linux-kernel - [PATCH] cxgb: avoid open-coded offsetof()

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Message-Id: <20210927121611.940046-1-arnd@kernel.org>
Date:   Mon, 27 Sep 2021 14:16:04 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: [PATCH] cxgb: avoid open-coded offsetof()

From: Arnd Bergmann <arnd@...db.de>

clang-14 does not like the custom offsetof() macro in vsc7326:

drivers/net/ethernet/chelsio/cxgb/vsc7326.c:597:3: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]
                HW_STAT(RxUnicast, RxUnicastFramesOK),
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/chelsio/cxgb/vsc7326.c:594:56: note: expanded from macro 'HW_STAT'
        { reg, (&((struct cmac_statistics *)NULL)->stat_name) - (u64 *)NULL }

Rewrite this to use the version provided by the kernel.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/ethernet/chelsio/cxgb/vsc7326.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb/vsc7326.c b/drivers/net/ethernet/chelsio/cxgb/vsc7326.c
index 873c1c7b4ca0..a19284bdb80e 100644
--- a/drivers/net/ethernet/chelsio/cxgb/vsc7326.c
+++ b/drivers/net/ethernet/chelsio/cxgb/vsc7326.c
@@ -591,7 +591,7 @@ static void port_stats_update(struct cmac *mac)
 	} hw_stats[] = {
 
 #define HW_STAT(reg, stat_name) \
-	{ reg, (&((struct cmac_statistics *)NULL)->stat_name) - (u64 *)NULL }
+	{ reg, offsetof(struct cmac_statistics, stat_name) / sizeof(u64) }
 
 		/* Rx stats */
 		HW_STAT(RxUnicast, RxUnicastFramesOK),
-- 
2.29.2