linux-kernel - Re: [PATCH v2 2/5] gpio: pca953x: add register definitions for pcal6524 and fix address calculation

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Date:   Tue, 10 Apr 2018 17:41:14 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Kumar Gala <galak@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com
Subject: Re: [PATCH v2 2/5] gpio: pca953x: add register definitions for
 pcal6524 and fix address calculation

On Wed, Apr 4, 2018 at 10:00 PM, H. Nikolaus Schaller <hns@...delico.com> wrote:
> PCAL chips ("L" seems to stand for "latched") have additional
> registers starting at address 0x40 to control the latches,
> interrupt mask, pull-up and pull down etc.
>
> The constants are so far defined in a way that they fit for
> the pcal9555a when shifted by the number of banks, i.e. multiplied
> by 2.
>
> Now the pcal6524 has 3 banks which means the relative offset
> must be multiplied by 4 which gives a wrong result if not done
> carefully, since the base offset is already included in the offset.
>
> For the basic registers shared with all pca93xx/tca64xx chips
> there is no such offset.
>
> Therefore, we add code to adjust the register number for exended
> registers in this case.
>
> And we add additional register offset constants (not yet used by
> the driver code) which are specific to the pcal6524.

> -#define PCAL953X_IN_LATCH      34
> -#define PCAL953X_INT_MASK      37
> -#define PCAL953X_INT_STAT      38

I prefer either to change first all the rest to be 2 digit hex values
first, or leave decimal in this patch.

> +#define PCAL953X_OUT_STRENGTH  0x20
> +#define PCAL953X_IN_LATCH      0x22
> +#define PCAL953X_PULL_EN       0x23
> +#define PCAL953X_PULL_SEL      0x24
> +#define PCAL953X_INT_MASK      0x25
> +#define PCAL953X_INT_STAT      0x26
> +#define PCAL953X_OUT_CONF      0x27
> +
> +#define PCAL6524_INT_EDGE      0x28
> +#define PCAL6524_INT_CLR       0x2a
> +#define PCAL6524_IN_STATUS     0x2b
> +#define PCAL6524_OUT_INDCONF   0x2c
> +#define PCAL6524_DEBOUNCE      0x2d

> +       /* adjust register address for pcal6524 */
> +       if (reg >= PCAL953X_OUT_STRENGTH)
> +               reg -= PCAL953X_OUT_STRENGTH >> 1;

I don't like this condition. Can we avoid relying on the register
offset in regard to some flag / compatible string / etc?

> +       /* adjust register address for pcal6524 */
> +       if (reg >= PCAL953X_OUT_STRENGTH)
> +               reg -= PCAL953X_OUT_STRENGTH >> 1;

Ditto.

-- 
With Best Regards,
Andy Shevchenko