wifi: allow 5 GHz channels in start_ap()

ports/espressif/common-hal/wifi/Radio.c

@@ -242,6 +242,7 @@ void common_hal_wifi_radio_stop_station(wifi_radio_obj_t *self) {
 }
 
 void common_hal_wifi_radio_start_ap(wifi_radio_obj_t *self, uint8_t *ssid, size_t ssid_len, uint8_t *password, size_t password_len, uint8_t channel, uint32_t authmode, uint8_t max_connections) {
+    bool was_ap = self->ap_mode;
     set_mode_ap(self, true);
 
     uint8_t esp_authmode = 0;
@@ -275,7 +276,18 @@ void common_hal_wifi_radio_start_ap(wifi_radio_obj_t *self, uint8_t *ssid, size_
 
     config->ap.max_connection = max_connections;
 
-    esp_wifi_set_config(WIFI_IF_AP, config);
+    esp_err_t result = esp_wifi_set_config(WIFI_IF_AP, config);
+    if (result != ESP_OK) {
+        if (!was_ap) {
+            set_mode_ap(self, false);
+        }
+        // The IDF returns ESP_ERR_INVALID_ARG for a channel this radio or its
+        // country setting cannot use (wifi_ap_config_t.channel).
+        if (result == ESP_ERR_INVALID_ARG) {
+            mp_arg_error_invalid(MP_QSTR_channel);
+        }
+        raise_esp_error(result);
+    }
     // Wait a few ms for the AP to start. Empirically, this takes < 3ms on ESP32, and < 1ms on other chips.
     for (size_t ms = 0; ms < 10; ms++) {
         if (common_hal_wifi_radio_get_ap_active(self)) {

ports/raspberrypi/common-hal/wifi/Radio.c

@@ -196,6 +196,9 @@ void common_hal_wifi_radio_start_ap(wifi_radio_obj_t *self, uint8_t *ssid, size_
         mp_raise_RuntimeError(MP_ERROR_TEXT("WiFi is not enabled"));
     }
 
+    // The CYW43 is 2.4 GHz only.
+    mp_arg_validate_int_max(channel, 13, MP_QSTR_channel);
+
     /* TODO: If the AP is stopped once it cannot be restarted.
      * This means that if if the user does:
      *

shared-bindings/wifi/Radio.c

@@ -342,6 +342,8 @@ MP_DEFINE_CONST_FUN_OBJ_1(wifi_radio_stop_station_obj, wifi_radio_stop_station);
 //|
 //|         If ``channel`` is given, the access point will use that channel unless
 //|         a station is already operating on a different channel.
+//|         On dual-band radios, 5 GHz channels (36 and above) may also be given.
+//|         A channel the radio does not support raises `ValueError`.
 //|
 //|         If ``authmode`` is not None, the access point will use the given authentication modes.
 //|         If a non-empty password is given, ``authmode`` must not include ``OPEN``.
@@ -363,7 +365,8 @@ MP_DEFINE_CONST_FUN_OBJ_1(wifi_radio_stop_station_obj, wifi_radio_stop_station);
 //|
 //|         .. note::
 //|
-//|             In the raspberrypi port (RP2040 CYW43), ``max_connections`` is ignored.
+//|             In the raspberrypi port (RP2040 CYW43), ``max_connections`` is ignored
+//|             and only 2.4 GHz channels (1-13) are accepted.
 //|         """
 //|         ...
 //|
@@ -403,7 +406,9 @@ static mp_obj_t wifi_radio_start_ap(size_t n_args, const mp_obj_t *pos_args, mp_
         }
     }
 
-    mp_int_t channel = mp_arg_validate_int_range(args[ARG_channel].u_int, 1, 13, MP_QSTR_channel);
+    // 165 is the highest channel in the scan pattern. Channels the radio
+    // doesn't support are rejected by the port rather than here.
+    mp_int_t channel = mp_arg_validate_int_range(args[ARG_channel].u_int, 1, 165, MP_QSTR_channel);
 
     if (authmode == AUTHMODE_OPEN && password.len > 0) {
         mp_raise_ValueError(MP_ERROR_TEXT("AuthMode.OPEN is not used with password"));