Add "parent_trigger" sysfs attribute to iio trigger to be able
to set a parent to the current trigger.
Parent trigger edges or levels could be used to control current
trigger status for example to start, stop or reset it.
Introduce validate_trigger function in iio_trigger_ops which does
the same than validate_device but with a trigger as second parameter.
Driver must implement this function and add dev_attr_parent_trigger
in their trigger attribute group to be able to use parent trigger
feature.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxx>
version 3:
- try to provide better description of parent_trigger usages
version 2:
- add comment about parent trigger usage
- parent trigger attribute must be set the driver no more by IIO core
---
.../ABI/testing/sysfs-bus-iio-trigger-sysfs | 15 +++++
drivers/iio/industrialio-trigger.c | 69 ++++++++++++++++++++++
include/linux/iio/trigger.h | 7 ++-
3 files changed, 90 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-iio-trigger-sysfs b/Documentation/ABI/testing/sysfs-bus-iio-trigger-sysfs
index 04ac623..1e7fc40 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio-trigger-sysfs
+++ b/Documentation/ABI/testing/sysfs-bus-iio-trigger-sysfs
@@ -40,3 +40,18 @@ Description:
associated file, representing the id of the trigger that needs
to be removed. If the trigger can't be found, an invalid
argument message will be returned to the user.
+
+What: /sys/bus/iio/devices/triggerX/parent_trigger
+KernelVersion: 4.12
+Contact: linux-iio@xxxxxxxxxxxxxxx
+Description:
+ This attribute is used to set a trigger as parent for the
+ current trigger. If the trigger can't use the parent an
+ invalid argument message will be returned.
+ Parent trigger edges or levels could be used to control current
+ trigger. For example current trigger could be started on parent
+ rising edges or be enabled only when parent trigger level is
+ high.
+ Since there is many ways to use parent edges and levels to
+ control current trigger behavoir an additional custom sysfs
+ attribute may be needed to describe those control modes.
diff --git a/drivers/iio/industrialio-trigger.c b/drivers/iio/industrialio-trigger.c
index 978729f..9891fb2 100644
--- a/drivers/iio/industrialio-trigger.c
+++ b/drivers/iio/industrialio-trigger.c
@@ -58,6 +58,74 @@ static ssize_t iio_trigger_read_name(struct device *dev,
static DEVICE_ATTR(name, S_IRUGO, iio_trigger_read_name, NULL);
+/**
+ * iio_trigger_read_parent() - trigger consumer sysfs query parent trigger
+ * @dev: device associated with an industrial I/O trigger
+ * @attr: pointer to the device_attribute structure that
+ * is being processed
+ * @buf: buffer where the current trigger name will be printed into
+ *
+ * Return: a negative number on failure, the number of characters written
+ * on success or 0 if no trigger is available
+ */
+static ssize_t iio_trigger_read_parent(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct iio_trigger *trig = to_iio_trigger(dev);
+
+ if (trig->parent_trigger)
+ return sprintf(buf, "%s\n", trig->parent_trigger->name);
+
+ return 0;
+}
+
+static struct iio_trigger *iio_trigger_find_by_name(const char *name,
+ size_t len);
+
+/**
+ * iio_trigger_write_parent() - trigger consumer sysfs set parent trigger
+ * @dev: device associated with an industrial I/O trigger
+ * @attr: device attribute that is being processed
+ * @buf: string buffer that holds the name of the trigger
+ * @len: length of the trigger name held by buf
+ *
+ * Return: negative error code on failure or length of the buffer
+ * on success
+ */
+static ssize_t iio_trigger_write_parent(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf,
+ size_t len)
+{
+ struct iio_trigger *parent;
+ struct iio_trigger *child = to_iio_trigger(dev);
+ int ret;
+
+ if (!child->ops->validate_trigger)
+ return -EINVAL;
+
+ if (atomic_read(&child->use_count))
+ return -EBUSY;
+
+ parent = iio_trigger_find_by_name(buf, len);
+
+ if (parent == child->parent_trigger)
+ return len;
+
+ ret = child->ops->validate_trigger(child, parent);
+ if (ret)
+ return ret;
+
+ child->parent_trigger = parent;
+
+ return len;
+}
+
+DEVICE_ATTR(parent_trigger, S_IRUGO | S_IWUSR,
+ iio_trigger_read_parent, iio_trigger_write_parent);
+EXPORT_SYMBOL_GPL(dev_attr_parent_trigger);
+
static struct attribute *iio_trig_dev_attrs[] = {
&dev_attr_name.attr,
NULL,
@@ -440,6 +508,7 @@ static ssize_t iio_trigger_write_current(struct device *dev,
indio_dev->pollfunc_event);
iio_trigger_put(oldtrig);
}
+
if (indio_dev->trig) {
iio_trigger_get(indio_dev->trig);
if (indio_dev->modes & INDIO_EVENT_TRIGGERED)
diff --git a/include/linux/iio/trigger.h b/include/linux/iio/trigger.h
index ea08302..efa2983 100644
--- a/include/linux/iio/trigger.h
+++ b/include/linux/iio/trigger.h
@@ -20,6 +20,7 @@ struct iio_subirq {
struct iio_dev;
struct iio_trigger;
+extern struct device_attribute dev_attr_parent_trigger;
/**
* struct iio_trigger_ops - operations structure for an iio_trigger.
@@ -29,6 +30,7 @@ struct iio_subirq {
* use count is zero (may be NULL)
* @validate_device: function to validate the device when the
* current trigger gets changed.
+ * @validate_trigger: function to validate the parent trigger (may be NULL)
*
* This is typically static const within a driver and shared by
* instances of a given device.
@@ -39,9 +41,10 @@ struct iio_trigger_ops {
int (*try_reenable)(struct iio_trigger *trig);
int (*validate_device)(struct iio_trigger *trig,
struct iio_dev *indio_dev);
+ int (*validate_trigger)(struct iio_trigger *trig,
+ struct iio_trigger *parent);
};
-
/**
* struct iio_trigger - industrial I/O trigger device
* @ops: [DRIVER] operations structure
@@ -59,6 +62,7 @@ struct iio_trigger_ops {
* @attached_own_device:[INTERN] if we are using our own device as trigger,
* i.e. if we registered a poll function to the same
* device as the one providing the trigger.
+ * @parent_trigger: [INTERN] parent trigger
**/
struct iio_trigger {
const struct iio_trigger_ops *ops;
@@ -77,6 +81,7 @@ struct iio_trigger {
unsigned long pool[BITS_TO_LONGS(CONFIG_IIO_CONSUMERS_PER_TRIGGER)];
struct mutex pool_lock;
bool attached_own_device;
+ struct iio_trigger *parent_trigger;
};
--
1.9.1
--
To unsubscribe from this list: send the line "unsubscribe linux-iio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
