linux-kernel - Re: [PATCH 1/3] net: phy: prevent linking breakage

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Message-Id: <201305272320.08296.f.fainelli@gmail.com>
Date:	Tue, 28 May 2013 00:20:05 +0200
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
	Shawn Guo <shawn.guo@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Sascha Hauer <kernel@...gutronix.de>,
	linux-kernel@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>
Subject: Re: [PATCH 1/3] net: phy: prevent linking breakage

Hi,

Le 27 mai 2013 19:38, "Alexandre Belloni" <alexandre.belloni@...e-
electrons.com> a écrit :

[snip]

> >> +/*
> >> + *  phy_register_fixup{,_for_uid,_for_id} are called from arch/ so this 
won't
> >> + *  work unless phylib is compiled in the kernel.
> >> + *  Defining stubs allows to prevent linking errors.
> >> + */
> >> +#ifdef CONFIG_PHYLIB
> >>  int phy_register_fixup(const char *bus_id, u32 phy_uid, u32 phy_uid_mask,
> >>              int (*run)(struct phy_device *));
> >>  int phy_register_fixup_for_id(const char *bus_id,
> >>              int (*run)(struct phy_device *));
> >>  int phy_register_fixup_for_uid(u32 phy_uid, u32 phy_uid_mask,
> >>              int (*run)(struct phy_device *));
> >> +#else
> >> +#define phy_register_fixup(a, b, c, d) do { } while (0)
> >> +#define phy_register_fixup_for_id(a, b) do { } while (0)
> >> +#define phy_register_fixup_for_uid(a, b, c) do { } while (0)
> > Use static inline functions here. This breaks if someone does result
> > checking on the functions which then expands to ret = do {} while (0);
> > Also we still have
> Right, I tried that first but forgot static so I had issues with
> redefinition of the functions. I even played with __weak at some point...

You might even want to make these static inlines as mentionned earlier, and 
return something like -ENOTSUPP so that someone using these in board code and 
wondering why they do not work gets a chance to enable CONIFG_PHYLIB.
--
Florian
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