[nrf52] Read keyboard LED reports

Because on nRF52 all of our USB interfaces have OUT endpoints, we are
not getting CapsLock etc. LED states through set_report_cb(). Instead
we have to register an int_out_ready callback and read them from
there.

We still don't forward LED states to the devices connected over
Bluetooth, but it should now be possible to use LED states as inputs,
for layers etc., same as on the RP2040 version.

firmware-bluetooth/src/main.cc

@@ -54,7 +54,7 @@ static const struct device* hid_dev0;
 static const struct device* hid_dev1;  // config interface
 
 struct report_type {
-    uint8_t conn_idx;
+    uint16_t interface;
     uint8_t len;
     uint8_t data[65];
 };
@@ -503,7 +503,7 @@ static uint8_t hogp_notify_cb(struct bt_hogp* hogp, struct bt_hogp_rep_info* rep
     }
 
     static struct report_type buf;
-    buf.conn_idx = hogp_index(hogp);
+    buf.interface = hogp_index(hogp) << 8;
     buf.len = bt_hogp_rep_size(rep) + 1;
     buf.data[0] = bt_hogp_rep_id(rep);
 
@@ -676,6 +676,16 @@ static void int_in_ready_cb0(const struct device* dev) {
     k_sem_give(&usb_sem0);
 }
 
+static void int_out_ready_cb0(const struct device* dev) {
+    static struct report_type buf;
+    uint32_t len;
+    if (CHK(hid_int_ep_read(hid_dev0, buf.data, sizeof(buf.data), &len))) {
+        buf.interface = OUR_OUT_INTERFACE;
+        buf.len = len;
+        CHK(k_msgq_put(&report_q, &buf, K_NO_WAIT));
+    }
+}
+
 static void int_in_ready_cb1(const struct device* dev) {
     k_sem_give(&usb_sem1);
 }
@@ -684,6 +694,7 @@ static const struct hid_ops ops0 = {
     .get_report = get_report_cb,
     .set_report = set_report_cb,
     .int_in_ready = int_in_ready_cb0,
+    .int_out_ready = int_out_ready_cb0,
 };
 
 static const struct hid_ops ops1 = {
@@ -912,7 +923,7 @@ int main() {
 
     while (true) {
         if (!process_pending && !k_msgq_get(&report_q, &incoming_report, K_NO_WAIT)) {
-            handle_received_report(incoming_report.data, incoming_report.len, (uint16_t) incoming_report.conn_idx << 8);
+            handle_received_report(incoming_report.data, incoming_report.len, (uint16_t) incoming_report.interface);
             process_pending = true;
         }
         if (atomic_test_and_clear_bit(tick_pending, 0)) {