linux-kernel - 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 22:23:36 +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 9:26 PM Colin Foster
<colin.foster@...advantage.com> wrote:
>
> Several ocelot-related modules are designed for MMIO / regmaps. As such,
> they often use a combination of devm_platform_get_and_ioremap_resource and
> devm_regmap_init_mmio.
>
> Operating in an MFD might be different, in that it could be memory mapped,
> or it could be SPI, I2C... In these cases a fallback to use IORESOURCE_REG
> instead of IORESOURCE_MEM becomes necessary.
>
> When this happens, there's redundant logic that needs to be implemented in
> every driver. In order to avoid this redundancy, utilize a single function
> that, if the MFD scenario is enabled, will perform this fallback logic.

...

> +       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?

  regs = devm_platform_get_and_ioremap_resource();
  if (res) {
    if (IS_ERR(regs))
      return ERR_CAST();
   return ...
  }

> +               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);

-- 
With Best Regards,
Andy Shevchenko