stm32/usb: Use a table of allowed values to simplify usb_mode get/set.

This reduces code size and code duplication, and fixes `pyb.usb_mode()` so
that it now returns the correct string when in multi-VCP mode (before, it
would return None when in one of these modes).

Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/qstrdefsport.h

@@ -38,7 +38,19 @@ Q(/)
 
 #if MICROPY_HW_ENABLE_USB
 // for usb modes
-Q(MSC+HID)
+Q(VCP)
+Q(MSC)
 Q(VCP+MSC)
 Q(VCP+HID)
+Q(VCP+MSC+HID)
+#if MICROPY_HW_USB_CDC_NUM >= 2
+Q(2xVCP)
+Q(2xVCP+MSC)
+Q(2xVCP+MSC+HID)
+#endif
+#if MICROPY_HW_USB_CDC_NUM >= 3
+Q(3xVCP)
+Q(3xVCP+MSC)
+Q(3xVCP+MSC+HID)
+#endif
 #endif

ports/stm32/usb.c

@@ -396,6 +396,35 @@ usbd_cdc_itf_t *usb_vcp_get(int idx) {
     pyb.usb_mode(..., port=2) # for second USB port
 */
 
+typedef struct _pyb_usb_mode_table_t {
+    uint8_t usbd_mode;
+    uint16_t qst;
+    const char *deprecated_str;
+    uint16_t default_pid;
+} pyb_usb_mode_table_t;
+
+// These are all the modes supported by USBD_SelectMode.
+// Note: there are some names (eg CDC, VCP+VCP) which are supported for backwards compatibility.
+STATIC const pyb_usb_mode_table_t pyb_usb_mode_table[] = {
+    { USBD_MODE_CDC, MP_QSTR_VCP, "CDC", MICROPY_HW_USB_PID_CDC },
+    { USBD_MODE_MSC, MP_QSTR_MSC, NULL, MICROPY_HW_USB_PID_MSC },
+    { USBD_MODE_CDC_MSC, MP_QSTR_VCP_plus_MSC, "CDC+MSC", MICROPY_HW_USB_PID_CDC_MSC },
+    { USBD_MODE_CDC_HID, MP_QSTR_VCP_plus_HID, "CDC+HID", MICROPY_HW_USB_PID_CDC_HID },
+    { USBD_MODE_CDC_MSC_HID, MP_QSTR_VCP_plus_MSC_plus_HID, NULL, MICROPY_HW_USB_PID_CDC_MSC_HID },
+
+    #if MICROPY_HW_USB_CDC_NUM >= 2
+    { USBD_MODE_CDC2, MP_QSTR_2xVCP, "VCP+VCP", MICROPY_HW_USB_PID_CDC2 },
+    { USBD_MODE_CDC2_MSC, MP_QSTR_2xVCP_plus_MSC, "VCP+VCP+MSC", MICROPY_HW_USB_PID_CDC2_MSC },
+    { USBD_MODE_CDC2_MSC_HID, MP_QSTR_2xVCP_plus_MSC_plus_HID, NULL, MICROPY_HW_USB_PID_CDC2_MSC_HID },
+    #endif
+
+    #if MICROPY_HW_USB_CDC_NUM >= 3
+    { USBD_MODE_CDC3, MP_QSTR_3xVCP, NULL, MICROPY_HW_USB_PID_CDC3 },
+    { USBD_MODE_CDC3_MSC, MP_QSTR_3xVCP_plus_MSC, NULL, MICROPY_HW_USB_PID_CDC3_MSC },
+    { USBD_MODE_CDC3_MSC_HID, MP_QSTR_3xVCP_plus_MSC_plus_HID, NULL, MICROPY_HW_USB_PID_CDC3_MSC_HID },
+    #endif
+};
+
 STATIC mp_obj_t pyb_usb_mode(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum {
         ARG_mode, ARG_port, ARG_vid, ARG_pid,
@@ -430,23 +459,14 @@ STATIC mp_obj_t pyb_usb_mode(size_t n_args, const mp_obj_t *pos_args, mp_map_t *
         #if defined(USE_HOST_MODE)
         return MP_OBJ_NEW_QSTR(MP_QSTR_host);
         #else
-        uint8_t mode = USBD_GetMode(&usb_device.usbd_cdc_msc_hid_state);
+        uint8_t mode = USBD_GetMode(&usb_device.usbd_cdc_msc_hid_state) & USBD_MODE_IFACE_MASK;
-        switch (mode & USBD_MODE_IFACE_MASK) {
+        for (size_t i = 0; i < MP_ARRAY_SIZE(pyb_usb_mode_table); ++i) {
-            case USBD_MODE_CDC:
+            const pyb_usb_mode_table_t *m = &pyb_usb_mode_table[i];
-                return MP_OBJ_NEW_QSTR(MP_QSTR_VCP);
+            if (mode == m->usbd_mode) {
-            case USBD_MODE_MSC:
+                return MP_OBJ_NEW_QSTR(m->qst);
-                return MP_OBJ_NEW_QSTR(MP_QSTR_MSC);
+            }
-            case USBD_MODE_HID:
-                return MP_OBJ_NEW_QSTR(MP_QSTR_HID);
-            case USBD_MODE_CDC_MSC:
-                return MP_OBJ_NEW_QSTR(MP_QSTR_VCP_plus_MSC);
-            case USBD_MODE_CDC_HID:
-                return MP_OBJ_NEW_QSTR(MP_QSTR_VCP_plus_HID);
-            case USBD_MODE_MSC_HID:
-                return MP_OBJ_NEW_QSTR(MP_QSTR_MSC_plus_HID);
-            default:
-                return mp_const_none;
         }
+        return mp_const_none;
         #endif
     }
 
