Date: Fri, 6 Aug 2010 15:46:05 +0100
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Linus Walleij <linus.ml.walleij@gmail.com>,
	Vitaly Wool <vitalywool@gmail.com>,
	Kalle Valo <kalle.valo@iki.fi>,
	Pandita Vikram <vikram.pandita@ti.com>,
	Nicolas Pitre <nico@fluxnic.net>,
	Tony Lindgren <tony@atomide.com>,
	linux-wireless@vger.kernel.org,
	Roger Quadros <roger.quadros@nokia.com>,
	linux-mmc@vger.kernel.org, San Mehat <san@google.com>,
	Chikkature Rajashekar Madhusudhan <madhu.cr@ti.com>,
	Luciano Coelho <luciano.coelho@nokia.com>,
	linux-omap@vger.kernel.org, akpm@linux-foundation.org,
	linux-arm-kernel@lists.infradead.org, Ido Yariv <ido@wizery.com>
Subject: Re: [PATCH v2 03/20] mmc: support embedded data field in mmc_host
Message-ID: <20100806144605.GA21015@n2100.arm.linux.org.uk>
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On Fri, Aug 06, 2010 at 01:02:24PM +0300, Ohad Ben-Cohen wrote:
> We have Russell's suggestion which is nice and simple, but it has the
> 1 device limitation.

You could make it generic by doing something like this:

#define set_device_data(name, type, index, data)			\
 ({									\
    extern void __set_device_data(const char *, int, void *, size_t);	\
    BUILD_BUG_ON(!__same_type(type, *data));				\
    __set_device_data(name ":" #type, index, data, sizeof(type));	\
 })

#define get_device_data(name, type, index) ({				\
  extern void *__get_device_data(const char *, int);			\
  type *__ptr = __get_device_data(name ":" #type, index);		\
  __ptr; })

And now we have something that takes a string and index to use as a lookup
key in some kind of list - and it's typesafe (because the lookup key is
dependent on the stringified type.)

But... at this point I feel that we're getting too complicated, and will
get shouted at to use something like DT which already solves this problem.