linux-kernel - Re: [PATCH v2] drivers: net: xgene: Rewrite loop in xgene_enet_ecc

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Message-ID: <CAMuHMdW9W962ofhQYCEZY4OWpDLSYFEZknN5nz6OwaWnTKzEQw@mail.gmail.com>
Date:	Thu, 23 Oct 2014 09:05:27 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	David Miller <davem@...emloft.net>
Cc:	Iyappan Subramanian <isubramanian@....com>, kchudgar@....com,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drivers: net: xgene: Rewrite loop in xgene_enet_ecc_init()

On Wed, Oct 22, 2014 at 10:12 PM, David Miller <davem@...emloft.net> wrote:
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Date: Wed, 22 Oct 2014 21:50:06 +0200
>
>> On Wed, Oct 22, 2014 at 9:34 PM, David Miller <davem@...emloft.net> wrote:
>>> From: Geert Uytterhoeven <geert@...ux-m68k.org>
>>> Date: Wed, 22 Oct 2014 09:39:41 +0200
>>>
>>>> drivers/net/ethernet/apm/xgene/xgene_enet_sgmac.c: In function ‘xgene_enet_ecc_init’:
>>>> drivers/net/ethernet/apm/xgene/xgene_enet_sgmac.c:126: warning: ‘data’ may be used uninitialized in this function
>>>>
>>>> Depending on the arbitrary value on the stack, the loop may terminate
>>>> too early, and cause a bogus -ENODEV failure.
>>>>
>>>> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>>>> ---
>>>> v2: Rewrite the loop instead of pre-initializing data.
>>>
>>> I hate to be a pest, but like the other patch of your's I think
>>> a do { } while() works best here because the intent is clearly
>>> to run the loop at least once, right?
>>
>> I wanted to avoid checking for "data != ~0U" twice: once to abort the loop,
>> and once to check if a timeout happened.
>
> Hmmm:
>
>         do {
>                 usleep_range(...);
>                 data = ...();
>                 if (data == ~0)
>                         return 0;
>         } while (++i < 10);
>
>         netdev_err(...);
>         return -ENODEV;
>
> Why would you have to check data twice?



-- 
Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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