netdev - Re: [PATCH net-next v1 1/1] net: dl2k: Use proper conversion of dev

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Date: Tue, 12 Dec 2023 11:23:44 +0000
From: Simon Horman <horms@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	kernel test robot <lkp@...el.com>
Subject: Re: [PATCH net-next v1 1/1] net: dl2k: Use proper conversion of
 dev_addr before IO to device

On Fri, Dec 08, 2023 at 05:33:27PM +0200, Andy Shevchenko wrote:
> The driver is using iowriteXX()/ioreadXX() APIs which are LE IO
> accessors simplified as
> 
>   1. Convert given value _from_ CPU _to_ LE
>   2. Write it to the device as is
> 
> The dev_addr is a byte stream, but because the driver uses 16-bit
> IO accessors, it wants to perform double conversion on BE CPUs,
> but it took it wrong, as it effectivelly does two times _from_ CPU
> _to_ LE. What it has to do is to consider dev_addr as an array of
> LE16 and hence do _from_ LE _to_ CPU conversion, followed by implied
> _from_ CPU _to_ LE in the iowrite16().
> 
> To achieve that, use get_unaligned_le16(). This will make it correct
> and allows to avoid sparse warning as reported by LKP.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202312030058.hfZPTXd7-lkp@intel.com/
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Thanks Andy,

I agree with your reasoning that the explicit conversion is reversed.

Reviewed-by: Simon Horman <horms@...nel.org>