invalid address returned by usb_alloc_coherent on dockstar

[MacLaren, James M]

>> I have been working on getting mythtv to run on my dockstar mostly
with
>> success.  I can record from the hd-homerun a network atsc/qam tv
tuner.
>> I understand from reading mailing list that a usb recorder (HVR-1950)
>> has been made to work on a sheeva plug.  I am trying to get the
>> Hauppuage hdpvr to work.  The driver is relatively new but seems to
work
>> stablely on i386 systems.  I am hoping someone can help with the
>> problem.
>> 
>>  
>> 
>> The call to 
>> 
>> mem = usb_alloc_coherent(dev->udev, dev->bulk_in_size, GFP_KERNEL,
>> 
>> &urb->transfer_dma);
>> 
>>  
> 
>> in hdvpr-video.c
>> 
>>  
>> 
>> Returns an address ffc11c00 which is not valid when I check it with
>> virt_addr_valid.  So the driver then exits gracefully later on.

>Correct.  Addresses returned from dma_alloc_coherent() may be remapped
>by architectures if that's what they need to do to achieve coherence.
>:ARM is such an architecture.

>In that case, the returned address will not pass the >virt_addr_valid()
>test, which only returns true for addresses within the kernel direct-
>mapped RAM region.

>It sounds like your driver has been written to only support x86.  I
>suggest you raise it as a bug against the driver.

Thanks for the clarification.  I will contact the author of the driver.

I am sure this is an ignorant question but how does one then use that
address if it has been remapped?  

In following through the hdpvr driver the address get stored for that
urb by usb_fill_bulk_urb 

The driver fails when it later calls  usb_submit_urb and that address is
checked in dma_map_single by virt_addr_valid

Should the driver save a different address mapped from the one returned
by usb_alloc_coherent and one that is valid if so do you know  how or
where I can see some examples/documentation.