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

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Message-ID: <20090721160436.GD4352@dtor-d630.eng.vmware.com>
Date:	Tue, 21 Jul 2009 09:04:37 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	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, tglx@...utronix.de,
	David Brownell <david-b@...bell.net>
Subject: Re: Threaded interrupts for synaptic touchscreen in HTC dream

On Tue, Jul 21, 2009 at 01:49:33PM +0100, Mark Brown wrote:
> On Tue, Jul 21, 2009 at 06:00:07PM +0530, Trilok Soni wrote:
> 
> > Hopefully, this thread can give all details about threaded irq discussion.
> 
> > http://lkml.org/lkml/2009/2/27/255
> 
> Yes, I'm aware of that - I read it at the time.  It seemed to peter out
> without any satisfactory solution, unfortunately.  There's two separate
> issues here:
> 
>  - Ordinary devices on interrupt driven or slow buses like I2C.  These
>    need something along the lines of request_threaded_irq() that's allows
>    them to schedule the main IRQ handler outside hardirq context so
>    that they can interact with the device.  They need to do something in
>    hardirq context to disable the interrupt if it's level triggered but
>    most of the time the only option they've got is to disable the IRQ
>    and reenable it when the worker thread is done.  This is the issue
>    here.
> 
>    My immediate thought when I noticed this was that we should probably
>    fix request_threaded_irq() so that it's useful for them; I'd been
>    intending to do some digging and try to understand why it is
>    currently implemented as it is.
> 
>  - Multi-function devices like the twl4030 which have an interrupt
>    controller on them and would like to expose that interrupt controller
>    via the generic IRQ subsystem.  This was a large part of the
>    discussion in the thread above is a much trickier problem.
> 
> I've added the folks from Samsung posting the MELFAS MCS-5000 driver to
> the thread since they're running into the same issue.
> 

Let's also add Thomas and David since I believe they worked on the
feature.

>From my part I would like to have the threaded IRQ available to all
drivers since it seens to be hanlding driver shutdown cleanly and
without races which is a big plus for me since very few drivers get it
right.

-- 
Dmitry
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