linux-kernel - Re: [PATCH 2/2] gpio: davinci: Remove gpio2regs function to accommodate multi instances

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Date:   Wed, 11 Jan 2017 18:10:46 +0530
From:   Keerthy <j-keerthy@...com>
To:     Linus Walleij <linus.walleij@...aro.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Tero Kristo <t-kristo@...com>
Subject: Re: [PATCH 2/2] gpio: davinci: Remove gpio2regs function to
 accommodate multi instances



On Wednesday 11 January 2017 04:34 PM, Linus Walleij wrote:
> On Wed, Jan 4, 2017 at 9:26 AM, Keerthy <j-keerthy@...com> wrote:
>
>> gpio2regs is written making an assumption that driver supports only
>> one instance of gpio controller. Removing this and adding a generic
>> array so as to support multiple instances of gpio controllers.
>>
>> Signed-off-by: Keerthy <j-keerthy@...com>
>
>> -               regs = gpio2regs(base);
>> +               regs = gpio_base + offset_array[i];
>
> I understand this.
>
>> -       struct davinci_gpio_regs __iomem *g = gpio2regs(hw);
>> +       struct davinci_gpio_controller *chips =
>> +                               (struct davinci_gpio_controller *)d->host_data;
>> +       struct davinci_gpio_regs __iomem *g = chips[hw / 32].regs;
>
> And this, if each instans has 32 GPIOs.
>
>> -               g = gpio2regs(0);
>> +               g = chips[0].regs;
>
> Also makes sense.
>
>> -               g = gpio2regs(gpio);
>> +               g = chips[bank / 2].regs;
>
> But what is this? I don't understand that /2 at all. Please insert a
> comment explaining it so I can figure it out. Are there two banks
> per instance?

Yes! There are register sets for 32 GPIOs. 2 banks of 16 GPIOs are 
covered by each set of registers hence /2. Shall i add a comment and 
send this patch alone separately?


>
> Yours,
> Linus Walleij
>