device/pipe: add nonblocking read/write and force write mode

The previous implementation will always blocks the reader/writer.
However, at least FinSh would expect the device to be nonblocking ---
read should return 0 when there is no data in it.

components/drivers/include/rtdevice.h

@@ -75,6 +75,20 @@ struct rt_ringbuffer
 
 /* pipe device */
 #define PIPE_DEVICE(device)          ((struct rt_pipe_device*)(device))
+enum rt_pipe_flag
+{
+    /* both read and write won't block */
+    RT_PIPE_FLAG_NONBLOCK_RDWR = 0x00,
+    /* read would block */
+    RT_PIPE_FLAG_BLOCK_RD = 0x01,
+    /* write would block */
+    RT_PIPE_FLAG_BLOCK_WR = 0x02,
+    /* write to this pipe will discard some data when the pipe is full.
+     * When this flag is set, RT_PIPE_FLAG_BLOCK_WR will be ignored since write
+     * operation will always be success. */
+    RT_PIPE_FLAG_FORCE_WR = 0x04,
+};
+
 struct rt_pipe_device
 {
     struct rt_device parent;
@@ -82,6 +96,8 @@ struct rt_pipe_device
     /* ring buffer in pipe device */
     struct rt_ringbuffer ringbuffer;
 
+    enum rt_pipe_flag flag;
+
     /* suspended list */
     rt_list_t suspended_read_list;
     rt_list_t suspended_write_list;
@@ -199,11 +215,12 @@ rt_inline rt_uint16_t rt_ringbuffer_data_len(struct rt_ringbuffer *rb)
  */
 rt_err_t rt_pipe_init(struct rt_pipe_device *pipe,
                       const char *name,
+                      enum rt_pipe_flag flag,
                       rt_uint8_t *buf,
                       rt_size_t size);
 rt_err_t rt_pipe_detach(struct rt_pipe_device *pipe);
 #ifdef RT_USING_HEAP
-rt_err_t rt_pipe_create(const char *name, rt_size_t size);
+rt_err_t rt_pipe_create(const char *name, enum rt_pipe_flag flag, rt_size_t size);
 void rt_pipe_destroy(struct rt_pipe_device *pipe);
 #endif
 

components/drivers/src/pipe.c

@@ -26,6 +26,26 @@
 #include <rtthread.h>
 #include <rtdevice.h>
 
+static void _rt_pipe_resume_writer(struct rt_pipe_device *pipe)
+{
+    if (!rt_list_isempty(&pipe->suspended_write_list))
+    {
+        rt_thread_t thread;
+
+        RT_ASSERT(pipe->flag & RT_PIPE_FLAG_BLOCK_WR);
+
+        /* get suspended thread */
+        thread = rt_list_entry(pipe->suspended_write_list.next,
+                struct rt_thread,
+                tlist);
+
+        /* resume the write thread */
+        rt_thread_resume(thread);
+
+        rt_schedule();
+    }
+}
+
 static rt_size_t rt_pipe_read(rt_device_t dev,
                               rt_off_t    pos,
                               void       *buffer,
@@ -39,13 +59,26 @@ static rt_size_t rt_pipe_read(rt_device_t dev,
     pipe = PIPE_DEVICE(dev);
     RT_ASSERT(pipe != RT_NULL);
 
+    if (!(pipe->flag & RT_PIPE_FLAG_BLOCK_RD))
+    {
+        level = rt_hw_interrupt_disable();
+        read_nbytes = rt_ringbuffer_get(&(pipe->ringbuffer), buffer, size);
+
+        /* if the ringbuffer is empty, there won't be any writer waiting */
+        if (read_nbytes)
+            _rt_pipe_resume_writer(pipe);
+
+        rt_hw_interrupt_enable(level);
+
+        return read_nbytes;
+    }
+
     thread = rt_thread_self();
 
     /* current context checking */
     RT_DEBUG_NOT_IN_INTERRUPT;
 
-    do 
-    {
+    do {
         level = rt_hw_interrupt_disable();
         read_nbytes = rt_ringbuffer_get(&(pipe->ringbuffer), buffer, size);
         if (read_nbytes == 0)
@@ -60,23 +93,8 @@ static rt_size_t rt_pipe_read(rt_device_t dev,
         }
         else
         {
-            if (!rt_list_isempty(&pipe->suspended_write_list))
-            {
-                /* get suspended thread */
-                thread = rt_list_entry(pipe->suspended_write_list.next,
-                                       struct rt_thread,
-                                       tlist);
-
-                /* resume the write thread */
-                rt_thread_resume(thread);
-                rt_hw_interrupt_enable(level);
-
-                rt_schedule();
-            }
-            else
-            {
-                rt_hw_interrupt_enable(level);
-            }
+            _rt_pipe_resume_writer(pipe);
+            rt_hw_interrupt_enable(level);
             break;
         }
     } while (read_nbytes == 0);
@@ -84,6 +102,26 @@ static rt_size_t rt_pipe_read(rt_device_t dev,
     return read_nbytes;
 }
 
