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

Bob Copeland
2009-03-03T03:47:01Z

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@bobcopeland.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@bobcopeland.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