linux-kernel - Re: Threaded interrupts for synaptic touchscreen in HTC dream

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Date:	Wed, 22 Jul 2009 10:04:10 -0700
From:	David Brownell <david-b@...bell.net>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Trilok Soni <soni.trilok@...il.com>,
	Pavel Machek <pavel@....cz>,
	"Arve Hj?nnev?g" <arve@...roid.com>,
	kernel list <linux-kernel@...r.kernel.org>,
	Brian Swetland <swetland@...gle.com>,
	linux-input@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	linux-i2c@...r.kernel.org,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	m.szyprowski@...sung.com, t.fujak@...sung.com,
	kyungmin.park@...sung.com, Peter Zijlstra <peterz@...radead.org>,
	Daniel Ribeiro <drwyrm@...il.com>
Subject: Re: Threaded interrupts for synaptic touchscreen in HTC dream

On Wednesday 22 July 2009, Mark Brown wrote:
> Yes, I think that'll be required for users like gpiolib.  If someone's
> done something like have a button implemented by attaching switch to a
> GPIO input on for something like jack detect on an audio CODEC or a wake
> source for a PMIC then we've got generic code that expects to just take
> a gpio/irq and interact with it.

Is there a problem with how it works now?  GPIO calls come in
sleeping (e.g. over I2C or SPI) and non-sleeping (classic SoC
GPIOs) varieties.  And it's not gpiolib which would handle any
IRQ support ... it's the driver for the GPIO chip, which would
expose both irq_chip and gpio_chip facets.  (Just like classic
SoC GPIO drivers.)

So if a handler uses only non-sleeping calls, it needs at most
minor tweaks to make sure it can be used from a threaded context.

If it uses sleeping calls, it already has to arrange that it
runs in a threaded context.  

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