linux-kernel - Re: [RFC] timers, pointers to functions and type safety

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Message-Id: <200612022243.58348.zippel@linux-m68k.org>
Date:	Sat, 2 Dec 2006 22:43:58 +0100
From:	Roman Zippel <zippel@...ux-m68k.org>
To:	Al Viro <viro@....linux.org.uk>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Matthew Wilcox <matthew@....cx>,
	Linus Torvalds <torvalds@...l.org>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] timers, pointers to functions and type safety

Hi,

On Saturday 02 December 2006 19:40, Al Viro wrote:

> RTFPosting.  It might be void *, but it's set via SETUP_TIMER which
> does type checks before casting to void *.
>
> IOW, I don't want _any_ typecasts/container_of necessary in the code.
>
> Sane variant is
>
> void foo_timer(struct net_device *dev)
> {
> 	...
> }
>
> 	struct foo_dev *p = netdev_priv(dev);
> 	SETUP_TIMER(&p->timer, foo_timer, dev);
>
> etc.
>
> With warning generated if foo_timer(dev) would not be type safe.  Without
> typecasts.  Without container_of().  Without any bleeding cruft at all.

You need some more magic macros to access/modify the data field.
Your SETUP_TIMER macro only protects the simple cases, which are easy anyway, 
in this case I prefer the space savings container_of can give us.

bye, Roman
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