question for developers (help plzz!!)

question for developers (help plzz!!)

[maali Al Janoob]

Dear all,

I would like to get in touch with any of the developers of Realtek and 
Ralink linux drivers. My question to them is about the implementation of the 
binary exponential backoff (BEB) algorithm in the driver: is it part of the 
open-source driver code which is availabl for public access, or is it part 
of the binary-only firmware?
I came to know thorugh this mailing list that those two chipsets might not 
require a firmware, and that gave me hope in finding all the 802.11 
functionalities in the open source driver codes, but I have searched through 
the code of the Ralink 2571 usb driver and the Realtek 8187L driver - What I 
found was only specifying the min and max values of the contention window 
(cw), not the implementation of the BEB algorithm itselt.

Aside from this, if any one is aware of any chipset that implements ALL 
802.11 funcitonalities in open source software, please save me with it. I'm 
doing a masters thesis that requires modifying the BEB algorithm. I have 
tried the following chips so far with no hope: prism (wlan-ng), 
zd1211(zd1211rw), atheros(madwifi).

The smallest contribution of any of you will be of great value to me!

Regards,
Maali

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Re: question for developers (help plzz!!)

[Johannes Berg]

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On Fri, 2007-08-17 at 00:54 +0400, maali Al Janoob wrote:

> I came to know thorugh this mailing list that those two chipsets might not 
> require a firmware, and that gave me hope in finding all the 802.11 
> functionalities in the open source driver codes,

Heh. No, that most likely just means that the stuff was in hardware or
the firmware is on a ROM.

> Aside from this, if any one is aware of any chipset that implements ALL 
> 802.11 funcitonalities in open source software, please save me with it.

Nope. I don't think there's one, it just doesn't make sense to implement
the backoff algorithm in software because it's too timing sensitive.

johannes

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Re: question for developers (help plzz!!)

[maali Al Janoob]

Thank you so much for the reply. My advisor is not very convinced with this 
answer, and says that there must be somewhere a linux driver that has an 
open source firmware for protocol development purposes, or a driver that 
implements everything in software. So, firstly, can I please ask you for 
some references affirming your answer that I can include in my research? and 
secondly, are you aware of any attempt in the open source firmware 
direction?

Assuming that there is no way I can access the backoff algorithm in any of 
the commercial wireless cards, what would be the solution to my case then? I 
need to modify the backoff algorithm for my masters thesis, and if this is 
not possible with any card, what should I do?!

Thank you


>From: Johannes Berg <johannes@sipsolutions.net>
>To: maali Al Janoob <mms82@hotmail.com>
>CC: linux-wireless@vger.kernel.org
>Subject: Re: question for developers (help plzz!!)
>Date: Fri, 17 Aug 2007 12:18:46 +0200
>
>On Fri, 2007-08-17 at 00:54 +0400, maali Al Janoob wrote:
>
> > I came to know thorugh this mailing list that those two chipsets might 
>not
> > require a firmware, and that gave me hope in finding all the 802.11
> > functionalities in the open source driver codes,
>
>Heh. No, that most likely just means that the stuff was in hardware or
>the firmware is on a ROM.
>
> > Aside from this, if any one is aware of any chipset that implements ALL
> > 802.11 funcitonalities in open source software, please save me with it.
>
>Nope. I don't think there's one, it just doesn't make sense to implement
>the backoff algorithm in software because it's too timing sensitive.
>
>johannes


><< signature.asc >>

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Re: question for developers (help plzz!!)

[maali Al Janoob]

Thank you so much for the reply. My advisor is not very convinced with this 
answer, and says that there must be somewhere a linux driver that has an 
open source firmware for protocol development purposes, or a driver that 
implements everything in software. So, firstly, can I please ask you for 
some references affirming your answer that I can include in my research? and 
secondly, are you aware of any attempt in the open source firmware 
direction?

Assuming that there is no way I can access the backoff algorithm in any of 
the commercial wireless cards, what would be the solution to my case then? I 
need to modify the backoff algorithm for my masters thesis, and if this is 
not possible with any card, what should I do?!

Thank you


>From: Johannes Berg <johannes@sipsolutions.net>
>To: maali Al Janoob <mms82@hotmail.com>
>CC: linux-wireless@vger.kernel.org
>Subject: Re: question for developers (help plzz!!)
>Date: Fri, 17 Aug 2007 12:18:46 +0200
>
>On Fri, 2007-08-17 at 00:54 +0400, maali Al Janoob wrote:
>
> > I came to know thorugh this mailing list that those two chipsets might 
>not
> > require a firmware, and that gave me hope in finding all the 802.11
> > functionalities in the open source driver codes,
>
>Heh. No, that most likely just means that the stuff was in hardware or
>the firmware is on a ROM.
>
> > Aside from this, if any one is aware of any chipset that implements ALL
> > 802.11 funcitonalities in open source software, please save me with it.
>
>Nope. I don't think there's one, it just doesn't make sense to implement
>the backoff algorithm in software because it's too timing sensitive.
>
>johannes


><< signature.asc >>

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Re: question for developers (help plzz!!)

[Johannes Berg]

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On Fri, 2007-08-17 at 15:49 +0400, maali Al Janoob wrote:
> Thank you so much for the reply. My advisor is not very convinced with this 
> answer, and says that there must be somewhere a linux driver that has an 
> open source firmware for protocol development purposes, or a driver that 
> implements everything in software.

Clearly, your adviser has no clue how things work wrt. Linux and 802.11.
There's gnuradio, but I don't think they already have a working 802.11
implementation. That your adviser thinks that there could be a driver
that implements retry logic in software is a pretty good indication for
something else that I'll refrain from mentioning though.... Retry logic
is timing sensitive on the order of a microsecond and Linux isn't a
real-time operating system. That should tell you at least something.

> So, firstly, can I please ask you for 
> some references affirming your answer that I can include in my research? 

No. Feel free to do the research yourself, I've only answered based on
my own (limited) knowledge.

> and 
> secondly, are you aware of any attempt in the open source firmware 
> direction?

We've partially reverse engineered the Broadcom firmware and others have
partially reverse engineered the prism54 firmware, neither have working
replacement firmware. In fact, for Broadcom firmware I haven't been able
to completely identify the retry logic in the existing code from a quick
look.

> Assuming that there is no way I can access the backoff algorithm in any of 
> the commercial wireless cards, 

I assure you, this is the case unless you want to invest significant
reverse engineering effort or somehow manage to get vendor support. But
as far as I know, for example Broadcom's NDA doesn't include firmware
because there's no reason for a card vendor to have access to it.

> what would be the solution to my case then? I 
> need to modify the backoff algorithm for my masters thesis, and if this is 
> not possible with any card, what should I do?!

Why would you be asking me this question? Remember it's your masters
thesis, not mine, you're the one supposed to solve the problems arising.
I'm told (by my thesis advisers, mind you) one of the points of doing a
Master's is showing that one is able to solve the arising problems.

johannes

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