Need advice: whether to flash DLink DWL-520

Jouni Malinen jkmaline at cc.hut.fi
Tue Aug 12 23:41:37 EDT 2003


On Tue, Aug 12, 2003 at 11:01:13PM -0400, James B. Hiller wrote:

> > Yes, you should consider upgrading the firmware. That combination of
> > PRI/STA firmware is known to have a bug that causes corruption of data
> > on PCI bus. This was fixed in PRI 1.0.7 / STA 1.3.5, so it or anything
> > newer is probably better solution.

> I'd seen that reference before, I think on seattlewireless.org.
> For my clarity:  is this something DLink themselves would be aware of,
> or is it something they specifically would NOT be aware of (or would
> disavow knowledge of) since it only happens in host ap mode, and they
> don't market the card for that purpose?

Assuming they are following information available from Intersil about
changes in firmware versions, they most certainly should be aware of the
issues. This particular problem causes problems in all modes so it is
not limited to Host AP in any way.

> Also, can you tell me anything about the likely observable behavior of
> this bug happening?  Like, are we talking system crash, or slow card
> throughput, or what?  (Not arguing; just learning).

This issue corrupts at least contents of received frames. This can show
up in odd looking error messages from the driver (like unknown port or
invalid length of the packet, etc.) and corrupted data frames (likely to
be dropped by TCP/IP stack). Consequently, it can drop throughput quite
a bit. I do not remember exact numbers, but comparing card with
1.0.5/1.3.4 to one with 1.0.7/1.3.5 showed huge difference in one of my
test systems.

Host AP driver is not supposed to crash with any data corruption from
the card; if it does, it should be fixed not to crash ;-). Anyway, I
have never seen a crash that would have been explained by corruption
caused by this issue.

> Yep, been told that.  (CVS intimidates me - any thought on when next
> release will be out?)

Sorry, no.

> I have no particular desire/intent to use two different ones.  It had
> just occurred to me that since I had at first been using the card just
> in ad hoc mode, to get it running I compiled in these two items
> above (config_hermes and config_pci_hermes); and then when I got
> hostap (pci) and built it, I neglected to un-config these drivers, so
> I was wondering if I should now go rebuild the kernel without them.

Both driver are trying to control the same hardware if you have them
loaded at the same time. I have never tested that kind of configuration,
but I would guess that Linux PCI code would select one of them based on
the order they were registered.. You might have hard time overriding the
one linked into the kernel with a kernel module.

-- 
Jouni Malinen                                            PGP id EFC895FA



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