linux-kernel - Re: [PATCH V4 04/10] dt-bindings: timestamp: Add nvidia,gpio-controller

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Date:   Thu, 23 Mar 2023 09:36:16 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Dipen Patel <dipenp@...dia.com>
Cc:     thierry.reding@...il.com, jonathanh@...dia.com,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-doc@...r.kernel.org, robh+dt@...nel.org,
        timestamp@...ts.linux.dev, krzysztof.kozlowski+dt@...aro.org,
        brgl@...ev.pl, corbet@....net, gregkh@...uxfoundation.org
Subject: Re: [PATCH V4 04/10] dt-bindings: timestamp: Add nvidia,gpio-controller

On Thu, Mar 23, 2023 at 2:29 AM Dipen Patel <dipenp@...dia.com> wrote:

> Introducing nvidia,gpio-controller property from Tegra234 SoCs onwards.
> This is done to help below case.
>
> Without this property code would look like:
> if (of_device_is_compatible(dev->of_node, "nvidia,tegra194-gte-aon"))
>         hte_dev->c = gpiochip_find("tegra194-gpio-aon",
>                                    tegra_get_gpiochip_from_name);
> else if (of_device_is_compatible(dev->of_node, "nvidia,tegra234-gte-aon"))
>         hte_dev->c = gpiochip_find("tegra234-gpio-aon",
>                                    tegra_get_gpiochip_from_name);
> else
>         return -ENODEV;
>
> This means for every future addition of the compatible string, if else
> condition statements have to be expanded.
>
> With the property:
> gpio_ctrl = of_parse_phandle(dev->of_node, "nvidia,gpio-controller", 0);
> ....
> hte_dev->c = gpiochip_find(gpio_ctrl, tegra_get_gpiochip_from_of_node);
>
> This simplifies the code significantly. The introdunction of this
> property/binding does not break existing Tegra194 provider driver.
>
> Signed-off-by: Dipen Patel <dipenp@...dia.com>

It is fair to assume that other operating systems will need this too
so I interpret the commit message as an example of the issues
faced by anyone making a driver for this HW.
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij