linux-kernel - Re: [PATCH v2 1/4] drivers: provide devm_platform_ioremap_and_get

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Date:   Sun, 15 Mar 2020 10:47:59 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Dejin Zheng <zhengdejin5@...il.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Minas Harutyunyan <hminas@...opsys.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Arnd Bergmann <arnd@...db.de>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Thierry Reding <treding@...dia.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Hans de Goede <hdegoede@...hat.com>,
        USB list <linux-usb@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] drivers: provide devm_platform_ioremap_and_get_resource()

Hi Dejin,

On Sat, Mar 14, 2020 at 6:26 AM Dejin Zheng <zhengdejin5@...il.com> wrote:
> Since commit "drivers: provide devm_platform_ioremap_resource()",
> It was wrap platform_get_resource() and devm_ioremap_resource() as
> single helper devm_platform_ioremap_resource(). but now, many drivers
> still used platform_get_resource() and devm_ioremap_resource()
> together in the kernel tree. The reason can not be replaced is they
> still need use the resource variables obtained by platform_get_resource().
> so provide this helper.
>
> Signed-off-by: Dejin Zheng <zhengdejin5@...il.com>

Thanks for your patch!

> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -62,6 +62,24 @@ struct resource *platform_get_resource(struct platform_device *dev,
>  EXPORT_SYMBOL_GPL(platform_get_resource);
>
>  #ifdef CONFIG_HAS_IOMEM
> +/**
> + * devm_platform_ioremap_and_get_resource - call devm_ioremap_resource() for a
> + *                                         platform device and get resource
> + *
> + * @pdev: platform device to use both for memory resource lookup as well as
> + *        resource management
> + * @index: resource index
> + * @res: get the resource
> + */
> +void __iomem *
> +devm_platform_ioremap_and_get_resource(struct platform_device *pdev,
> +                               unsigned int index, struct resource **res)
> +{
> +       *res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> +       return devm_ioremap_resource(&pdev->dev, *res);
> +}
> +EXPORT_SYMBOL_GPL(devm_platform_ioremap_and_get_resource);

As this duplicates most of the implementation of
devm_platform_ioremap_resource(),
I think it would be better to make res optional:

    void __iomem *
    devm_platform_ioremap_and_get_resource(struct platform_device *pdev,
                                           unsigned int index, struct
resource **resp)
    {
            struct resource **res;

            res = platform_get_resource(pdev, IORESOURCE_MEM, index);
            if (resp)
                    *resp = res;
            return devm_ioremap_resource(&pdev->dev, *res);
    }

And implement devm_platform_ioremap_resource() by calling
devm_platform_ioremap_and_get_resource() with resp = NULL.
Whether the best way to do that is as an exported functions, or as an
inlined function, is to be seen (measure impact on kernel size).

> +
>  /**
>   * devm_platform_ioremap_resource - call devm_ioremap_resource() for a platform
>   *                                 device
> diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
> index 276a03c24691..5fd1977e3eaf 100644
> --- a/include/linux/platform_device.h
> +++ b/include/linux/platform_device.h
> @@ -55,6 +55,9 @@ extern struct device *
>  platform_find_device_by_driver(struct device *start,
>                                const struct device_driver *drv);
>  extern void __iomem *
> +devm_platform_ioremap_and_get_resource(struct platform_device *pdev,
> +                               unsigned int index, struct resource **res);
> +extern void __iomem *
>  devm_platform_ioremap_resource(struct platform_device *pdev,
>                                unsigned int index);
>  extern void __iomem *

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds