linux-kernel - Re: [PATCH v3 1/5] drivers: provide devm_platform_get_and_ioremap

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Message-ID: <CAMuHMdVK0Gpw6A=CfF+5nw4hHz9UCtSoXwF9_UThAK4E+mQBWg@mail.gmail.com>
Date:   Tue, 17 Mar 2020 20:35:16 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Dejin Zheng <zhengdejin5@...il.com>,
        "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>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Thierry Reding <treding@...dia.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Winkler, Tomas" <tomas.winkler@...el.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        USB list <linux-usb@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/5] drivers: provide devm_platform_get_and_ioremap_resource()

Hi Greg,

On Tue, Mar 17, 2020 at 8:20 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> On Sun, Mar 15, 2020 at 10:05:21PM +0800, Dejin Zheng 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.
> >
> > Suggested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > Suggested-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
> > Signed-off-by: Dejin Zheng <zhengdejin5@...il.com>
> > ---
> > v2 -> v3:
> >       - rename the function to
> >         devm_platform_get_and_ioremap_resource() by Sergei's suggestion.
> >       - make the last parameter res as optional by Geert's suggestion.
> >
> > v1 -> v2:
> >       - No change.
> >
> >  drivers/base/platform.c         | 22 ++++++++++++++++++++++
> >  include/linux/platform_device.h |  3 +++
> >  2 files changed, 25 insertions(+)
> >
> > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > index 7fa654f1288b..9f6a78f79235 100644
> > --- a/drivers/base/platform.c
> > +++ b/drivers/base/platform.c
> > @@ -62,6 +62,28 @@ struct resource *platform_get_resource(struct platform_device *dev,
> >  EXPORT_SYMBOL_GPL(platform_get_resource);
> >
> >  #ifdef CONFIG_HAS_IOMEM
> > +/**
> > + * devm_platform_get_and_ioremap_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_get_and_ioremap_resource(struct platform_device *pdev,
> > +                             unsigned int index, struct resource **res)
> > +{
> > +     struct resource *r;
> > +
> > +     r = platform_get_resource(pdev, IORESOURCE_MEM, index);
> > +     if (res)
> > +             *res = r;
>
> What happens if that call fails?  Shouldn't that be checked?

Then devm_ioremap_resource() will print an error message, and return
an error.
It's designed to be pipelined that way, so you have to check for an error
only once.

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