On 04.02.2019 17:42, Thierry Reding wrote:
> From: Thierry Reding <tred...@nvidia.com>
>
> 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 <and...@lunn.ch>
> Signed-off-by: Thierry Reding <tred...@nvidia.com>
> ---
> 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;
>
I just have one concern / question:
After this there's a call to is_valid_ether_addr(mac_addr) and kernel-doc of
is_valid_ether_addr() states that argument must be u16-aligned.
AFAIK that's not guaranteed for a byte array.
Heiner
