Re: hme(4) hardware RX checksum

[Darren Reed <darrenr%netbsd.org@localhost>]

Have you read this:
http://gdamore.blogspot.com/2007/08/hme-checksum-limitations.html

You might want to follow up with Garrett directly, to see
if he has any tips/comments on the hardware itself.

Izumi Tsutsui wrote:
...
> 
> hme(4) seems to provide a dumb checksum for data after the IP header,
> so I'm not sure if it can provide proper checksum even for
> ETHERTYPE_VLAN packets. With a quick test, VLAN packets are
> also swcsum'ed.
> 
> Currently hme(4) and gem(4) have the similar code which decodes
> RX packet headers to adjust (deducting IP option sum etc.)
> a dumb checksum data provided by hardware.
> fxp(4) (i82559) also has the similar RX checksum hardware so
> I wonder how we can share a common function to decode RX packets
> for such dumb RX M_CSUM_DATA checksums.
...

With respect to this question, yes, it seems that it might
be a worthwhile idea for this functionality to bubble up
into the common ethernet code.

Darren