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

From: Arnd Bergmann <arnd@arndb.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@arndb.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

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Mon, 27 Sep 2021 14:16:04 +0200 you wrote:

From: Arnd Bergmann <arnd@arndb.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 }

[...]

Here is the summary with links:
  - cxgb: avoid open-coded offsetof()
    https://git.kernel.org/netdev/net-next/c/ef5d6356e2ac

You are awesome, thank you!
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