On Thu, 25 Nov 2004, DMR wrote:

> Thanks for your respon.
> 
> I'm a newbie in linux USB device driver development.
> My detailed problem is described below.
> ----------++++++++
> My Problem in device driver is urb device pointer from usb core driver is 
> NULL.
> Case 1(Normal):
>   After resetting the power of USB device:
>      usb-uhci.c::uhci_interrupt() is called with the status value in nonzero.
>                  [status = inw(io_addr + USBSTS)]
>      usb-uhci.c::uhci_submit_urb() is called.
>      hub.c::usb_hub_events() is called, and port connection will be changed.
>      usb-uhci.c::uhci_submit_urb() is called again.
>      hub:c::usb_hub_disconnect() is called, and call usb.c::usb_disconnect()
>      usb device will be disconnected by device driver.
>      ..........
>      After device added(reconnected by hotplug), device driver will work 
> normally.
>      
>      
> Case 2(Error):
>   After resetting the power of USB device:
>      usb-uhci.c::uhci_interrupt() never called with the status value in 
> nonzero.
>      usb-uhci.c::uhci_submit_urb() is called.
>      hub.c::usb_hub_events() is called, and port connection will be changed.
>      usb-uhci.c::uhci_submit_urb() is called again.
>      hub:c::usb_hub_disconnect() is called, and call usb.c::usb_disconnect()
>      when disconnecting process in device driver run(not complete), 
>       bulk_read function(=device driver callback function) is called with
>       urb device pointer in NULL.
>    
>    In this case, there is no way to recover usb device driver but rebooting 
> system.
>    (reboot without resetting the power of USB device)
> 
> Case 2(Error case) is seldom happens.
> ++++++++----------
> 
> Now I'm analyzing Usb core driver source code to solve this problem.
> But I can't find a the solution.
> Is there any solution to solve this problem?
> 
> Best Regards
>  Marowa

The best solution is to use Linux 2.6 instead of Linux 2.4, if at all 
possible.  It has many fewer problems of this sort.

Alan Stern



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