BREAKING: Support dynamic USB reconfiguration

Now that the USB descriptor and HID reports are handled by code, it is
possible to change then on-the-fly from an application and customize
the USB vendor/product/etc.

It is also possible to add and remove HID and other devices, at runtime.

Serial (USB) now properly handles `Serial.end()` and completely removes
the USB CDC descriptor for the Serial port when called.  That makes
it possible to build sketches which only export HID (Keyboard, Joystick,
Mouse) or MSC (FatFSUSB or SingleFileDrive) devices and no Serial
port.

All USB devices now register themselves on `xxx.begin()` and not
at the start of the sketch.  This could be breaking for sketches
which (incorrectly) forget to call `Keyboard.begin()` before running,
for example.  In most cases this will be a non-issue because most
scripts (all examples here!) so call begin() as appropriate.

Updates the documentation with the new USB calls for end users.
Advanced users can check out the shipped libraries for more
complicated customization (adding/removing custom devices).

Author: earlephilhower

cores/rp2040/Arduino.h

@@ -25,6 +25,7 @@
 #include <string.h>
 #include "stdlib_noniso.h" // Wacky deprecated AVR compatibility functions
 #include "RP2040Version.h"
+#include "RP2040USB.h"
 #include "api/ArduinoAPI.h"
 #include "api/itoa.h" // ARM toolchain doesn't provide itoa etc, provide them
 #include <pico.h>

cores/rp2040/RP2040USB.cpp

@@ -79,25 +79,59 @@ static uint8_t usbd_desc_str_cnt = 0;
 static uint8_t usbd_desc_str_alloc = 0;
 
 // HID report
+static unsigned int __hid_interface = (unsigned int)-1;
+static uint8_t __hid_endpoint = 0;
 static int      __hid_report_len = 0;
 static uint8_t *__hid_report     = nullptr;
 
 // Global USB descriptor
 static uint8_t *usbd_desc_cfg = nullptr;
+static int usbd_desc_cfg_len = 0;
+
 #ifdef ENABLE_PICOTOOL_USB
 static uint8_t _picotool_itf_num;
 #endif
 int usb_hid_poll_interval __attribute__((weak)) = 10;
 
 
+// Available bitmask for endpoints, can never be EP 0
+static uint32_t _endpointIn = 0xfffffffe;
+static uint32_t _endpointOut = 0xfffffffe;
+
+// GCC doesn't seem to have builtin_ffs here
+static int ffs(uint32_t v) {
+    for (auto i = 0; i < 32; i++) {
+        if (v & (1<<i)) {
+            return i;
+        }
+    }
+    return 0;
+}
+
 uint8_t usbRegisterEndpointIn() {
-    static uint8_t epin = 0x81;
-    return epin++;
+    if (!_endpointIn) {
+        return 0; // ERROR, out of EPs
+    }
+    int firstFree = ffs(_endpointIn);
+    _endpointIn &= ~(1 << firstFree);
+    return 0x80 + firstFree;
+}
+
+void usbUnregisterEndpointIn(int ep) {
+    _endpointIn |= 1 << ep;
 }
 
 uint8_t usbRegisterEndpointOut() {
-    static uint8_t epout = 0x01;
-    return epout++;
+    if (!_endpointOut) {
+        return 0; // ERROR, out of EPs
+    }
+    int firstFree = ffs(_endpointOut);
+    _endpointOut &= ~(1 << firstFree);
+    return firstFree;
+}
+
+void usbUnregisterEndpointOut(int ep) {
+    _endpointOut |= (1 << (ep - 0x80));
 }
 
 static uint8_t AddEntry(Entry **head, int interfaces, const uint8_t *descriptor, size_t len, int ordering, uint32_t vidMask) {
@@ -132,6 +166,27 @@ static uint8_t AddEntry(Entry **head, int interfaces, const uint8_t *descriptor,
     return n->localid;
 }
 
+static void RemoveEntry(Entry **head, unsigned int localid) {
+    Entry *prev = nullptr;
+    Entry *cur = *head;
+    while (cur && cur->localid != localid) {
+        prev = cur;
+        cur = cur->next;
+    }
+    if (!cur) {
+        // Not found, just exit
+        return;
+    }
+    if (cur == *head) {
+        auto p = cur->next;
+        free(*head);
+        *head = p;
+    } else {
+        prev->next = cur->next;
+        free(cur);
+    }
+}
+
 // Find the index (HID report ID or USB interface) of a given localid
 static unsigned int usbFindID(Entry *head, unsigned int localid) {
     unsigned int x = 0;
@@ -156,11 +211,18 @@ uint8_t usbRegisterHIDDevice(const uint8_t *descriptor, size_t len, int ordering
     return AddEntry(&_hids, 0, descriptor, len, ordering, vidMask);
 }
 
