[驱动范例]RAM DISK

发布于 2013-03-06 10:17:00 浏览：3887 订阅该版

测试时经常用到ram disk,虽然写了[wiki](http://www.rt-thread.org/dokuwiki/doku.php?id=rt_device_class_block)，但每次都是重新创建一个文件再粘贴代码，
所以把完整文件备份在这里以方便使用。
```#include <rtthread.h>
#include <string.h>

#define SECTOR_SIZE     (512)
#define RAM_DISK_SIZE   (1024*32)

static char ram_disk_buffer[RAM_DISK_SIZE];

/* 设备控制块 */
static struct rt_device ram_disk_device;

static rt_err_t ram_disk_init(rt_device_t dev)
{
    return RT_EOK;
}

static rt_err_t ram_disk_open(rt_device_t dev, rt_uint16_t oflag)
{
    return RT_EOK;
}

static rt_err_t ram_disk_close(rt_device_t dev)
{
    return RT_EOK;
}

static rt_size_t ram_disk_read(rt_device_t dev,
                               rt_off_t pos,
                               void* buffer,
                               rt_size_t size)
{
    memcpy(buffer, &ram_disk_buffer[SECTOR_SIZE * pos], SECTOR_SIZE * size);

return size;
}

static rt_size_t ram_disk_write(rt_device_t dev,
                                rt_off_t pos,
                                const void* buffer,
                                rt_size_t size)
{
    memcpy(&ram_disk_buffer[SECTOR_SIZE * pos], buffer, SECTOR_SIZE * size);

return size;
}

static rt_err_t ram_disk_control(rt_device_t dev,
                                 rt_uint8_t cmd,
                                 void *args)
{
    if (cmd == RT_DEVICE_CTRL_BLK_GETGEOME)
    {
        struct rt_device_blk_geometry *geometry;

geometry = (struct rt_device_blk_geometry *)args;
        if (geometry == RT_NULL) return -RT_ERROR;

geometry->bytes_per_sector = SECTOR_SIZE;
        geometry->sector_count = RAM_DISK_SIZE / SECTOR_SIZE;
        geometry->block_size = SECTOR_SIZE;
    }

return RT_EOK;
}

void rt_hw_ram_disk_init(void)
{
    /* 清零设备控制块 */
    memset(&ram_disk_device, 0, sizeof(ram_disk_device));

/* 初始化设备控制块 */
    ram_disk_device.type    = RT_Device_Class_Block;
    ram_disk_device.init    = ram_disk_init;
    ram_disk_device.open    = ram_disk_open;
    ram_disk_device.close   = ram_disk_close;
    ram_disk_device.read    = ram_disk_read;
    ram_disk_device.write   = ram_disk_write;
    ram_disk_device.control = ram_disk_control;

/* 向系统注册设备 */
    rt_device_register(&ram_disk_device, "ram_disk",
                       RT_DEVICE_FLAG_RDWR | RT_DEVICE_FLAG_STANDALONE);
}
```