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>

diff --git a/drivers/staging/iio/trigger/Kconfig b/drivers/staging/iio/trigger/Kconfig
index b8abf5473ddc7413456dc95f1646b51a38f8c2df..7d3207559265c35085652be0a23b3942f5031171 100644 (file)
--- a/drivers/staging/iio/trigger/Kconfig
+++ b/drivers/staging/iio/trigger/Kconfig
@@ -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").

diff --git a/drivers/staging/iio/trigger/iio-trig-sysfs.c b/drivers/staging/iio/trigger/iio-trig-sysfs.c
index fee474648108e02d234b3e4523962e97ee4901bf..3bac97224bf4c8683e2f8ac6a180435bf1c0a5b5 100644 (file)
--- a/drivers/staging/iio/trigger/iio-trig-sysfs.c
+++ b/drivers/staging/iio/trigger/iio-trig-sysfs.c
@@ -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)