Add USB utility classes

Add an allocation free linked list implementation. Additionally add
the class AsyncOp which provides blocking and wakeup funcionality
to simplify making asynchronous operations block.

usb/device/utilities/AsyncOp.cpp

@@ -0,0 +1,84 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018-2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "AsyncOp.h"
+#include "mbed_critical.h"
+
+using namespace rtos;
+
+AsyncOp::AsyncOp(Mutex *lock): _list(NULL), _signal(NULL), _signal_lock(lock)
+{
+
+}
+
+void AsyncOp::start(LinkedListBase *list)
+{
+    _lock();
+    _list = list;
+    list->enqueue(this);
+    _unlock();
+}
+
+void AsyncOp::wait()
+{
+    if (_list == NULL) {
+        // Event either hasn't start or has already occurred
+        return;
+    }
+
+    // Construct semaphore to wait on
+    Semaphore sem(0);
+
+    // Atomically set the semaphore pointer and
+    // check for completion
+    _lock();
+    bool done = _list == NULL;
+    _signal = &sem;
+    _unlock();
+
+    if (!done) {
+        sem.wait();
+    }
+}
+
+void AsyncOp::complete()
+{
+    _lock();
+    _list->remove(this);
+    _list = NULL;
+    if (_signal != NULL) {
+        _signal->release();
+    }
+    _unlock();
+}
+
+void AsyncOp::_lock()
+{
+    if (_signal_lock) {
+        _signal_lock->lock();
+    } else {
+        core_util_critical_section_enter();
+    }
+}
+
+void AsyncOp::_unlock()
+{
+    if (_signal_lock) {
+        _signal_lock->unlock();
+    } else {
+        core_util_critical_section_exit();
+    }
+}

usb/device/utilities/AsyncOp.h

@@ -0,0 +1,62 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018-2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MBED_ASYNC_OP_H
+#define MBED_ASYNC_OP_H
+
+#include "Mutex.h"
+#include "Semaphore.h"
+
+#include "LinkEntry.h"
+#include "LinkedListBase.h"
+
+class AsyncOp: public LinkEntry {
+public:
+    /**
+     * Construct a new AsyncOp object
+     *
+     * @param lock Mutex used to serialize the object or code calling complete
+     *  or NULL if a critical section is used
+     */
+    AsyncOp(rtos::Mutex *lock);
+
+    /**
+     * Add this operation to the linked list to start it
+     */
+    void start(LinkedListBase *list);
+
+    /**
+     * Wait for this asynchronous operation to complete
+     */
+    void wait();
+
+    /**
+     * Mark this asynchronous operation as complete
+     *
+     * This wake the thread calling wait()
+     */
+    void complete();
+
+private:
+    void _lock();
+    void _unlock();
+
+    LinkedListBase *_list;
+    rtos::Semaphore *_signal;
+    rtos::Mutex *const _signal_lock;
+};
+
+#endif

usb/device/utilities/LinkEntry.h

@@ -0,0 +1,35 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018-2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MBED_LINKED_ENTRY_H
+#define MBED_LINKED_ENTRY_H
+
+#include <cstddef>
+
+class LinkEntry {
+public:
+    LinkEntry(): _next(NULL)
+    {
+
+    }
+
+private:
+    friend class LinkedListBase;
+    LinkEntry *_next;
+};
+
+
+#endif

usb/device/utilities/LinkedList.h

@@ -0,0 +1,60 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018-2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MBED_LINKED_LIST_H
+#define MBED_LINKED_LIST_H
+
+#include "LinkEntry.h"
+#include "LinkedListBase.h"
+
+template<class T>
+class LinkedList: public LinkedListBase {
+public:
+    LinkedList() {}
+    ~LinkedList() {}
+
+    /**
+     * Return the element at the head of the list
+     *
+     * @return The element at the head of the list or NULL if the list is empty
+     */
+    T *head()
+    {
+        return static_cast<T *>(LinkedListBase::head());
+    }
+
+    /**
+     * Add an element to the tail of the list
+     *
+     * @param entry New element to add
+     */
+    void enqueue(T *entry)
+    {
+        LinkedListBase::enqueue(static_cast<LinkEntry *>(entry));
+    }
+
+    /**
+     * Remove the element at the head of the list
+     *
+     * @return The element at the head of the list or NULL if the list is empty
+     */
+    T *dequeue()
+    {
+        return static_cast<T *>(LinkedListBase::dequeue());
+    }
+};
+
+#endif

usb/device/utilities/LinkedListBase.cpp

@@ -0,0 +1,84 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018-2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "LinkedList.h"
+#include "LinkEntry.h"
+#include "mbed_assert.h"
+
+LinkedListBase::LinkedListBase(): _head(0), _tail(0)
+{
+
+}
+
+LinkedListBase::~LinkedListBase()
+{
+
+}
+
+LinkEntry *LinkedListBase::head()
+{
+    return _head;
+}
+
+void LinkedListBase::enqueue(LinkEntry *entry)
+{
+    entry->_next = NULL;
+    if (_tail == NULL) {
+        _head = entry;
+    } else {
+        _tail->_next = entry;
+    }
+    _tail = entry;
+}
+
+LinkEntry *LinkedListBase::dequeue()
+{
+    if (_head == NULL) {
+        return NULL;
+    }
+    if (_head->_next == NULL) {
+        _tail = NULL;
+    }
+    LinkEntry *entry = _head;
+    _head = _head->_next;
+    entry->_next = NULL;
+    return entry;
+}
+
+void LinkedListBase::remove(LinkEntry *entry)
+{
+    LinkEntry *prev = NULL;
+    LinkEntry *cur = _head;
+    while (cur != entry) {
+        if (cur == NULL) {
+            // Element is not in the list
+            return;
+        }
+        prev = cur;
+        cur = cur->_next;
+    }
+
+    if (prev != NULL) {
+        prev->_next = entry->_next;
+    }
+    if (entry == _head) {
+        _head = entry->_next;
+    }
+    if (entry == _tail) {
+        _tail = prev;
+    }
+    entry->_next = NULL;
+}

usb/device/utilities/LinkedListBase.h

@@ -0,0 +1,60 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018-2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MBED_LINKED_LIST_BASE_H
+#define MBED_LINKED_LIST_BASE_H
+
+#include "LinkEntry.h"
+
+class LinkedListBase {
+public:
+    LinkedListBase();
+    ~LinkedListBase();
+
+    /**
+     * Return the element at the head of the list
+     *
+     * @return The element at the head of the list or NULL if the list is empty
+     */
+    LinkEntry *head();
+
+    /**
+     * Add an element to the tail of the list
+     *
+     * @param entry New element to add
+     */
+    void enqueue(LinkEntry *entry);
+
+    /**
+     * Remove the element at the head of the list
+     *
+     * @return The element at the head of the list or NULL if the list is empty
+     */
+    LinkEntry *dequeue();
+
+    /**
+     * Remove the specified element if it is in the list
+     *
+     * @param entry Element to remove from the list
+     */
+    void remove(LinkEntry *entry);
+
+private:
+    LinkEntry *_head;
+    LinkEntry *_tail;
+};
+
+#endif