linux-kernel - Re: [PATCH 2/2] net, thunder, bgx: Add support for ACPI binding.

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Date:	Sat, 08 Aug 2015 13:26:23 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Robert Richter <robert.richter@...iumnetworks.com>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	linux-mips@...ux-mips.org, David Daney <david.daney@...ium.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, David Daney <ddaney.cavm@...il.com>,
	Sunil Goutham <sgoutham@...ium.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 2/2] net, thunder, bgx: Add support for ACPI binding.

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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