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Message-Id: <20230214132025.1532147-1-arnd@kernel.org>
Date: Tue, 14 Feb 2023 14:20:21 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Johannes Berg <johannes@...solutions.net>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Arnd Bergmann <arnd@...db.de>, Felix Fietkau <nbd@....name>,
Alexander Wetzel <alexander@...zel-home.de>,
Toke Høiland-Jørgensen <toke@...e.dk>,
Andrei Otcheretianski <andrei.otcheretianski@...el.com>,
linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] wifi: mac80211: avoid u32_encode_bits() warning
From: Arnd Bergmann <arnd@...db.de>
gcc-9 triggers a false-postive warning in ieee80211_mlo_multicast_tx()
for u32_encode_bits(ffs(links) - 1, ...), since ffs() can return zero
on an empty bitmask, and the negative argument to u32_encode_bits()
is then out of range:
In file included from include/linux/ieee80211.h:21,
from include/net/cfg80211.h:23,
from net/mac80211/tx.c:23:
In function 'u32_encode_bits',
inlined from 'ieee80211_mlo_multicast_tx' at net/mac80211/tx.c:4437:17,
inlined from 'ieee80211_subif_start_xmit' at net/mac80211/tx.c:4485:3:
include/linux/bitfield.h:177:3: error: call to '__field_overflow' declared with attribute error: value doesn't fit into mask
177 | __field_overflow(); \
| ^~~~~~~~~~~~~~~~~~
include/linux/bitfield.h:197:2: note: in expansion of macro '____MAKE_OP'
197 | ____MAKE_OP(u##size,u##size,,)
| ^~~~~~~~~~~
include/linux/bitfield.h:200:1: note: in expansion of macro '__MAKE_OP'
200 | __MAKE_OP(32)
| ^~~~~~~~~
Newer compiler versions do not cause problems with the zero argument
because they do not consider this a __builtin_constant_p().
It's also harmless since the hweight16() check already guarantees
that this cannot be 0.
Replace the ffs() with an equivalent find_first_bit() check that
matches the later for_each_set_bit() style and avoids the warning.
Fixes: 963d0e8d08d9 ("wifi: mac80211: optionally implement MLO multicast TX")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
net/mac80211/tx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index defe97a31724..118648af979c 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -4434,7 +4434,7 @@ static void ieee80211_mlo_multicast_tx(struct net_device *dev,
u32 ctrl_flags = IEEE80211_TX_CTRL_MCAST_MLO_FIRST_TX;
if (hweight16(links) == 1) {
- ctrl_flags |= u32_encode_bits(ffs(links) - 1,
+ ctrl_flags |= u32_encode_bits(find_first_bit(&links, 16) - 1,
IEEE80211_TX_CTRL_MLO_LINK);
__ieee80211_subif_start_xmit(skb, sdata->dev, 0, ctrl_flags,
--
2.39.1
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