Get *basic* USB report sending working.

src/usb_hid.c

@@ -0,0 +1,81 @@
+
+#include <device.h>
+
+#include <usb/usb_device.h>
+#include <usb/class/usb_hid.h>
+
+LOG_MODULE_REGISTER(zmk_usb_hid, CONFIG_ZMK_USB_HID_LOG_LEVEL);
+
+static const u8_t hid_report_desc[] = HID_KEYBOARD_REPORT_DESC();
+static enum usb_dc_status_code usb_status;
+
+static struct device *hid_dev;
+static u8_t report[8] = { 0x00, 0x00 };
+
+#define KEY_OFFSET 0x02
+#define MAX_KEYS 6
+
+int zmk_usb_hid_press_key(enum hid_kbd_code code)
+{
+	if (usb_status == USB_DC_SUSPEND) {
+		return usb_wakeup_request();
+	}
+
+	for (int idx = 0; idx < MAX_KEYS; idx++) {
+		if (report[idx + KEY_OFFSET] != 0U) {
+			continue;
+		}
+
+		report[idx + KEY_OFFSET] = code;
+
+		return hid_int_ep_write(hid_dev, report, sizeof(report), NULL);
+	}
+
+	return -EINVAL;
+}
+
+int zmk_usb_hid_release_key(enum hid_kbd_code code)
+{
+	for (int idx = 0; idx < MAX_KEYS; idx++) {
+		if (report[idx + KEY_OFFSET] != code) {
+			continue;
+		}
+
+		report[idx + KEY_OFFSET] = 0U;
+
+		return hid_int_ep_write(hid_dev, report, sizeof(report), NULL);
+	}
+
+	return -EINVAL;
+}
+
+void usb_hid_status_cb(enum usb_dc_status_code status, const u8_t *params)
+{
+	usb_status = status;
+};
+
+int zmk_usb_hid_init()
+{
+	int usb_enable_ret;
+
+	hid_dev = device_get_binding("HID_0");
+	if (hid_dev == NULL) {
+		LOG_ERR("Unable to locate HID device");
+		return -EINVAL;
+	}
+
+	usb_hid_register_device(hid_dev,
+	                        hid_report_desc, sizeof(hid_report_desc),
+	                        NULL);
+
+	usb_hid_init(hid_dev);
+
+	usb_enable_ret = usb_enable(usb_hid_status_cb);
+
+	if (usb_enable_ret != 0) {
+		LOG_ERR("Unable to enable USB");
+		return -EINVAL;
+	}
+
+	return 0;
+}