netdev - [PATCH net-next v2 06/10] drivers/net/ethernet: handle one warning explicitly

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Message-Id: <20200915014455.1232507-7-jesse.brandeburg@intel.com>
Date:   Mon, 14 Sep 2020 18:44:51 -0700
From:   Jesse Brandeburg <jesse.brandeburg@...el.com>
To:     netdev@...r.kernel.org
Cc:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        intel-wired-lan@...ts.osuosl.org
Subject: [PATCH net-next v2 06/10] drivers/net/ethernet: handle one warning explicitly

While fixing the W=1 builds, this warning came up because the
developers used a very tricky way to get structures initialized
to a non-zero value, but this causes GCC to warn about an
override. In this case the override was intentional, so just
disable the warning for this code with a macro that results
in disabling the warning for compiles on GCC versions after 8.

NOTE: the __diag_ignore macro currently only accepts a second
argument of 8 (version 80000)

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
---
 drivers/net/ethernet/renesas/sh_eth.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
index 586642c33d2b..c63304632935 100644
--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/drivers/net/ethernet/renesas/sh_eth.c
@@ -45,6 +45,15 @@
 #define SH_ETH_OFFSET_DEFAULTS			\
 	[0 ... SH_ETH_MAX_REGISTER_OFFSET - 1] = SH_ETH_OFFSET_INVALID
 
+/* use some intentionally tricky logic here to initialize the whole struct to
+ * 0xffff, but then override certain fields, requiring us to indicate that we
+ * "know" that there are overrides in this structure, and we'll need to disable
+ * that warning from W=1 builds. GCC has supported this option since 4.2.X, but
+ * the macros available to do this only define GCC 8.
+ */
+__diag_push();
+__diag_ignore(GCC, 8, "-Woverride-init",
+	      "logic to initialize all and then override some is OK");
 static const u16 sh_eth_offset_gigabit[SH_ETH_MAX_REGISTER_OFFSET] = {
 	SH_ETH_OFFSET_DEFAULTS,
 
@@ -332,6 +341,7 @@ static const u16 sh_eth_offset_fast_sh3_sh2[SH_ETH_MAX_REGISTER_OFFSET] = {
 
 	[TSU_ADRH0]	= 0x0100,
 };
+__diag_pop();
 
 static void sh_eth_rcv_snd_disable(struct net_device *ndev);
 static struct net_device_stats *sh_eth_get_stats(struct net_device *ndev);
-- 
2.28.0