Jason Thorpe wrote:
> 
> On Nov 24, 2004, at 7:54 AM, Neil Ludban wrote:
> 
>> I'm working on a new network driver under NetBSD/powerpc 2.0_RC3,
>> and discovered that the hardware goes off into an unexpected state
>> when it gets a DMA entry with length zero.  It's easily reproduced
>> with ping requests (see below), and goes away with a 2-line
>> workaround in _bus_dmamap_load_mbuf.  Does anybody have an opinion
>> as to the severity of this: can it be silently ignored as expected
>> mbuf behaviour, print a warning, or panic?
> 
> 
> I think it's probably reasonable to put the check into the bus_dma 
> functions.  While annoying, a zero-length mbuf is perfectly valid, so 
> it's probably best to just program defensively in the bus_dma back-ends.
> 
> Please file a PR about the problem, and I will be happy to make the 
> necessary modifications to the extant bus_dma back-ends.
> 
>         -- Jason R. Thorpe <thorpej@shagadelic.org>
> 

Here it is:

> Thank you very much for your problem report.
> It has the internal identification `kern/28411'.
> The individual assigned to look at your
> report is: kern-bug-people. 
> 
> 
>>Category:       kern
>>Responsible:    kern-bug-people
>>Synopsis:       bus_dmamap_load_mbuf may create zero length DMA segments
>>Arrival-Date:   Wed Nov 24 18:09:01 +0000 2004

-Neil