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Commit f38bc926 authored by Lars-Peter Clausen's avatar Lars-Peter Clausen Committed by Jonathan Cameron
Browse files

staging:iio:sysfs-trigger: Use irq_work to properly active trigger 



Since iio_trigger_poll() calls generic_handle_irq() it need to be called from
hardirq context. The sysfs trigger is kicked from userspace, so it is obviously
not possible to fulfill this requirement by calling iio_trigger_poll directly.
As a workaround commit 1f785681 ("staging:iio:trigger sysfs userspace trigger
rework.") added iio_trigger_poll_chained() which uses handle_nested_irq instead
of generic_handle_irq. This in itself is a hack and only works by chance.
handle_nested_irq is intended to be called from the threaded interrupt handler
of the parent IRQ. Using handle_nested_irq is also problematic since it will
only call the threaded handler of the IRQ. But quite a few IIO drivers rely on
their hardirq handler being called or undefined behaviour will occur.

This patch uses the irq_work framework to schedule the call to
iio_trigger_poll() from hardirq context, which fixes the issues described above.

Signed-off-by: default avatarLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent ed5514c9

drivers/staging/iio/trigger/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -21,6 +21,8 @@ config IIO_GPIO_TRIGGER 
config IIO_SYSFS_TRIGGER

	tristate "SYSFS trigger"

	depends on SYSFS

	depends on HAVE_IRQ_WORK

	select IRQ_WORK

	help

	  Provides support for using SYSFS entry as IIO triggers.

	  If unsure, say N (but it's safe to say "Y").

drivers/staging/iio/trigger/iio-trig-sysfs.c

+16 −1
Original line number Diff line number Diff line
@@ -10,12 +10,14 @@ 
#include <linux/platform_device.h>

#include <linux/slab.h>

#include <linux/list.h>

#include <linux/irq_work.h>



#include <linux/iio/iio.h>

#include <linux/iio/trigger.h>



struct iio_sysfs_trig {

	struct iio_trigger *trig;

	struct irq_work work;

	int id;

	struct list_head l;

};
@@ -89,11 +91,21 @@ static struct device iio_sysfs_trig_dev = { 
	.release = &iio_trigger_sysfs_release,

};



static void iio_sysfs_trigger_work(struct irq_work *work)

{

	struct iio_sysfs_trig *trig = container_of(work, struct iio_sysfs_trig,

							work);



	iio_trigger_poll(trig->trig, 0);

}



static ssize_t iio_sysfs_trigger_poll(struct device *dev,

		struct device_attribute *attr, const char *buf, size_t count)

{

	struct iio_trigger *trig = to_iio_trigger(dev);

	iio_trigger_poll_chained(trig, 0);

	struct iio_sysfs_trig *sysfs_trig = trig->private_data;



	irq_work_queue(&sysfs_trig->work);



	return count;

}
@@ -148,6 +160,9 @@ static int iio_sysfs_trigger_probe(int id) 
	t->trig->dev.groups = iio_sysfs_trigger_attr_groups;

	t->trig->ops = &iio_sysfs_trigger_ops;

	t->trig->dev.parent = &iio_sysfs_trig_dev;

	t->trig->private_data = t;



	init_irq_work(&t->work, iio_sysfs_trigger_work);



	ret = iio_trigger_register(t->trig);

	if (ret)