@@ -483,70 +503,21 @@ STATIC mp_obj_t pyb_usb_mode(size_t n_args, const mp_obj_t *pos_args, mp_map_t *
 
     // get the VID, PID and USB mode
     // note: PID=-1 means select PID based on mode
-    // note: we support CDC as a synonym for VCP for backward compatibility
     uint16_t vid = args[ARG_vid].u_int;
     mp_int_t pid = args[ARG_pid].u_int;
-    uint8_t mode;
+    uint8_t mode = 0;
-    if (strcmp(mode_str, "CDC+MSC") == 0 || strcmp(mode_str, "VCP+MSC") == 0) {
+    for (size_t i = 0; i < MP_ARRAY_SIZE(pyb_usb_mode_table); ++i) {
-        if (pid == -1) {
+        const pyb_usb_mode_table_t *m = &pyb_usb_mode_table[i];
-            pid = MICROPY_HW_USB_PID_CDC_MSC;
+        if (strcmp(mode_str, qstr_str(m->qst)) == 0
-        }
+            || (m->deprecated_str != NULL && strcmp(mode_str, m->deprecated_str) == 0)) {
-        mode = USBD_MODE_CDC_MSC;
+            if (pid == -1) {
-    } else if (strcmp(mode_str, "VCP+MSC+HID") == 0) {
+                pid = m->default_pid;
-        if (pid == -1) {
+            }
-            pid = MICROPY_HW_USB_PID_CDC_MSC_HID;
+            mode = m->usbd_mode;
-        }
+            break;
-        mode = USBD_MODE_CDC_MSC_HID;
-    #if MICROPY_HW_USB_CDC_NUM >= 2
-    } else if (strcmp(mode_str, "VCP+VCP") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_CDC2;
-        }
-        mode = USBD_MODE_CDC2;
-    } else if (strcmp(mode_str, "VCP+VCP+MSC") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_CDC2_MSC;
-        }
-        mode = USBD_MODE_CDC2_MSC;
-    } else if (strcmp(mode_str, "2xVCP+MSC+HID") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_CDC2_MSC_HID;
-        }
-        mode = USBD_MODE_CDC2_MSC_HID;
-    #endif
-    #if MICROPY_HW_USB_CDC_NUM >= 3
-    } else if (strcmp(mode_str, "3xVCP") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_CDC3;
-        }
-        mode = USBD_MODE_CDC3;
-    } else if (strcmp(mode_str, "3xVCP+MSC") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_CDC3_MSC;
-        }
-        mode = USBD_MODE_CDC3_MSC;
-    } else if (strcmp(mode_str, "3xVCP+MSC+HID") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_CDC3_MSC_HID;
-        }
-        mode = USBD_MODE_CDC3_MSC_HID;
-    #endif
-    } else if (strcmp(mode_str, "CDC+HID") == 0 || strcmp(mode_str, "VCP+HID") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_CDC_HID;
-        }
-        mode = USBD_MODE_CDC_HID;
-    } else if (strcmp(mode_str, "CDC") == 0 || strcmp(mode_str, "VCP") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_CDC;
-        }
-        mode = USBD_MODE_CDC;
-    } else if (strcmp(mode_str, "MSC") == 0) {
-        if (pid == -1) {
-            pid = MICROPY_HW_USB_PID_MSC;
         }
-        mode = USBD_MODE_MSC;
+    }
-    } else {
+    if (mode == 0) {
         goto bad_mode;
     }