
+				miix_wlr_head_set_transform(
+				    state,
+				    DEFAULT_OUTPUT,
+				    SENSOR_TO_OUTPUT_ROTATION[ACCEL_ROTATION_0DEG]);
+				last_accel_rotation = ACCEL_ROTATION_0DEG;
+			}
+			continue;
+		}
+
 		enum accel_rotation rotation = accel_get_current_rotation(monitor);
 		if (rotation == ACCEL_ROTATION_NO_CHANGE ||
 		    rotation == last_accel_rotation)
@@ -42,5 +61,6 @@ int main(int, char**)
 	}
 
 	accel_stop_monitor(monitor);
+	destroy_detector(base_station_detector);
 	miix_wlr_cleanup(state);
 }

usb_device_detection.c

@@ -0,0 +1,99 @@
+#include "usb_device_detection.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int hotplug_callback(struct libusb_context*,
+                     struct libusb_device*,
+                     libusb_hotplug_event event,
+                     void*                user_data)
+{
+	struct usb_detector* detector = user_data;
+
+	if (event == LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED)
+		detector->is_connected = true;
+	else if (event == LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT)
+		detector->is_connected = false;
+	else
+		printf("Unexpected USB device event %d\n", event);
+
+	return 0;
+}
+
+static int libusb_event_handler(void* data)
+{
+	struct usb_detector* detector = data;
+
+	while (!detector->event_handler_should_exit) {
+		thrd_sleep(&(struct timespec){.tv_sec = 1}, NULL);
+		libusb_handle_events(detector->usb_context);
+	}
+
+	return 0;
+}
+
+struct usb_detector* create_detector(uint16_t vendor_id, uint16_t product_id)
+{
+
+	struct libusb_context* usb_context;
+	libusb_init(&usb_context);
+
+	if (!usb_context) {
+		fprintf(stderr,
+		        "Couldn't get USB contexxt. Device detection will not work\n");
+		return 0;
+	}
+
+	struct usb_detector* detector = calloc(1, sizeof(struct usb_detector));
+	detector->usb_context         = usb_context;
+
+	if (libusb_hotplug_register_callback(detector->usb_context,
+	                                     LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED |
+	                                         LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT,
+	                                     LIBUSB_HOTPLUG_ENUMERATE,
+	                                     vendor_id,
+	                                     product_id,
+	                                     LIBUSB_HOTPLUG_MATCH_ANY,
+	                                     hotplug_callback,
+	                                     detector,
+	                                     &detector->hotplug_handle) !=
+	    LIBUSB_SUCCESS) {
+
+		fprintf(stderr,
+		        "Couldn't register usb hotplug listener. Device detection "
+		        "will not work.\n");
+		free(detector);
+		return 0;
+	}
+
+	detector->is_connected              = false;
+	detector->event_handler_should_exit = false;
+
+	if (thrd_create(&detector->event_handler_thread,
+	                &libusb_event_handler,
+	                detector) != thrd_success) {
+		fprintf(stderr,
+		        "Couldn't start event handler. Device detection will not "
+		        "work.\n");
+		free(detector);
+		return 0;
+	}
+
+	return detector;
+}
+
+void destroy_detector(struct usb_detector* detector)
+{
+	libusb_hotplug_deregister_callback(detector->usb_context,
+	                                   detector->hotplug_handle);
+
+	detector->event_handler_should_exit = true;
+	if (thrd_join(detector->event_handler_thread, 0) != thrd_success)
+		fprintf(stderr,
+		        "Couldn't join with usb event handler thread, something went "
+		        "really wrong, we likely won't exit cleanly\n");
+
+	libusb_exit(detector->usb_context);
+
+	free(detector);
+}

usb_device_detection.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <stdatomic.h>
+#include <stdint.h>
+#include <threads.h>
+
+#include <libusb-1.0/libusb.h>
+
+struct usb_detector {
+	atomic_bool is_connected;
+
+	atomic_bool event_handler_should_exit;
+	thrd_t      event_handler_thread;
+
+	struct libusb_context*         usb_context;
+	libusb_hotplug_callback_handle hotplug_handle;
+};
+
+struct usb_detector* create_detector(uint16_t vendor_id, uint16_t product_id);
+void                 destroy_detector(struct usb_detector*);