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

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Message-ID: <alpine.DEB.2.20.1707041153160.3346@hadrien>
Date:   Tue, 4 Jul 2017 11:53:56 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
cc:     Julia Lawall <julia.lawall@...6.fr>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>,
        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 Tue, 4 Jul 2017, Andy Shevchenko wrote:

> On Tue, Jul 4, 2017 at 12:11 PM, Julia Lawall <julia.lawall@...6.fr> wrote:
> > Here is a revised version (not a patch because it doesn't support all of
> > the various modes) and the results.  It doesn't return anything beyond
> > what was mentioned in previous mails.
> >
> > For the following code:
> >
> >         ret = i2c_smbus_read_word_data(chip->client, reg << 1);
> >         val[0] = (u16)ret & 0xFF;
> >         val[1] = (u16)ret >> 8;
> >
> > do we want to see:
> >
> > put_unaligned(val,i2c_smbus_read_word_data(chip->client, reg << 1));
>
> If and only if the type of the pointer is a byte type (u8 *, char *,
> or alike) _and_ we try to use it as a provider for 16-bit value (2
> bytes).

OK, the provider part seems to add more complexity than is worth putting
in the rule, so I will let the developer figure out what should be done.

thanks,
julia