+void usbUnregisterHIDDevice(unsigned int localid) {
+    RemoveEntry(&_hids, localid);
+}
+
 // Called by an object at global init time to add a new interface (non-HID, like CDC or Picotool)
 uint8_t usbRegisterInterface(int interfaces, const uint8_t *descriptor, size_t len, int ordering, uint32_t vidMask) {
     return AddEntry(&_interfaces, interfaces, descriptor, len, ordering, vidMask);
 }
 
+void usbUnregisterInterface(unsigned int localid) {
+    RemoveEntry(&_interfaces, localid);
+}
 
 uint8_t usbRegisterString(const char *str) {
     if (usbd_desc_str_alloc <= usbd_desc_str_cnt) {
@@ -182,41 +244,62 @@ uint8_t usbRegisterString(const char *str) {
     return usbd_desc_str_cnt++;
 }
 
+static uint16_t _forceVID = 0;
+static uint16_t _forcePID = 0;
+void usbSetVIDPID(uint16_t vid, uint16_t pid) {
+    _forceVID = vid;
+    _forcePID = pid;
+}
 
+static uint8_t _forceManuf = 0;
+static uint8_t _forceProd = 0;
+static uint8_t _forceSerial = 0;
+void usbSetManufacturer(const char *str) {
+    _forceManuf = usbRegisterString(str);
+}
+void usbSetProduct(const char *str) {
+    _forceProd = usbRegisterString(str);
+}
+void usbSetSerialNumber(const char *str) {
+    _forceSerial = usbRegisterString(str);
+}
 
+static tusb_desc_device_t usbd_desc_device;
 const uint8_t *tud_descriptor_device_cb(void) {
     static char idString[PICO_UNIQUE_BOARD_ID_SIZE_BYTES * 3 + 1];
     if (!idString[0]) {
         pico_get_unique_board_id_string(idString, sizeof(idString));
     }
 
-    static tusb_desc_device_t usbd_desc_device = {
+    usbd_desc_device = {
         .bLength = sizeof(tusb_desc_device_t),
         .bDescriptorType = TUSB_DESC_DEVICE,
         .bcdUSB = 0x0200,
         .bDeviceClass = 0,
         .bDeviceSubClass = 0,
         .bDeviceProtocol = 0,
         .bMaxPacketSize0 = CFG_TUD_ENDPOINT0_SIZE,
-        .idVendor = USBD_VID,
-        .idProduct = USBD_PID,
+        .idVendor = _forceVID ? _forceVID : (uint16_t)USBD_VID,
+        .idProduct = _forcePID ? _forcePID : (uint16_t)USBD_PID,
         .bcdDevice = 0x0100,
-        .iManufacturer = usbRegisterString(USB_MANUFACTURER),
-        .iProduct = usbRegisterString(USB_PRODUCT),
-        .iSerialNumber = usbRegisterString(idString),
+        .iManufacturer = _forceManuf ? _forceManuf : usbRegisterString(USB_MANUFACTURER),
+        .iProduct = _forceProd ? _forceProd : usbRegisterString(USB_PRODUCT),
+        .iSerialNumber = _forceSerial ? _forceSerial : usbRegisterString(idString),
         .bNumConfigurations = 1
     };
 
-    // Handle any inversions from the sub-devices
-    Entry *h = _hids;
-    while (h) {
-        usbd_desc_device.idProduct ^= h->mask;
-        h = h->next;
-    }
-    h = _interfaces;
-    while (h) {
-        usbd_desc_device.idProduct ^= h->mask;
-        h = h->next;
+    // Handle any inversions from the sub-devices, if we're not forcing things
+    if (!_forcePID) {
+        Entry *h = _hids;
+        while (h) {
+            usbd_desc_device.idProduct ^= h->mask;
+            h = h->next;
+        }
+        h = _interfaces;
+        while (h) {
+            usbd_desc_device.idProduct ^= h->mask;
+            h = h->next;
+        }
     }
 
     return (const uint8_t *)&usbd_desc_device;
@@ -282,7 +365,6 @@ const uint8_t *tud_descriptor_configuration_cb(uint8_t index) {
 // needed ever again
 void __SetupUSBDescriptor() {
     uint8_t interface_count = 0;
-    int usbd_desc_len;
     if (usbd_desc_cfg) {
         return;
     }
@@ -291,32 +373,33 @@ void __SetupUSBDescriptor() {
     if (GetDescHIDReport(&hid_report_len)) {
         uint8_t hid_desc[TUD_HID_DESC_LEN] = {
             // Interface number, string index, protocol, report descriptor len, EP In & Out address, size & polling interval
-            TUD_HID_DESCRIPTOR(1 /* placeholder*/, 0, HID_ITF_PROTOCOL_NONE, hid_report_len, usbRegisterEndpointIn(), CFG_TUD_HID_EP_BUFSIZE, (uint8_t)usb_hid_poll_interval)
+            TUD_HID_DESCRIPTOR(1 /* placeholder*/, 0, HID_ITF_PROTOCOL_NONE, hid_report_len, __hid_endpoint = usbRegisterEndpointIn(), CFG_TUD_HID_EP_BUFSIZE, (uint8_t)usb_hid_poll_interval)
         };
-        usbRegisterInterface(1, hid_desc, sizeof(hid_desc), 10, 0);
+        __hid_interface = usbRegisterInterface(1, hid_desc, sizeof(hid_desc), 10, 0);
     }
 
