Re: Network Drivers

Donald Becker (becker@cesdis1.gsfc.nasa.gov)
Fri, 3 Sep 1999 14:44:22 -0400 (EDT)


On Fri, 3 Sep 1999, Alan Cox wrote:

> > Does anyone have drivers for sis900 10/100 ethernet card driver which works? I
> > have the source, but was told it was a buggy version of it... I'm a complete
> > newbie, so any help is appreciated.
> > I'm running mandrake 6.1
>
> The code in 2.2.12 is what we have from SiS so far. The 2nd revision from
> them

A few notes about the sis900 driver:

It's apparently derived from either/both pci-skeleton.c and rtl8139.c.
Many of the comments were specific to the rtl8139, and are incorrect.
(I tend to add comments only when the chip operation is atypical, so
copying driver comments is worse than just removing all of them.)

During link negotiation the driver may do up to 3600 iterations of
mdio_read()! Since the driver doesn't do preamble suppression (that code
isn't in the pci-skelton.c example), each mdio_read() call takes
165 PCI transactions. And this can happen every timer tick when there is
no link beat!

The driver always copies packets on both transmit and receive, when the
underlying chip should is able to transmit and receive directly to the
skbuffs. This also is the result of copying from the rtl8139 driver.
(The rtl8139 data transfer engine was influenced by Realtek's 8390 clone
design and is very primative.)

Donald Becker becker@cesdis.gsfc.nasa.gov
USRA-CESDIS, Center of Excellence in Space Data and Information Sciences.
Code 930.5, Goddard Space Flight Center, Greenbelt, MD. 20771
301-286-0882 http://cesdis.gsfc.nasa.gov/people/becker/whoiam.html

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