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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: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Lars-Peter Clausen 2012-09-06 10:05:00 +01:00 committed by Jonathan Cameron
parent ed5514c925
commit f38bc926d0
2 changed files with 18 additions and 1 deletions
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2
drivers/staging/iio/trigger/Kconfig
View File

@ -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").

17
drivers/staging/iio/trigger/iio-trig-sysfs.c
View File

@ -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)