linux-kernel - Re: [PATCH v7 3/3] gpio: pca953x: fix address calculation for pcal6524

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Message-ID: <CACRpkdYfjqRaUnYXhksXANbgyn++nUAda4D1prawGU1vZ06wQg@mail.gmail.com>
Date:   Wed, 23 May 2018 13:48:38 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Kumar Gala <galak@...eaurora.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Alexandre Courbot <gnurou@...il.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com
Subject: Re: [PATCH v7 3/3] gpio: pca953x: fix address calculation for pcal6524

On Thu, May 17, 2018 at 6:59 AM, H. Nikolaus Schaller <hns@...delico.com> wrote:

> The register constants are so far defined in a way that they fit
> for the pcal9555a when shifted by the number of banks, i.e. are
> multiplied by 2 in the accessor function.
>
> Now, the pcal6524 has 3 banks which means the relative offset
> is multiplied by 4 for the standard registers.
>
> Simply applying the bit shift to the extended registers gives
> a wrong result, since the base offset is already included in
> the offset.
>
> Therefore, we have to add code to the 24 bit accessor functions
> that adjusts the register number for these exended registers.
>
> The formula finally used was developed and proposed by
> Andy Shevchenko <andy.shevchenko@...il.com>.
>
> Suggested-by: Andy Shevchenko <andy.shevchenko@...il.com>
> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>

Patch applied.

Yours,
Linus Walleij