linux 2.6下编译usb驱动和arm板进行数据通信(2) linux, 通信

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static int lcd_release(struct inode *inode, struct file *file)
{
    struct usb_lcd *dev;

    dev = (struct usb_lcd *)file->private_data;
    if (dev == NULL)
        return -ENODEV;

    /* decrement the count on our device */
    kref_put(&dev->kref, lcd_delete);
    return 0;
}

static ssize_t lcd_read(struct file *file, char __user * buffer, size_t count, loff_t *ppos)
{
    struct usb_lcd *dev;
    int retval = 0;
    int bytes_read;

    dev = (struct usb_lcd *)file->private_data;

    /* do a blocking bulk read to get data from the device */
    retval = usb_bulk_msg(dev->udev,
                  usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),
                  dev->bulk_in_buffer,
                  min(dev->bulk_in_size, count),
                  &bytes_read, 30*60*1000);//gliethttp_20080527 修改超时时间
    /* if the read was successful, copy the data to userspace */
    if (!retval) {
        if (copy_to_user(buffer, dev->bulk_in_buffer, bytes_read))
            retval = -EFAULT;
        else
            retval = bytes_read;
    }

    return retval;
}