spi驱动求助：CS的控制权以及bus lock是否应该开放给用户

发布于 2017-04-06 15:16:23 浏览：3130 订阅该版

如题，若某spi设备需要如下操作
```cs0;
spi_write(XX);
delay(1);
control_spidevIO();
xxx=spi_read();
delay(1);
cs1;```

由于spi_dev中的rt_spi_send_then_send、rt_spi_send_then_recv、rt_spi_transfer 三个操作函数中不能添加 类似delay、control_spidevIO();或者说：spi读写操作时CS不能受用户控制。
是否应该添加更灵活的操作方法：
去掉：    
```result = rt_mutex_take(&(device->bus->lock), RT_WAITING_FOREVER);
rt_mutex_release(&(device->bus->lock));```
改写
```       message.cs_take    = 0;
       message.cs_release = 0;```
让设备驱动程序去调用rt_spi_take_bus、rt_spi_release_bus、rt_spi_take、rt_spi_release 方法

如：
```rt_size_t rt_spi_transfer_n(struct rt_spi_device *device,
                          const void           *send_buf,
                          void                 *recv_buf,
                          rt_size_t             length)
{
    rt_err_t result;
    struct rt_spi_message message;

RT_ASSERT(device != RT_NULL);
    RT_ASSERT(device->bus != RT_NULL);
    if (result == RT_EOK)
    {
        if (device->bus->owner != device)
        {
            /* not the same owner as current, re-configure SPI bus */
            result = device->bus->ops->configure(device, &device->config);
            if (result == RT_EOK)
            {
                /* set SPI bus owner */
                device->bus->owner = device;
            }
            else
            {
                /* configure SPI bus failed */
                rt_set_errno(-RT_EIO);
                result = 0;
                goto __exit;
            }
        }

/* initial message */
        message.send_buf   = send_buf;
        message.recv_buf   = recv_buf;
        message.length     = length;
        message.cs_take    = 0;
        message.cs_release = 0;
        message.next       = RT_NULL;

/* transfer message */
        result = device->bus->ops->xfer(device, &message);
        if (result == 0)
        {
            rt_set_errno(-RT_EIO);
            goto __exit;
        }
    }
    else
    {
        rt_set_errno(-RT_EIO);

return 0;
    }

__exit:

return result;
}```