[vortex] Question about linux 3com driver

[Raymond Jennings]

Hello,
I have a question about your driver for 3Com for 905c & 905cx cards.  I
have been using these cards because the driver supports the NETIF_F_SG
option as well as checksum offloading.

I found through testing that this card/driver does not support zero-copy
for highmem pages.  I saw a comment in the code that said "Make NETIF_F_SG
dependent upon nr_free_highpages( ), not on CONFIG_HIGHMEM.

I'm curious about this comment.  Isn't it the case that zero-copy could
still work with CONFIG_HIGHMEM?  The only catch would be for skbuff's that
contain highmem pages the skbuff would have to be "linearized" which the
network stack does automatically (at least as of 2.4.16 possibly earlier.)

Do you disable NETIF_F_SG support if highmem pages exist?

Thanks.

Raymond B. Jennings III
IBM Thomas J. Watson Research Center
raymondj@us.ibm.com
(914)784-5475 (TL 863)