Mmm.... I might be onto something about this weird MTU problem with Zydas 
1211b based devices on my embedded box.

This box has an RDC i486 SOC processor.

Within the vendor driver of the Zydas 1211b there is an extra compiler flag 
called "ZDCONF_R8610_FRAG_FIX" (r8610 is an RDC i486 compatible SOC), it is 
only tested in the vendor module zd1205c as follows:

(small snippet of code, arrow is mine)

   //copy packet for IP header is located on 4-bytes alignment
#if ZDCONF_R8610_FRAG_FIX == 1 
    if (1)
    if (length < RX_COPY_BREAK)
        skb = dev_alloc_skb(length+2);

        if (skb){
            skb->dev = g_dev;
            skb_reserve(skb, 2);
            skb_put(skb, length);
        skb->tail = 0;
        skb->data = pData;
        skb->tail = skb->data = pData;
        skb_put(skb, length);

i.e. if the flag is set in the receiver code a number of statements is 
always executed on an R8610...

I reckon this certainly might be the reason of my MTU > 500 problem... seems 

This weird patch is of course not present in the community driver.

Any comments?




----- Original Message ----- 
From: "Hin-Tak Leung" <hintak_le...@yahoo.co.uk>
To: <zd1211-devs@lists.sourceforge.net>; "Ernst J. Oud" 
Sent: Sunday, February 14, 2010 11:41 PM
Subject: Re: [zd1211-devs] Problem with MTU > 500

Hmm, what's the hardware (the zd1211rw: ... line in your dmesg, you can 
probably just grep zd1211 /var/log/message for it as well) may be all the 
same. There are quite a few variants.

I don't know if putting compat-wireless on will help, but you could give 
that a try. FWIW, the driver development has gone over to
linux-wireless.org and changes goes directly into wireless-testing git; the 
sourceforge zd1211 site isn't much more than the mailing list these days, 
and even the mailing list isn't very active. (try the linux-wireless list 
may be a good idea).

--- On Sun, 14/2/10, Ernst J. Oud <ernst...@euronet.nl> wrote:

> Ok.
> Did some further experimenting. I remembered having an
> Thomson st121g USB WLAN stick and tried that (Prism
> chipset). With the same distro and config it works fine
> using minstrel or pid; i.e. with an MTU of 1500 no problems
> whatsoever. If I bring the box down and use my zd1211 stick
> instead (some distro/config) and boot it, it doesn't work
> with any MTU > 500 using pid or minstrel.
> So this must be some zd1211rw driver issue. It isn't the
> slackware setup and not the hardware; i.e. not the embedded
> box since the st121g works fine on it and not the zd1211
> stick since I used three separate sticks (from three
> different manufacturers: icidu, msi and cc&c) and they
> all have the same problem.
> Any further clues?
> BTW; the svn for the zd1211rw driver shows that the latest
> version is 3 years old?
> Ernst

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