 #ifdef ENABLE_PICOTOOL_USB
     uint8_t picotool_desc[] = { TUD_RPI_RESET_DESCRIPTOR(1, usbRegisterString("Reset")) };
     usbRegisterInterface(1, picotool_desc, sizeof(picotool_desc), 100, 0);
 #endif
 
-    usbd_desc_len = TUD_CONFIG_DESC_LEN; // Always have a config descriptor
+    usbd_desc_cfg_len = TUD_CONFIG_DESC_LEN; // Always have a config descriptor
     Entry *h = _interfaces;
     while (h) {
-        usbd_desc_len += h->len;
+        usbd_desc_cfg_len += h->len;
         interface_count += h->interfaces;
         h = h->next;
     }
 
     uint8_t tud_cfg_desc[TUD_CONFIG_DESC_LEN] = {
         // Config number, interface count, string index, total length, attribute, power in mA
-        TUD_CONFIG_DESCRIPTOR(1, interface_count, usbRegisterString(""), usbd_desc_len, TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, USBD_MAX_POWER_MA)
+        TUD_CONFIG_DESCRIPTOR(1, interface_count, usbRegisterString(""), usbd_desc_cfg_len, TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, USBD_MAX_POWER_MA)
     };
 
     // Allocate the "real" HID report descriptor
-    usbd_desc_cfg = (uint8_t *)malloc(usbd_desc_len);
+    usbd_desc_cfg = (uint8_t *)malloc(usbd_desc_cfg_len);
     assert(usbd_desc_cfg);
+    bzero(usbd_desc_cfg, usbd_desc_cfg_len);
 
     // Now copy the descriptors
     h = _interfaces;
@@ -374,6 +457,48 @@ static int64_t timer_task(__unused alarm_id_t id, __unused void *user_data) {
     return USB_TASK_INTERVAL;
 }
 
+void usbDisconnect() {
+#ifdef __FREERTOS
+    auto m = __get_freertos_mutex_for_ptr(&__usb_mutex);
+    xSemaphoreTake(m, portMAX_DELAY);
+    tud_disconnect();
+    vTaskDelay(500 / portTICK_PERIOD_MS);
+    xSemaphoreGive(m);
+#else
+    mutex_enter_blocking(&__usb_mutex);
+    tud_disconnect();
+    sleep_ms(500);
+    mutex_exit(&__usb_mutex);
+#endif
+    // Ensure when we reconnect we make the new descriptor
+    free(usbd_desc_cfg);
+    usbd_desc_cfg = nullptr;
+    usbd_desc_cfg_len = 0;
+    if (__hid_report) {
+        usbUnregisterInterface(__hid_interface);
+        usbUnregisterEndpointIn(__hid_endpoint);
+    }
+    free(__hid_report);
+    __hid_report = nullptr;
+    __hid_report_len = 0;
+}
+
+void usbConnect()  {
+    __SetupDescHIDReport();
+    __SetupUSBDescriptor();
+
+#ifdef __FREERTOS
+    auto m = __get_freertos_mutex_for_ptr(&__usb_mutex);
+    xSemaphoreTake(m, portMAX_DELAY);
+    tusb_connect();
+    xSemaphoreGive(m);
+#else
+    mutex_enter_blocking(&__usb_mutex);
+    tud_connect();
+    mutex_exit(&__usb_mutex);
+#endif
+}
+
 void __USBStart() __attribute__((weak));
 
 void __USBStart() {

cores/rp2040/RP2040USB.h

@@ -25,10 +25,16 @@
 // Called by an object at global init time to register a HID device, returns a localID to be mapped using findHIDReportID
 // vidMask is the bits in the VID that should be XOR'd when this device is present.
 // 0 means don't invert anything, OTW select a single bitmask 1<<n.
-uint8_t usbRegisterHIDDevice(const uint8_t *descriptor, size_t len, int ordering, uint32_t vidMask = 0);
+uint8_t usbRegisterHIDDevice(const uint8_t *descriptor, size_t len, int ordering, uint32_t vidMask);
+
+// Remove a HID device from the USB descriptor.  Only call after usbDisconnect or results could be unpredictable!
+void usbUnregisterHIDDevice(unsigned int localid);
 
