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Date: Thu, 11 Oct 2012 17:37:15 +0200
Message-ID: <CACRpkdbRiwedVsvYo-8b5T0TVsUt69dFFkRpNwwGUPSuUYYLoQ@mail.gmail.com>
Subject: Re: [RFC PATCH 02/06] input/rmi4: Core files
From: Linus Walleij <linus.walleij@linaro.org>
To: Christopher Heiny <Cheiny@synaptics.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Jean Delvare <khali@linux-fr.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Linux Input <linux-input@vger.kernel.org>,
        Allie Xiong <axiong@synaptics.com>, Vivian Ly <vly@synaptics.com>,
        Daniel Rosenberg <daniel.rosenberg@synaptics.com>,
        Joerie de Gram <j.de.gram@gmail.com>,
        Wolfram Sang <w.sang@pengutronix.de>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Linus Walleij <linus.walleij@stericsson.com>,
        Naveen Kumar Gaddipati <naveen.gaddipati@stericsson.com>,
        Alexandra Chin <alexandra.chin@tw.synaptics.com>
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On Thu, Oct 11, 2012 at 6:15 AM, Christopher Heiny <Cheiny@synaptics.com> wrote:
> On Thursday, October 11, 2012 02:21:53 AM I wrote:

>> > +union pdt_properties {
>> > +       struct {
>> > +               u8 reserved_1:6;
>> > +               u8 has_bsr:1;
>> > +               u8 reserved_2:1;
>> > +       } __attribute__((__packed__));
>> > +       u8 regs[1];
>>
>> I don't understand what this union is trying to achieve.
>>
>> regs[1] does not look right considering what you're trying to
>> achieve. Since the above fields require a regs[2] (9 bits!)
>> to be stored. Maybe write out what you're trying to do here
>> so I can understand it? (If everyone else in the world gets
>> it immediately, it's maybe me that need fixing instead...)
>>
>> Apart from these remarks it's looking real nice now!
>
> I only count 8 bits there, unless there's something about
> packing I'm not aware of.  Is there something else you
> found confusing about the union?

I just did bad maths, too many figured in the struct...

But consider Dmitry's suggestion that you might get rid
of this unionizing.

Yours,
Linus Walleij
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