[PATCH net-next] net: airoha: fix ARRAY_SIZE() division by zero on UP builds

[Lorenzo Bianconi <lorenzo@kernel.org>]

airoha_alloc_gdm_device() initializes the txq_lock[] array iterating
over ARRAY_SIZE(dev->txq_lock). ARRAY_SIZE() expands to
sizeof(dev->txq_lock) / sizeof((dev->txq_lock)[0]), but on UP builds
(CONFIG_SMP unset, CONFIG_DEBUG_SPINLOCK unset) arch_spinlock_t is an
empty struct, so sizeof(spinlock_t) is zero and the expression is a
compile-time division by zero (undefined behavior), reported by clang
as "division by zero is undefined [-Wdivision-by-zero]".

Since the array is statically sized with AIROHA_NUM_NETDEV_TX_RINGS,
use the named constant as loop bound instead of ARRAY_SIZE().

Fixes: 78a35725e533 ("net: airoha: defer GDM3/GDM4 WAN mode and GDM2 loopback to QoS offload")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202607311850.6p0ZUVq4-lkp@intel.com/
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 drivers/net/ethernet/airoha/airoha_eth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index dba7c52c0896..64619e9a704d 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -3467,7 +3467,7 @@ static int airoha_alloc_gdm_device(struct airoha_eth *eth,
 	netdev->dev.of_node = of_node_get(np);
 	dev = netdev_priv(netdev);
 	u64_stats_init(&dev->stats.syncp);
-	for (i = 0; i < ARRAY_SIZE(dev->txq_lock); i++)
+	for (i = 0; i < AIROHA_NUM_NETDEV_TX_RINGS; i++)
 		spin_lock_init(&dev->txq_lock[i]);
 	dev->port = port;
 	dev->eth = eth;

---
base-commit: 2fbade66245059c78daeaccfce13ecf499fffb51
change-id: 20260731-airoha-spinlock-array-fix-d239f7841cb8

Best regards,
-- 
Lorenzo Bianconi <lorenzo@kernel.org>