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

Am Dienstag, 24. April 2007 13:19 schrieb Wael Adel:
 
> so these are the required modifications required to wait until the urb
> is finished then i can transfer the read data to the user-space
> 
> ***********************************************************************************************************************
> 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;
> 
> 
> 	/* sync/async unlink faults aren't errors */
> 	if (urb->status &&
> 	    !(urb->status == -ENOENT ||
> 	      urb->status == -ECONNRESET ||
> 	      urb->status == -ESHUTDOWN)) {
> 		dbg("%s - nonzero write bulk status received: %d",
> 		    __FUNCTION__, urb->status);
> 	}
> 
> 	/* free up our allocated buffer */
> 	usb_buffer_free(urb->dev, urb->transfer_buffer_length,
> 			urb->transfer_buffer, urb->transfer_dma);

Don't free the buffer here. You want to read from it.

> 	up(&dev->limit_sem);
> }
> 
> static ssize_t skel_read(struct file *file, const char *user_buffer,
> size_t count, loff_t *ppos)
> {
> 	struct completion done;

You need to call init_completion() on that before you use it.

> 	struct usb_skel *dev;
> 	int retval = 0,readbytes;
> 	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 write */

read that would be

> 	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;
> 	}
> 
> 	/* 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, dev);

You must pass a pointer to done, not dev.

> 	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 write urb, error %d", __FUNCTION__, retval);

write?

> 		goto error;
> 	}
> 
> 	wait_for_completion(&done);
> 
> 	if (   copy_to_user(user_buffer, dev->bulk_in_buffer, readbytes) )
> 		retval = -EFAULT;
> 	else
> 		retval = readbytes;

1. Here you need to free the URB and the buffer
2. You must deal with your device delivering less bytes than you asked for
You can use urb->actual_length
 
> 	return retval;
> 
> 	/* release our reference to this urb, the USB core will eventually
> free it entirely */
> 	usb_free_urb(urb);
> 
> exit:
> 	return readsize;
> 
> error:
> 	usb_buffer_free(dev->udev, readsize, buf, urb->transfer_dma);
> 	usb_free_urb(urb);
> 	up(&dev->limit_sem);
> 	return retval;
> }
> *********************************************************************************************************************
> is it right? or there is something else i should adjust.
> thanks in advance.
> 
> >
> > 	HTH
> > 		Oliver
> > --
> > SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
> > This signature is a legal requirement
> >
> 

-- 
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
This signature is a legal requirement

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