[RFC PATCH 1/2] iio: core: implement iio_{claim|release}_direct_mode()

Alison Schofield
2016-03-01T19:02:59Z

It is often the case that the driver wants to be sure a device stays
in direct mode while it is executing a task or series of tasks. To
accomplish this today, the driver performs this sequence: 1) take the
device state lock, 2)verify it is not in a buffered mode, 3) execute
some tasks, and 4) release that lock.

This patch introduces a pair of helper functions that simplify these
steps and make it more semantically expressive.

iio_claim_direct_mode()
If the device is not in any buffered mode it is guaranteed
to stay that way until iio_release_direct_mode() is called.

iio_release_direct_mode()
Release the claim. Device is no longer guaranteed to stay
in direct mode.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
---
drivers/iio/industrialio-core.c | 39 +++++++++++++++++++++++++++++++++++++++
include/linux/iio/iio.h | 2 ++
2 files changed, 41 insertions(+)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 70cb7eb..f6f0c89 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -25,6 +25,7 @@
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/debugfs.h>
+#include <linux/mutex.h>
#include <linux/iio/iio.h>
#include "iio_core.h"
#include "iio_core_trigger.h"
@@ -1375,6 +1376,44 @@ void devm_iio_device_unregister(struct device *dev, struct iio_dev *indio_dev)
}
EXPORT_SYMBOL_GPL(devm_iio_device_unregister);

+/**
+ * iio_claim_direct_mode - Keep device in direct mode
+ * @indio_dev: the iio_dev associated with the device
+ *
+ * If the device is in direct mode it is guaranteed to
+ * stay that way until iio_release_direct_mode() is called.
+ *
+ * Use with iio_release_direct_mode()
+ *
+ * Returns: 0 on success, -EINVAL on failure
+ */
+int iio_claim_direct_mode(struct iio_dev *indio_dev)
+{
+ mutex_lock(&indio_dev->mlock);
+
+ if (iio_buffer_enabled(indio_dev)) {
+ mutex_unlock(&indio_dev->mlock);
+ return -EINVAL;
+ }
+ return 0;
+}
+EXPORT_SYMBOL_GPL(iio_claim_direct_mode);
+
+/**
+ * iio_release_direct_mode - releases claim on direct mode
+ * @indio_dev: the iio_dev associated with the device
+ *
+ * Release the claim. Device is no longer guaranteed to stay
+ * in direct mode.
+ *
+ * Use with iio_claim_direct_mode()
+ */
+void iio_release_direct_mode(struct iio_dev *indio_dev)
+{
+ mutex_unlock(&indio_dev->mlock);
+}
+EXPORT_SYMBOL_GPL(iio_release_direct_mode);
+
subsys_initcall(iio_init);
module_exit(iio_exit);

diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index ce9e9c1..9efe2af 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -527,6 +527,8 @@ void iio_device_unregister(struct iio_dev *indio_dev);
int devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev);
void devm_iio_device_unregister(struct device *dev, struct iio_dev *indio_dev);
int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp);
+int iio_claim_direct_mode(struct iio_dev *indio_dev);
+void iio_release_direct_mode(struct iio_dev *indio_dev);

extern struct bus_type iio_bus_type;

--
2.1.4