 // Called by an object at global init time to add a new interface (non-HID, like CDC or Picotool)
-uint8_t usbRegisterInterface(int interfaces, const uint8_t *descriptor, size_t len, int ordering = INT_MAX, uint32_t vidMask = 0);
+uint8_t usbRegisterInterface(int interfaces, const uint8_t *descriptor, size_t len, int ordering, uint32_t vidMask);
+
+// Remove a USB interface from the USB descriptor.  Only call after usbDisconnect or results could be unpredictable!
+void usbUnregisterInterface(unsigned int localid);
 
 // Get the USB HID actual report ID from the localid
 uint8_t usbFindHIDReportID(unsigned int localid);
@@ -42,6 +48,20 @@ uint8_t usbRegisterString(const char *str);
 // Get an unassigned in/cmd or out endpoint number
 uint8_t usbRegisterEndpointIn();
 uint8_t usbRegisterEndpointOut();
+void usbUnregisterEndpointIn(int ep);
+void usbUnregisterEndpointOut(int ep);
+
+// Disconnects the USB connection to allow editing the HID/interface list
+void usbDisconnect();
+
+// Reconnects the USB connection to pick up the new descriptor
+void usbConnect();
+
+// Override the hardcoded USB VID:PID, product, manufacturer, and serials
+void usbSetVIDPID(uint16_t vid, uint16_t pid);
+void usbSetManufacturer(const char *str);
+void usbSetProduct(const char *str);
+void usbSetSerialNumber(const char *str);
 
 // Big, global USB mutex, shared with all USB devices to make sure we don't
 // have multiple cores updating the TUSB state in parallel

cores/rp2040/SerialUSB.cpp

@@ -41,13 +41,13 @@ extern mutex_t __usb_mutex;
 #define USBD_CDC_IN_OUT_MAX_SIZE (64)
 
 
-static const uint8_t cdc_desc[TUD_CDC_DESC_LEN] = {
-    // Interface number, string index, protocol, report descriptor len, EP In & Out address, size & polling interval
-    TUD_CDC_DESCRIPTOR(0 /* placeholder*/, usbRegisterString("Pico Serial"), usbRegisterEndpointIn(), USBD_CDC_CMD_MAX_SIZE, usbRegisterEndpointOut(), usbRegisterEndpointIn(), USBD_CDC_IN_OUT_MAX_SIZE)
-};
+//static const uint8_t cdc_desc[TUD_CDC_DESC_LEN] = {
+//    // Interface number, string index, protocol, report descriptor len, EP In & Out address, size & polling interval
+//    TUD_CDC_DESCRIPTOR(0 /* placeholder*/, usbRegisterString("Pico Serial"), usbRegisterEndpointIn(), USBD_CDC_CMD_MAX_SIZE, usbRegisterEndpointOut(), usbRegisterEndpointIn(), USBD_CDC_IN_OUT_MAX_SIZE)
+//};
 
 SerialUSB::SerialUSB() {
-    _id = usbRegisterInterface(2, cdc_desc, sizeof(cdc_desc), 1, 0);
+//    _id = usbRegisterInterface(2, cdc_desc, sizeof(cdc_desc), 1, 0);
 }
 
 
@@ -58,11 +58,28 @@ void SerialUSB::begin(unsigned long baud) {
         return;
     }
 
+    usbDisconnect();
+    static uint8_t cdc_desc[TUD_CDC_DESC_LEN] = {
+        // Interface number, string index, protocol, report descriptor len, EP In & Out address, size & polling interval
+        TUD_CDC_DESCRIPTOR(0 /* placeholder*/, usbRegisterString("Pico Serial"), _epIn = usbRegisterEndpointIn(), USBD_CDC_CMD_MAX_SIZE, _epOut = usbRegisterEndpointOut(), usbRegisterEndpointIn(), USBD_CDC_IN_OUT_MAX_SIZE)
+    };
+
+    _id = usbRegisterInterface(2, cdc_desc, sizeof(cdc_desc), 1, 0);
+
+    usbConnect();
     _running = true;
 }
 
 void SerialUSB::end() {
-    // TODO
+    if (_running) {
+        usbDisconnect();
+        usbUnregisterInterface(_id);
+        usbUnregisterEndpointIn(_epIn);
+        usbUnregisterEndpointOut(_epOut);
+        _running = false;
+        usbConnect();
+    }
+
 }
 
 int SerialUSB::peek() {

cores/rp2040/SerialUSB.h

@@ -57,6 +57,8 @@ class SerialUSB : public arduino::HardwareSerial {
     bool _running = false;
     bool _ignoreFlowControl = false;
     uint8_t _id;
+    uint8_t _epIn;
+    uint8_t _epOut;
 };
 
 extern SerialUSB Serial;