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[217.229.16.64]) by smtp.gmail.com with ESMTPSA id f8sm2374772wrv.41.2019.02.04.08.42.16 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 04 Feb 2019 08:42:16 -0800 (PST) From: Thierry Reding To: "David S. Miller" Cc: Heiner Kallweit , Andrew Lunn , Realtek linux nic maintainers , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/2] r8169: Avoid pointer aliasing Date: Mon, 4 Feb 2019 17:42:13 +0100 Message-Id: <20190204164213.30727-2-thierry.reding@gmail.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190204164213.30727-1-thierry.reding@gmail.com> References: <20190204164213.30727-1-thierry.reding@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thierry Reding Read MAC address 32-bit at a time and manually extract the individual bytes. This avoids pointer aliasing and gives the compiler a better chance of optimizing the operation. Suggested-by: Andrew Lunn Signed-off-by: Thierry Reding --- Applies to net-next. I tested this on a Jetson TX2 with an add-in Realtek ethernet card that has a properly programmed OTP to verify that I got the endianess right. Seems like everything works and the device behaves the same with or without this patch. drivers/net/ethernet/realtek/r8169.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c index 501891be7c56..192fbb36bc9f 100644 --- a/drivers/net/ethernet/realtek/r8169.c +++ b/drivers/net/ethernet/realtek/r8169.c @@ -7113,12 +7113,21 @@ static int rtl_alloc_irq(struct rtl8169_private *tp) static void rtl_read_mac_address(struct rtl8169_private *tp, u8 mac_addr[ETH_ALEN]) { + u32 value; + /* Get MAC address */ switch (tp->mac_version) { case RTL_GIGA_MAC_VER_35 ... RTL_GIGA_MAC_VER_38: case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_51: - *(u32 *)&mac_addr[0] = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC); - *(u16 *)&mac_addr[4] = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC); + value = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC); + mac_addr[0] = (value >> 0) & 0xff; + mac_addr[1] = (value >> 8) & 0xff; + mac_addr[2] = (value >> 16) & 0xff; + mac_addr[3] = (value >> 24) & 0xff; + + value = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC); + mac_addr[4] = (value >> 0) & 0xff; + mac_addr[5] = (value >> 8) & 0xff; break; default: break; @@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp) static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent) { const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data; - u8 mac_addr[ETH_ALEN] __aligned(4) = {}; + u8 mac_addr[ETH_ALEN] = {}; struct rtl8169_private *tp; struct net_device *dev; int chipset, region, i; -- 2.19.1