Re: USB net device unexpectedly stops sending driver bulk in urbs

On Sun, 2 Dec 2007, Andrew Bird wrote:

> Hi All,
> 	I'm new to the list so please be gentle ;-)
> 
> 	I'm experimenting with a USB network type device. I have a driver functioning 
> mostly, but during an example FTP download, the device unexpectedly stops 
> sending the host bulk in URBs.

You say that the device stops sending bulk-in data, but do you actually
mean that the driver stops submitting bulk-in URBs?

> If I send a single ping out sometimes the 
> transfer resumes. The missing data seems to have been buffered somewhere in 
> USBland, because the next set of URBs are larger than usual and 
> instantaneously available.

What do you mean by "instantaneously"?  How do you know the data isn't 
stuck in a network buffer rather than a USB buffer?

>  Has anyone any ideas as to why this is happening, 
> and how I might cure it?

Here's an answer at about the same level of detail as the information 
you provided:

	There's a bug in either the device or in your driver.

The answers to my questions above might help pin down where the bug
lies.  As for curing it, that's simple: If the bug is in the device,
add a workaround to your driver; if the bug is in your driver, fix it.

If you want a more useful answer, you'll have to provide more detailed
information.  For example: the kernel version, the type of USB host
controller, the dmesg log, any other debugging info, and maybe even the
driver source.

Alan Stern


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