linux-kernel - Re: [PATCH] coccinelle: api: detect unnecessary le16_to

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Message-ID: <CAHp75VeLV_ySCRN3B=MSoZdyrbXXqqEXrgC+hJCDoLLCJRComQ@mail.gmail.com>
Date:   Mon, 3 Jul 2017 20:33:53 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.co.uk>
Cc:     Julia Lawall <Julia.Lawall@...6.fr>,
        kernel-janitors@...r.kernel.org,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Michal Marek <mmarek@...e.com>, cocci@...teme.lip6.fr,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Bastien Nocera <hadess@...ess.net>,
        Stephen Just <stephenjust@...il.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Lv Zheng <lv.zheng@...el.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        devel@...ica.org,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] coccinelle: api: detect unnecessary le16_to_cpu

On Mon, Jul 3, 2017 at 8:14 PM, Sebastian Reichel
<sebastian.reichel@...labora.co.uk> wrote:
> Hi,
>
> On Mon, Jul 03, 2017 at 07:37:59PM +0300, Andy Shevchenko wrote:
>> On Mon, Jul 3, 2017 at 4:36 PM, Sebastian Reichel
>> <sebastian.reichel@...labora.co.uk> wrote:
>> > On Sat, Jul 01, 2017 at 09:28:10PM +0200, Julia Lawall wrote:
>>
>> >  * drivers/gpio/gpio-pca953x.c (line 190-192)
>>
>> It has double conversion there:
>> 1. LE CPU: Read as LE and converted to LE (no-op), so, just u16
>> 2. BE CPU: Read as BE and converted to LE, makes it __le16
>>
>> Looks like the conversion is not needed, only get_unaligned() is necessary.
>>
>> P.S. What about lines 244-245 there? I think they are no-op.
>> Interesting that those two parts were added in quite different
>> commits.
>
> val[0] = (u16)ret & 0xFF;
> val[1] = (u16)ret >> 8;
>
> looks like cpu_to_be16()?

cpu_to_le16(). No-op on LE CPU.

Perhaps they should be replaced by put_unaligned().

-- 
With Best Regards,
Andy Shevchenko