linux-kernel - Re: [ath5k-devel] [PATCH 1/1] ath5k: fix hw rate index condition

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Date:	Sun, 01 Mar 2009 00:21:52 -0500
From:	Pavel Roskin <proski@....org>
To:	Bob Copeland <me@...copeland.com>
Cc:	"Luis R. Rodriguez" <lrodriguez@...eros.com>,
	Jiri Slaby <jirislaby@...il.com>,
	"ath5k-devel@...ema.h4ckr.net" <ath5k-devel@...ema.h4ckr.net>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"John W. Linville" <linville@...driver.com>
Subject: Re: [ath5k-devel] [PATCH 1/1] ath5k: fix hw rate index condition

On Thu, 2009-02-26 at 22:06 -0500, Bob Copeland wrote:
> On Thu, Feb 26, 2009 at 06:39:12PM -0800, Luis R. Rodriguez wrote:
> > Might be worth adding a note why this is the case. Can't we simply avoid
> > this by checking earlier for the error or simply assigning it an actual
> > default _good_ hw rate value?
> 
> I guess an alternative is to initialize to 0, that would count any rx
> packets whose hw rate we don't know about as the base rate, so it would
> probably bias the RC to 1mb, but this is already one of those 'should 
> never happen' cases.

I would prefer that we don't hide problems.

If we don't know why we cannot get a valid rate, we should use WARN_ON
and find out why and when it happens.  I'm fine with using a bogus rate
with WARN_ON.

If we decide that we indeed cannot find the actual rate, then WARN_ON
should be removed and the bogus rate replaced with an "unknown rate",
that is, a special value that is never translated to a valid rate and
never given to any rate control algorithm.  Using a bogus rate without a
warning is wrong in my opinion.

It should be possible to represent "unknown rate" as such.  That applies
to all drivers.  I remember that b43 also failed to report the rate in
some cases (for the first received packet or something like that).

-- 
Regards,
Pavel Roskin
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