linux-kernel - [RFC patch 0/3] Support for irq chips on slow busses (i2c, spi)

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Message-Id: <20090813191535.945521006@linutronix.de>
Date:	Thu, 13 Aug 2009 19:40:35 -0000
From:	Thomas Gleixner <tglx@...utronix.de>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Trilok Soni <soni.trilok@...il.com>,
	Pavel Machek <pavel@....cz>,
	Brian Swetland <swetland@...gle.com>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	m.szyprowski@...sung.com, t.fujak@...sung.com,
	kyungmin.park@...sung.com, David Brownell <david-b@...bell.net>,
	Daniel Ribeiro <drwyrm@...il.com>, arve@...roid.com,
	Barry Song <21cnbao@...il.com>
Subject: [RFC patch 0/3] Support for irq chips on slow busses (i2c, spi)

The support for irq chips on slow busses eg. i2c, spi has been
discussed to great length several times. Most of the details can be
found in this thread: http://lkml.org/lkml/2009/7/21/266

The following patch series is a round up of the various patch snippets
sent out during the discussion and the ideas we agreed on.

There are some subtle differences to the initial test patches:

1) Instead of using a separate flow handler we allow to request the
one shot feature with a flag on request_irq and integrate the oneshot
feature into the existing level/edge handlers.

2) Instead of conditional locking which makes the patch smaller but
hides the already known fact that a device sits behind a slow irq chip
I implemented a set of separate management functions (see patch
2/3). The initial idea with the conditional locking can be found here:
http://lkml.org/lkml/2009/7/22/163

3) patch 3/3 implements a helper function which allows the
demultiplexing thread to call the demux handlers in its own thread
context with out creating a separate thread for each subdevice
interrupt. The device driver needs to request the interrupt via
request_nested_slowbus_irq() to prevent the creation of the extra
thread.

Please have a thorough look and hopefully a test ride on your
favourite slowbus irq chip implementation so we can get this into .32

Thanks,

	tglx

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