linux-kernel - Re: [PATCH v4 11/18] asm-generic/io.h: implement pci_remap_cfgspace using ioremap

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Message-ID: <20210407210317.GB16198@willie-the-truck>
Date:   Wed, 7 Apr 2021 22:03:17 +0100
From:   Will Deacon <will@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Hector Martin <marcan@...can.st>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Marc Zyngier <maz@...nel.org>, Rob Herring <robh@...nel.org>,
        Arnd Bergmann <arnd@...nel.org>,
        Olof Johansson <olof@...om.net>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        Tony Lindgren <tony@...mide.com>,
        Mohamed Mediouni <mohamed.mediouni@...amail.com>,
        Stan Skowronek <stan@...ellium.com>,
        Alexander Graf <graf@...zon.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Hellwig <hch@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Documentation List <linux-doc@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 11/18] asm-generic/io.h: implement pci_remap_cfgspace
 using ioremap_np

On Wed, Apr 07, 2021 at 04:27:42PM +0300, Andy Shevchenko wrote:
> On Fri, Apr 2, 2021 at 12:07 PM Hector Martin <marcan@...can.st> wrote:
> >
> > Now that we have ioremap_np(), we can make pci_remap_cfgspace() default
> > to it, falling back to ioremap() on platforms where it is not available.
> >
> > Remove the arm64 implementation, since that is now redundant. Future
> > cleanups should be able to do the same for other arches, and eventually
> > make the generic pci_remap_cfgspace() unconditional.
> 
> ...
> 
> > +       void __iomem *ret = ioremap_np(offset, size);
> > +
> > +       if (!ret)
> > +               ret = ioremap(offset, size);
> > +
> > +       return ret;
> 
> Usually negative conditions are worse for cognitive functions of human beings.
> (On top of that some patterns are applied)
> 
> I would rewrite above as
> 
> void __iomem *ret;
> 
> ret = ioremap_np(offset, size);
> if (ret)
>   return ret;
> 
> return ioremap(offset, size);

Looks like it might be one of those rare occasions where the GCC ternary if
extension thingy comes in handy:

	return ioremap_np(offset, size) ?: ioremap(offset, size);

but however it's done, the logic looks good to me and thanks Hector for
updating this:

Acked-by: Will Deacon <will@...nel.org>

Will