From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Robert Richter <robert.richter@caviumnetworks.com>,
        Tomasz Nowicki <tomasz.nowicki@linaro.org>, linux-mips@linux-mips.org,
        David Daney <david.daney@cavium.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
        David Daney <ddaney.cavm@gmail.com>,
        Sunil Goutham <sgoutham@cavium.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH 2/2] net, thunder, bgx: Add support for ACPI binding.
Date: Sat, 08 Aug 2015 13:26:23 +0200
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On Friday 07 August 2015 12:43:20 Robert Richter wrote:
> 
> I would not pollute bgx_probe() with acpi and dt specifics, and instead
> keep bgx_init_phy(). The typical design pattern for this is:
> 
> static int bgx_init_phy(struct bgx *bgx)
> {
> #ifdef CONFIG_ACPI
>         if (!acpi_disabled)
>                 return bgx_init_acpi_phy(bgx);
> #endif
>         return bgx_init_of_phy(bgx);
> }
> 
> This adds acpi runtime detection (acpi=no), does not call dt code in
> case of acpi, and saves the #else for bgx_init_acpi_phy().
> 

What you should really do is to use the same function for both,
using the generic device properties API. If that is not possible,
explain in a comment why not.

Aside from that, if you do have to use compile-time conditionals,
use 'if (IS_ENABLED(CONFIG_ACPI) && !acpi_disabled)' instead of
#ifdef, for readability. The compiler will produce the same binary,
but also give helpful warnings about incorrect code that you don't
get with #ifdef.

	Arnd

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