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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Arnd Bergmann , Felix Fietkau , Alexander Wetzel , =?utf-8?q?Toke_H=C3=B8iland-J?= =?utf-8?q?=C3=B8rgensen?= , Andrei Otcheretianski , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] wifi: mac80211: avoid u32_encode_bits() warning Date: Tue, 14 Feb 2023 14:20:21 +0100 Message-Id: <20230214132025.1532147-1-arnd@kernel.org> X-Mailer: git-send-email 2.39.1 MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1757812991370003354?= X-GMAIL-MSGID: =?utf-8?q?1757812991370003354?= From: Arnd Bergmann 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 --- 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,