netdev - Re: [PATCH v12 net-next 1/9] mfd: ocelot: add helper to get regmap from a resource

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Date:   Fri, 1 Jul 2022 22:41:43 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Colin Foster <colin.foster@...advantage.com>
Cc:     devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Lee Jones <lee.jones@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Wolfram Sang <wsa@...nel.org>,
        Terry Bowman <terry.bowman@....com>,
        katie.morris@...advantage.com
Subject: Re: [PATCH v12 net-next 1/9] mfd: ocelot: add helper to get regmap
 from a resource

On Fri, Jul 1, 2022 at 10:35 PM Colin Foster
<colin.foster@...advantage.com> wrote:
> On Fri, Jul 01, 2022 at 10:23:36PM +0200, Andy Shevchenko wrote:
> > On Fri, Jul 1, 2022 at 9:26 PM Colin Foster
> > <colin.foster@...advantage.com> wrote:

...

> > > +       res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> > > +       if (res) {
> > > +               regs = devm_ioremap_resource(dev, res);
> > > +               if (IS_ERR(regs))
> > > +                       return ERR_CAST(regs);
> >
> > Why can't it be devm_platform_get_and_ioremap_resource() here?
>
> It can... but it invokes prints of "invalid resource" during
> initialization.
>
> Here it was implied that I should break the function call out:
> https://patchwork.kernel.org/project/netdevbpf/patch/20220628081709.829811-2-colin.foster@in-advantage.com/#24917551

Perhaps a comment in the code, so nobody will try to optimize this in
the future.

> > > +               return devm_regmap_init_mmio(dev, regs, config);
> > > +       }

...

> > > +       return (map) ? map : ERR_PTR(-ENOENT);
> >
> > Too many parentheses.
> >
> > Also you may use short form of ternary operator:
> >
> >        return map ?: ERR_PTR(-ENOENT);
>
> Agreed, and I didn't know about that operator. When Vladimir suggested
> it I thought it was a typo. I should've known better.

It's easy to remember by thinking of

"X ?: Y" as "X _or_ Y".

-- 
With Best Regards,
Andy Shevchenko