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

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Date:	Wed, 22 Jul 2009 21:43:22 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	David Brownell <david-b@...bell.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.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, Daniel Ribeiro <drwyrm@...il.com>
Subject: Re: Threaded interrupts for synaptic touchscreen in HTC dream

On Wed, Jul 22, 2009 at 11:04:33PM +0200, Thomas Gleixner wrote:
> 
> Any more ?
> 

Can we also have something like below by any chance?

-- 
Dmitry

genirq: provide dummy hard irq handler for threaded interrupts

From: Dmitry Torokhov <dmitry.torokhov@...il.com>

Quite often drivers using threaded interrupts don't do anything
in the hard IRQ portion of their interrupt handler; everything
is offloaded to the threaded half. Instead of having every driver
implement a stub have one ready in the IRQ core.

Signed-off-by: Dmitry Torokhov <dtor@...l.ru>
---

 kernel/irq/manage.c |   22 ++++++++++++++++++----
 1 files changed, 18 insertions(+), 4 deletions(-)


diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 50da676..cdc52f6 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -695,6 +695,15 @@ out_thread:
 	return ret;
 }
 
+/*
+ * Default hardirq handler for threaded irqs that is used when
+ * driver did not provide its own implementation.
+ */
+static irqreturn_t dummy_hardirq_handler(int irq, void *dev_id)
+{
+	return IRQ_WAKE_THREAD;
+}
+
 /**
  *	setup_irq - setup an interrupt
  *	@irq: Interrupt line to setup
@@ -837,8 +846,11 @@ EXPORT_SYMBOL(free_irq);
  *	request_threaded_irq - allocate an interrupt line
  *	@irq: Interrupt line to allocate
  *	@handler: Function to be called when the IRQ occurs.
- *		  Primary handler for threaded interrupts
- *	@thread_fn: Function called from the irq handler thread
+ *		  Primary handler for threaded interrupts.
+ *		  May be NULL, in which case a dummy interrupt
+ *		  handler is used that simply returns
+ *		  IRQ_WAKE_THREAD
+ *	@thread_fn: Function called from the irq handler thread.
  *		    If NULL, no irq thread is created
  *	@irqflags: Interrupt type flags
  *	@devname: An ascii name for the claiming device
@@ -917,14 +929,16 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
 
 	if (desc->status & IRQ_NOREQUEST)
 		return -EINVAL;
-	if (!handler)
+
+	if (!handler && !thread_fn) {
 		return -EINVAL;
+	}
 
 	action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
 	if (!action)
 		return -ENOMEM;
 
-	action->handler = handler;
+	action->handler = handler ?: dummy_hardirq_handler;
 	action->thread_fn = thread_fn;
 	action->flags = irqflags;
 	action->name = devname;
--
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