Johannes Berg | 2 Aug 13:48 2007
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Re: [RFC V2] bcm43xx-mac80211: Provide information to allow transmission rate decreases

On Thu, 2007-08-02 at 13:37 +0200, Michael Buesch wrote:

> If we just check the ack bit, rate control would throttle, just because
> we sent unacked frames.

Ah but rate control shouldn't actually care about frames that we never
expected an ACK for since there's no way to know for those anyway. So
IMHO the rate control algorithm shouldn't even be called for those
frames.

> So if we didn't get an ack, we need to check if we failed, or if...
> Oh, acutally. Why not simply check the noack bit in the tx_control... :)

Works too, but it seems mac80211 should do that.

johannes
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Winkler, Tomas | 2 Aug 14:17 2007
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RE: [ipw3945-devel] chaning mode only when interface down?


>-----Original Message-----
>From: ipw3945-devel-bounces@...
[mailto:ipw3945-devel-
>bounces@...] On Behalf Of dragoran
>Sent: Thursday, August 02, 2007 12:17 PM
>To: Johannes Berg
>Cc: Dan Williams; linux-wireless@...; network manager;
ipw3945-
>devel@...
>Subject: Re: [ipw3945-devel] chaning mode only when interface down?
>
>Johannes Berg wrote:
>> On Thu, 2007-08-02 at 09:44 +0200, dragoran wrote:
>>
>>> I noticed that I have to do ifdown wlan0 before I can change the
mode
>>> with iwconfig.
>>> When I do it while the interface is up I get a error that the device
is
>>> busy.
>>>
>>
>> It is busy.
>>
>>
>ok
>>> It seems to happen with ad-hoc, master and back from them to
managed.
>>> Is this a bug in the iwlwifi driver or in mac80211 ?
(Continue reading)

Johannes Berg | 2 Aug 14:34 2007
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RE: [ipw3945-devel] chaning mode only when interface down?

On Thu, 2007-08-02 at 15:17 +0300, Winkler, Tomas wrote:

> There is a definitely a known issue in the driver that we still need to
> resolve, but I agree with Johannes that there is a problem in design of
> the configuration as well. 

Nono, you cannot solve it in the driver. The whole design of mac80211
mandates that assumption and I think it is a valid one to make. If
userspace breaks because of that it's their fault.

johannes
Winkler, Tomas | 2 Aug 14:41 2007
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RE: [ipw3945-devel] chaning mode only when interface down?


>-----Original Message-----
>From: Johannes Berg [mailto:johannes@...]
>Sent: Thursday, August 02, 2007 3:34 PM
>To: Winkler, Tomas
>Cc: dragoran; Dan Williams; linux-wireless@...; network
>manager; ipw3945-devel@...
>Subject: RE: [ipw3945-devel] chaning mode only when interface down?
>
>On Thu, 2007-08-02 at 15:17 +0300, Winkler, Tomas wrote:
>
>> There is a definitely a known issue in the driver that we still need
to
>> resolve, but I agree with Johannes that there is a problem in design
of
>> the configuration as well.
>
>Nono, you cannot solve it in the driver. The whole design of mac80211
>mandates that assumption and I think it is a valid one to make. If
>userspace breaks because of that it's their fault.
>
I know for sure there is an issue in our driver for moving to master
(AP) mode. I'm just cleaning up this patch...

I'm really not an expert on the configuration but I think at least the
transition from STA to IBSS mode and back should be smooth without
reloading the driver. What you do if the driver is compiled to kernel
will we reboot?

I hope we are talking about the same issue here...
(Continue reading)

Johannes Berg | 2 Aug 14:46 2007
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Re: chaning mode only when interface down?

On Thu, 2007-08-02 at 15:41 +0300, Winkler, Tomas wrote:

> I'm really not an expert on the configuration but I think at least the
> transition from STA to IBSS mode and back should be smooth without
> reloading the driver. What you do if the driver is compiled to kernel
> will we reboot?

