Question

我需要制作一个Linux驱动程序来控制某些第三方组件。该组件没有非易失性存储器，因此初始化的一部分涉及到我连续发送一堆USB传输来加载设备固件。

为此，我正在复制this源代码以制作基本的Linux USB驱动程序。当我连接外部组件之前，所有的设置和检测功能似乎都可以正常工作，直到尝试加载固件。

使用以下功能：

    static ssize_t skel_write(struct file *file, const char *user_buffer,
              size_t count, loff_t *ppos)
{
    struct usb_skel *dev;
    int retval = 0;
    struct urb *urb = NULL;
    char *buf = NULL;
    size_t writesize = min(count, (size_t)MAX_TRANSFER);

    dev = file->private_data;

    /* verify that we actually have some data to write */
    if (count == 0)
        goto exit;

    /*
     * limit the number of URBs in flight to stop a user from using up all
     * RAM
     */
    if (!(file->f_flags & O_NONBLOCK)) {
        if (down_interruptible(&dev->limit_sem)) {
            retval = -ERESTARTSYS;
            goto exit;
        }
    } else {
        if (down_trylock(&dev->limit_sem)) {
            retval = -EAGAIN;
            goto exit;
        }
    }

    spin_lock_irq(&dev->err_lock);
    retval = dev->errors;
    if (retval < 0) {
        /* any error is reported once */
        dev->errors = 0;
        /* to preserve notifications about reset */
        retval = (retval == -EPIPE) ? retval : -EIO;
    }
    spin_unlock_irq(&dev->err_lock);
    if (retval < 0)
        goto error;

    /* create a urb, and a buffer for it, and copy the data to the urb */
    urb = usb_alloc_urb(0, GFP_KERNEL);
    if (!urb) {
        retval = -ENOMEM;
        goto error;
    }

    buf = usb_alloc_coherent(dev->udev, writesize, GFP_KERNEL,
                 &urb->transfer_dma);
    if (!buf) {
        retval = -ENOMEM;
        goto error;
    }

    if (copy_from_user(buf, user_buffer, writesize)) {
        retval = -EFAULT;
        goto error;
    }

    /* this lock makes sure we don't submit URBs to gone devices */
    mutex_lock(&dev->io_mutex);
    if (!dev->interface) {      /* disconnect() was called */
        mutex_unlock(&dev->io_mutex);
        retval = -ENODEV;
        goto error;
    }

    /* initialize the urb properly */
    usb_fill_bulk_urb(urb, dev->udev,
              usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
              buf, writesize, skel_write_bulk_callback, dev);
    urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
    usb_anchor_urb(urb, &dev->submitted);

    /* send the data out the bulk port */
    retval = usb_submit_urb(urb, GFP_KERNEL);
    mutex_unlock(&dev->io_mutex);
    if (retval) {
        dev_err(&dev->interface->dev,
            "%s - failed submitting write urb, error %d\n",
            __func__, retval);
        goto error_unanchor;
    }

    /*
     * release our reference to this urb, the USB core will eventually free
     * it entirely
     */
    usb_free_urb(urb);


    return writesize;

error_unanchor:
    usb_unanchor_urb(urb);
error:
    if (urb) {
        usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
        usb_free_urb(urb);
    }
    up(&dev->limit_sem);

exit:
    return retval;
}

要加载固件，我需要发送大约50个USB事务。大约8点之后，我开始看到错误ERESTARTSYS。发生这种情况之后，所有后续的USB事务都会失败，然后如果我再试一次，我将在第一次尝试的事务中收到错误消息。

基于注释“限制正在运行的URB数量以阻止用户用完所有RAM”，似乎前8个URB已安排好了，但从未解决，此后缓冲区已满，因此所有后续尝试都是拒绝了。

但是，似乎没有其他错误消息发生，尝试进行初始化时，系统仅等待并且不报告尝试的USB事务的任何错误。

我如何确定正在进行的USB交易的状态，以查看为何未进行交易？

USB URB成功提交，然后挂起

0 个答案: