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device: add ref_count support

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This is a simple work around to the current device stack design. A
ref_count could let different modules to open/close the same device
independently without interfere others in some degree.

But there is still some data shared between the modules, like flag,
open_flag and user_data. Moreover, it won't yield an error if A open a
device, and B read from it before open it in B. Maybe alloc a new handle
in rt_device_open will be the ultimate solution. But that is much bigger
change and we may leave it to future development.
This commit is contained in:
Grissiom 2013-07-09 11:54:50 +08:00
parent 4f0cb88739
commit 7bcce9e87f
2 changed files with 29 additions and 1 deletions
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1
include/rtdef.h
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@ -779,6 +779,7 @@ struct rt_device
rt_uint16_t flag; /**< device flag */
rt_uint16_t open_flag; /**< device open flag */
rt_uint8_t ref_count; /**< reference count */
rt_uint8_t device_id; /**< 0 - 255 */
/* device call back */

29
src/device.c
View File

@ -1,7 +1,7 @@
/*
* File : device.c
* This file is part of RT-Thread RTOS
* COPYRIGHT (C) 2006 - 2012, RT-Thread Development Team
* COPYRIGHT (C) 2006 - 2013, RT-Thread Development Team
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@ -24,6 +24,7 @@
* 2012-10-20 Bernard add device check in register function,
* provided by Rob <rdent@iinet.net.au>
* 2012-12-25 Bernard return RT_EOK if the device interface not exist.
* 2013-07-09 Grissiom add ref_count support
*/
#include <rtthread.h>
@ -51,6 +52,7 @@ rt_err_t rt_device_register(rt_device_t dev,
rt_object_init(&(dev->parent), RT_Object_Class_Device, name);
dev->flag = flags;
dev->ref_count = 0;
return RT_EOK;
}
@ -237,6 +239,11 @@ rt_err_t rt_device_open(rt_device_t dev, rt_uint16_t oflag)
return -RT_EBUSY;
}
dev->ref_count++;
/* don't let bad things happen silently. If you are bitten by this assert,
* please set the ref_count to a bigger type. */
RT_ASSERT(dev->ref_count != 0);
/* call device open interface */
if (dev->open != RT_NULL)
{
@ -264,6 +271,14 @@ rt_err_t rt_device_close(rt_device_t dev)
RT_ASSERT(dev != RT_NULL);
if (dev->ref_count == 0)
return -RT_ERROR;
dev->ref_count--;
if (dev->ref_count != 0)
return RT_EOK;
/* call device close interface */
if (dev->close != RT_NULL)
{
@ -297,6 +312,12 @@ rt_size_t rt_device_read(rt_device_t dev,
{
RT_ASSERT(dev != RT_NULL);
if (dev->ref_count == 0)
{
rt_set_errno(-RT_ERROR);
return 0;
}
/* call device read interface */
if (dev->read != RT_NULL)
{
@ -329,6 +350,12 @@ rt_size_t rt_device_write(rt_device_t dev,
{
RT_ASSERT(dev != RT_NULL);
if (dev->ref_count == 0)
{
rt_set_errno(-RT_ERROR);
return 0;
}
/* call device write interface */
if (dev->write != RT_NULL)
{