Re: how can i make the skeleton read function blocking function?

Dear Oliver forgive me for my many questions but here are the
modificaions that u adviced me to do but i think there is still
something wrong because when the gadget sends "hello" for example to
the host, my computer is hanging so what is the error ,i m gonna be
made:

here is the last code for skel_read:


static void skel_read_bulk_callback(struct urb *urb, struct pt_regs *regs)
{
	struct usb_skel *dev;
	complete((struct completion *)urb->context);
	dev = (struct usb_skel *)urb->context;
	up(&dev->limit_sem);
}

static ssize_t skel_read(struct file *file, char *user_buffer, size_t
count, loff_t *ppos)

{
	struct completion done;
	struct usb_skel *dev;
	int retval = 0;
	struct urb *urb = NULL;
	char *buf = NULL;

	size_t readsize = min(count, (size_t)MAX_TRANSFER);

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

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

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

	init_completion(&done);

	/* 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_buffer_alloc(dev->udev, readsize, GFP_KERNEL, &urb->transfer_dma);
	if (!buf) {
		retval = -ENOMEM;
		goto error;
	}

	/* initialize the urb properly */
	usb_fill_bulk_urb(urb, dev->udev,
			  usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),
			  buf, readsize, skel_read_bulk_callback, &done);
	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

	/* send the data out the bulk port */
	retval = usb_submit_urb(urb, GFP_KERNEL);
	if (retval) {
		err("%s - failed submitting read urb, error %d", __FUNCTION__, retval);
		goto error;
	}

	wait_for_completion(&done);

	if (   copy_to_user(user_buffer, dev->bulk_in_buffer, urb->actual_length) )
		retval = -EFAULT;
	else
		retval = urb->actual_length;

	
	/* free up our allocated buffer */
	usb_buffer_free(urb->dev, urb->transfer_buffer_length,
			urb->transfer_buffer, urb->transfer_dma);
	/* release our reference to this urb, the USB core will eventually
free it entirely */
	usb_free_urb(urb);

	return retval;

exit:
	return retval;

error:
	usb_buffer_free(dev->udev, readsize, buf, urb->transfer_dma);
	usb_free_urb(urb);
	up(&dev->limit_sem);
	return retval;
}


thanks in advance
yours nesta

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