+static void _rt_pipe_resume_reader(struct rt_pipe_device *pipe)
+{
+    if (!rt_list_isempty(&pipe->suspended_read_list))
+    {
+        rt_thread_t thread;
+
+        RT_ASSERT(pipe->flag & RT_PIPE_FLAG_BLOCK_RD);
+
+        /* get suspended thread */
+        thread = rt_list_entry(pipe->suspended_read_list.next,
+                struct rt_thread,
+                tlist);
+
+        /* resume the read thread */
+        rt_thread_resume(thread);
+
+        rt_schedule();
+    }
+}
+
 struct rt_pipe_device *_pipe = RT_NULL;
 static rt_size_t rt_pipe_write(rt_device_t dev,
                                rt_off_t    pos,
@@ -100,13 +138,31 @@ static rt_size_t rt_pipe_write(rt_device_t dev,
     if (_pipe == RT_NULL)
         _pipe = pipe;
 
+    if ((pipe->flag & RT_PIPE_FLAG_FORCE_WR) ||
+       !(pipe->flag & RT_PIPE_FLAG_BLOCK_WR))
+    {
+        level = rt_hw_interrupt_disable();
+
+        if (pipe->flag & RT_PIPE_FLAG_FORCE_WR)
+            write_nbytes = rt_ringbuffer_put_force(&(pipe->ringbuffer),
+                                                   buffer, size);
+        else
+            write_nbytes = rt_ringbuffer_put(&(pipe->ringbuffer),
+                                             buffer, size);
+
+        _rt_pipe_resume_reader(pipe);
+
+        rt_hw_interrupt_enable(level);
+
+        return write_nbytes;
+    }
+
     thread = rt_thread_self();
 
     /* current context checking */
     RT_DEBUG_NOT_IN_INTERRUPT;
 
-    do
-    {
+    do {
         level = rt_hw_interrupt_disable();
         write_nbytes = rt_ringbuffer_put(&(pipe->ringbuffer), buffer, size);
         if (write_nbytes == 0)
@@ -122,26 +178,11 @@ static rt_size_t rt_pipe_write(rt_device_t dev,
         }
         else
         {
-            if (!rt_list_isempty(&pipe->suspended_read_list))
-            {
-                /* get suspended thread */
-                thread = rt_list_entry(pipe->suspended_read_list.next,
-                                       struct rt_thread,
-                                       tlist);
-
-                /* resume the read thread */
-                rt_thread_resume(thread);
-                rt_hw_interrupt_enable(level);
-
-                rt_schedule();
-            }
-            else
-            {
-                rt_hw_interrupt_enable(level);
-            }
+            _rt_pipe_resume_reader(pipe);
+            rt_hw_interrupt_enable(level);
             break;
         }
-    }while (write_nbytes == 0);
+    } while (write_nbytes == 0);
 
     return write_nbytes;
 }
@@ -157,6 +198,7 @@ static rt_err_t rt_pipe_control(rt_device_t dev, rt_uint8_t cmd, void *args)
  *
  * @param pipe the pipe device
  * @param name the name of pipe device
+ * @param flag the attribute of the pipe device
  * @param buf  the buffer of pipe device
  * @param size the size of pipe device buffer
  *
@@ -164,6 +206,7 @@ static rt_err_t rt_pipe_control(rt_device_t dev, rt_uint8_t cmd, void *args)
  */
 rt_err_t rt_pipe_init(struct rt_pipe_device *pipe,
                       const char *name,
+                      enum rt_pipe_flag flag,
                       rt_uint8_t *buf,
                       rt_size_t size)
 {
@@ -177,6 +220,8 @@ rt_err_t rt_pipe_init(struct rt_pipe_device *pipe,
     /* initialize ring buffer */
     rt_ringbuffer_init(&pipe->ringbuffer, buf, size);
 
+    pipe->flag = flag;
+
     /* create pipe */
     pipe->parent.type    = RT_Device_Class_Char;
     pipe->parent.init    = RT_NULL;
@@ -204,7 +249,7 @@ rt_err_t rt_pipe_detach(struct rt_pipe_device *pipe)
 RTM_EXPORT(rt_pipe_detach);
 
 #ifdef RT_USING_HEAP
-rt_err_t rt_pipe_create(const char *name, rt_size_t size)
+rt_err_t rt_pipe_create(const char *name, enum rt_pipe_flag flag, rt_size_t size)
 {
     rt_uint8_t *rb_memptr = RT_NULL;
     struct rt_pipe_device *pipe = RT_NULL;
@@ -223,7 +268,7 @@ rt_err_t rt_pipe_create(const char *name, rt_size_t size)
         return -RT_ENOMEM;
     }
 
-    return rt_pipe_init(pipe, name, rb_memptr, size);
+    return rt_pipe_init(pipe, name, flag, rb_memptr, size);
 }
 RTM_EXPORT(rt_pipe_create);