| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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. |
| */ |
| |
| /** |
| * @addtogroup OSKernel |
| * @{ |
| * @defgroup OSSem Semaphores |
| * @{ |
| */ |
| |
| #ifndef _OS_SEM_H_ |
| #define _OS_SEM_H_ |
| |
| #include "os/queue.h" |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif |
| |
| /** |
| * Structure representing an OS semaphore. |
| */ |
| struct os_sem { |
| SLIST_HEAD(, os_task) sem_head; |
| uint16_t _pad; |
| /** Number of tokens */ |
| uint16_t sem_tokens; |
| }; |
| |
| /* |
| XXX: NOTES |
| -> Should we add a magic number or flag to the semaphore structure so |
| that we know that this is a semaphore? We can use it for double checking |
| that a proper semaphore was passed in to the API. |
| -> What debug information should we add to this structure? Who last |
| acquired the semaphore? File/line where it was released? |
| -> Should we add a name to the semaphore? |
| -> Should we add a "os_sem_inspect() api, like ucos? |
| */ |
| |
| /** |
| * Initialize a semaphore |
| * |
| * @param sem Pointer to semaphore |
| * tokens: # of tokens the semaphore should contain initially. |
| * |
| * @return os_error_t |
| * OS_INVALID_PARM Semaphore passed in was NULL. |
| * OS_OK no error. |
| */ |
| os_error_t os_sem_init(struct os_sem *sem, uint16_t tokens); |
| |
| /** |
| * Release a semaphore. |
| * |
| * @param sem Pointer to the semaphore to be released |
| * |
| * @return os_error_t |
| * OS_INVALID_PARM Semaphore passed in was NULL. |
| * OS_OK No error |
| */ |
| os_error_t os_sem_release(struct os_sem *sem); |
| |
| /** |
| * os sem pend |
| * |
| * Pend (wait) for a semaphore. |
| * |
| * @param mu Pointer to semaphore. |
| * @param timeout Timeout, in os ticks. |
| * A timeout of 0 means do not wait if not available. |
| * A timeout of OS_TIMEOUT_NEVER means wait forever. |
| * |
| * |
| * @return os_error_t |
| * OS_INVALID_PARM Semaphore passed in was NULL. |
| * OS_TIMEOUT Semaphore was owned by another task and timeout=0 |
| * OS_OK no error. |
| */ |
| os_error_t os_sem_pend(struct os_sem *sem, os_time_t timeout); |
| |
| /** |
| * Get current semaphore's count |
| */ |
| static inline uint16_t os_sem_get_count(struct os_sem *sem) |
| { |
| return sem->sem_tokens; |
| } |
| |
| #ifdef __cplusplus |
| } |
| #endif |
| |
| #endif /* _OS_SEM_H_ */ |
| |
| |
| /** |
| * @} OSSem |
| * @} OSKernel |
| */ |