linux-kernel - Re: [PATCH v3 2/2] r8169: Avoid pointer aliasing

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Date:   Wed, 6 Feb 2019 13:35:08 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>, Joe Perches <joe@...ches.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Paul Zimmerman <pauldzim@...il.com>,
        Michal Kubecek <mkubecek@...e.cz>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] r8169: Avoid pointer aliasing

On Wed, Feb 06, 2019 at 01:30:18PM +0100, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.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 <andrew@...n.ch>
> Signed-off-by: Thierry Reding <treding@...dia.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.
> 
> Changes in v3:
> - align MAC address to u16 for is_valid_ether_addr()
> 
>  drivers/net/ethernet/realtek/r8169.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)

I also forgot Andrew's Reviewed-by here, but technically the patch has
changed, so I'll leave it up to him to confirm he's still okay with this
version.

Thierry

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