Oh you don't have to reload the driver, you only have to down the
interface. If you have to reload it that's a driver bug, but the fact
that you have to down the interface is a mac80211 "limitation"

johannes
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dragoran | 2 Aug 14:48 2007
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Re: [ipw3945-devel] chaning mode only when interface down?

Johannes Berg wrote:
> On Thu, 2007-08-02 at 15:17 +0300, Winkler, Tomas wrote:
>
>   
>> There is a definitely a known issue in the driver that we still need to
>> resolve, but I agree with Johannes that there is a problem in design of
>> the configuration as well. 
>>     
>
> Nono, you cannot solve it in the driver. The whole design of mac80211
> mandates that assumption and I think it is a valid one to make.
why? did the old way (allow mode changing while up) caused any problems?

Johannes Berg | 2 Aug 14:53 2007
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Re: [ipw3945-devel] chaning mode only when interface down?

On Thu, 2007-08-02 at 14:48 +0200, dragoran wrote:

> > Nono, you cannot solve it in the driver. The whole design of mac80211
> > mandates that assumption and I think it is a valid one to make.
> why? did the old way (allow mode changing while up) caused any problems?

Why should it be allowed? Can you come up with a good reason for that
since you lose all state anyway when doing mode transitions?

Until then (and I guess somebody *really* wants it) it's just a lot
easier to not even try to change these low-level things while the
interface is operating.

johannes
Michael Buesch | 2 Aug 15:03 2007
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Re: [RFC V2] bcm43xx-mac80211: Provide information to allow transmission rate decreases

On Thursday 02 August 2007 13:48:39 Johannes Berg wrote:
> On Thu, 2007-08-02 at 13:37 +0200, Michael Buesch wrote:
> 
> > If we just check the ack bit, rate control would throttle, just because
> > we sent unacked frames.
> 
> Ah but rate control shouldn't actually care about frames that we never
> expected an ACK for since there's no way to know for those anyway. So
> IMHO the rate control algorithm shouldn't even be called for those
> frames.
> 
> > So if we didn't get an ack, we need to check if we failed, or if...
> > Oh, acutally. Why not simply check the noack bit in the tx_control... :)
> 
> Works too, but it seems mac80211 should do that.

So, what's the point of this "excessive retries" field anyway?
We already have an "acked" bit. So if it's not set, but we expected an
ack, what's the point of setting excessive retries in the driver?
the rc algo sould know _anyway_, as it has the "acked" and the
"we wanted to have an ack" bits.

confused..

--

-- 
Greetings Michael.
Johannes Berg | 2 Aug 15:07 2007
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Re: [RFC V2] bcm43xx-mac80211: Provide information to allow transmission rate decreases

On Thu, 2007-08-02 at 15:03 +0200, Michael Buesch wrote:

> So, what's the point of this "excessive retries" field anyway?
> We already have an "acked" bit. So if it's not set, but we expected an
> ack, what's the point of setting excessive retries in the driver?
> the rc algo sould know _anyway_, as it has the "acked" and the
> "we wanted to have an ack" bits.

No idea. I guess you get to dig through the code and remove it ;)

johannes
Tomas Winkler | 2 Aug 15:11 2007
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Re: [ipw3945-devel] chaning mode only when interface down?

On 8/2/07, Johannes Berg <johannes@...> wrote:
> On Thu, 2007-08-02 at 15:41 +0300, Winkler, Tomas wrote:
>
> > I'm really not an expert on the configuration but I think at least the
> > transition from STA to IBSS mode and back should be smooth without
> > reloading the driver. What you do if the driver is compiled to kernel
> > will we reboot?
>
> Oh you don't have to reload the driver, you only have to down the
> interface.
I suspected we are not talking about the same :)

If you have to reload it that's a driver bug, but the fact
> that you have to down the interface is a mac80211 "limitation"
>
Yes it is
> johannes
>
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Gmane