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

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Date:	Mon, 2 Mar 2009 22:46:00 -0500
From:	Bob Copeland <me@...copeland.com>
To:	Pavel Roskin <proski@....org>
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>, mickflemm@...il.com
Subject: Re: [ath5k-devel] [PATCH 1/1] ath5k: fix hw rate index condition

On Sun, Mar 01, 2009 at 12:21:52AM -0500, Pavel Roskin wrote:
> 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.

So here is at least stage one of this, not yet the global "unknown rate"
infrastructure, but hopefully it will allow us to track down the issue.

It makes hw_to_driver_rix a little uglier, but oh well.  Thoughts?

From: Bob Copeland <me@...copeland.com>
Date: Mon, 2 Mar 2009 21:55:18 -0500
Subject: [PATCH] ath5k: warn and correct rate for unknown hw rate indexes

ath5k sets up a mapping table from the hardware rate index to
the rate index used by mac80211; however, we have seen some
received frames with incorrect rate indexes.  Such frames
normally get dropped with a warning in __ieee80211_rx(), but the 
warning doesn't include enough context to track down the error.

This patch adds a warning to hw_to_driver_rix for any lookups
that result in a rate index of -1, then returns a valid rate so
the frame can be processed.

This also includes the bug fix suggested by Pavel Roskin, in which
the mapping table is made signed, so rates initialized to -1 stay
that way.

Signed-off-by: Bob Copeland <me@...copeland.com>
---
 drivers/net/wireless/ath5k/base.c |   15 ++++++++++++---
 drivers/net/wireless/ath5k/base.h |    2 +-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/ath5k/base.c b/drivers/net/wireless/ath5k/base.c
index f7c424d..8d4b11c 100644
--- a/drivers/net/wireless/ath5k/base.c
+++ b/drivers/net/wireless/ath5k/base.c
@@ -1100,9 +1100,18 @@ ath5k_mode_setup(struct ath5k_softc *sc)
 static inline int
 ath5k_hw_to_driver_rix(struct ath5k_softc *sc, int hw_rix)
 {
-	WARN(hw_rix < 0 || hw_rix >= AR5K_MAX_RATES,
-			"hw_rix out of bounds: %x\n", hw_rix);
-	return sc->rate_idx[sc->curband->band][hw_rix];
+	int rix;
+
+	/* return base rate on errors */
+	if (WARN(hw_rix < 0 || hw_rix >= AR5K_MAX_RATES,
+			"hw_rix out of bounds: %x\n", hw_rix))
+		return 0;
+
+	rix = sc->rate_idx[sc->curband->band][hw_rix];
+	if (WARN(rix < 0, "invalid hw_rix: %x\n", hw_rix))
+		rix = 0;
+
+	return rix;
 }
 
 /***************\
diff --git a/drivers/net/wireless/ath5k/base.h b/drivers/net/wireless/ath5k/base.h
index 20e0d14..8229561 100644
--- a/drivers/net/wireless/ath5k/base.h
+++ b/drivers/net/wireless/ath5k/base.h
@@ -112,7 +112,7 @@ struct ath5k_softc {
 	struct ieee80211_supported_band sbands[IEEE80211_NUM_BANDS];
 	struct ieee80211_channel channels[ATH_CHAN_MAX];
 	struct ieee80211_rate	rates[IEEE80211_NUM_BANDS][AR5K_MAX_RATES];
-	u8			rate_idx[IEEE80211_NUM_BANDS][AR5K_MAX_RATES];
+	s8			rate_idx[IEEE80211_NUM_BANDS][AR5K_MAX_RATES];
 	enum nl80211_iftype	opmode;
 	struct ath5k_hw		*ah;		/* Atheros HW */
 
-- 
1.6.0.6



-- 
Bob Copeland %% www.bobcopeland.com

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