From: Heiner Kallweit <hkallweit1@gmail.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Thierry Reding <thierry.reding@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Realtek linux nic maintainers <nic_swsd@realtek.com>,
netdev@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] r8169: Load MAC address from device tree if present
Date: Fri, 25 Jan 2019 20:23:29 +0100 [thread overview]
Message-ID: <39547002-74f3-66c4-93ce-9adf72841b8e@gmail.com> (raw)
In-Reply-To: <20190125190715.GG22211@lunn.ch>
On 25.01.2019 20:07, Andrew Lunn wrote:
>> Andrew, for my understanding: What do you think is wrong with the
>> alignment requirement? It was introduced because we do a 32 bit access
>> to the start address of the array and want to avoid an unaligned access.
>
> Hi Heiner
>
> Because you are doing pointer aliasing, the compiler will by default
> generate bad code, doing unaligned access. Adding the attribute works
> around this. But it is just a work around. Since this is very slow
> path code, i would just avoid the pointer aliasing, write a bit more C
> code as Thierry suggested, and the optimiser will probably figure out
> what is going on and produce reasonable code.
>
> Also, in general, by avoiding pointer aliasing, you allow static code
> checkers to work better. They are more likely to discover buffer
> overruns, etc.
>
> Andrew
>
Thanks, good to know.
The following doesn't hurt us here, but things like this have to be
considered too. According to chip spec:
"The ID registers 0-5 are only permitted to write by 4-byte access.
Read access can be byte, word, or double word access."
Heiner
next prev parent reply other threads:[~2019-01-25 19:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-25 10:18 [PATCH] r8169: Load MAC address from device tree if present Thierry Reding
2019-01-25 14:57 ` Andrew Lunn
2019-01-25 15:33 ` Thierry Reding
2019-01-25 18:26 ` Heiner Kallweit
2019-01-25 19:07 ` Andrew Lunn
2019-01-25 19:23 ` Heiner Kallweit [this message]
2019-01-25 18:34 ` Heiner Kallweit
2019-01-29 17:40 ` Thierry Reding
2019-01-29 18:51 ` Heiner Kallweit
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