[PATCHv3] reset: add reset_control_status helper function

[<dinguyen@opensource.altera.com>]

From: Dinh Nguyen <dinguyen@opensource.altera.com>

There are cases where a system will want to read a reset status bit before
doing any other toggling. Add a reset_control_status helper function to the
reset controller API.

Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
---
v3: Remove last unsigned int and update comment
v2: reset_control_status should be returning an int, and add a comment about
    status in reset-controller.h
---
 drivers/reset/core.c             | 15 +++++++++++++++
 include/linux/reset-controller.h |  2 ++
 include/linux/reset.h            |  7 +++++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index baeaf82..7955e00 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -126,6 +126,21 @@ int reset_control_deassert(struct reset_control *rstc)
 EXPORT_SYMBOL_GPL(reset_control_deassert);
 
 /**
+ * reset_control_status - returns a negative errno if not supported, a
+ * positive value if the reset line is asserted, or zero if the reset
+ * line is not asserted.
+ * @rstc: reset controller
+ */
+int reset_control_status(struct reset_control *rstc)
+{
+	if (rstc->rcdev->ops->status)
+		return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);
+
+	return -ENOSYS;
+}
+EXPORT_SYMBOL_GPL(reset_control_status);
+
+/**
  * of_reset_control_get - Lookup and obtain a reference to a reset controller.
  * @node: device to be reset by the controller
  * @id: reset line name
diff --git a/include/linux/reset-controller.h b/include/linux/reset-controller.h
index 41a4695..ce6b962 100644
--- a/include/linux/reset-controller.h
+++ b/include/linux/reset-controller.h
@@ -12,11 +12,13 @@ struct reset_controller_dev;
  *         things to reset the device
  * @assert: manually assert the reset line, if supported
  * @deassert: manually deassert the reset line, if supported
+ * @status: return the status of the reset line, if supported
  */
 struct reset_control_ops {
 	int (*reset)(struct reset_controller_dev *rcdev, unsigned long id);
 	int (*assert)(struct reset_controller_dev *rcdev, unsigned long id);
 	int (*deassert)(struct reset_controller_dev *rcdev, unsigned long id);
+	int (*status)(struct reset_controller_dev *rcdev, unsigned long id);
 };
 
 struct module;
diff --git a/include/linux/reset.h b/include/linux/reset.h
index 349f150..da5602b 100644
--- a/include/linux/reset.h
+++ b/include/linux/reset.h
@@ -10,6 +10,7 @@ struct reset_control;
 int reset_control_reset(struct reset_control *rstc);
 int reset_control_assert(struct reset_control *rstc);
 int reset_control_deassert(struct reset_control *rstc);
+int reset_control_status(struct reset_control *rstc);
 
 struct reset_control *reset_control_get(struct device *dev, const char *id);
 void reset_control_put(struct reset_control *rstc);
@@ -57,6 +58,12 @@ static inline int reset_control_deassert(struct reset_control *rstc)
 	return 0;
 }
 
+static inline int reset_control_status(struct reset_control *rstc)
+{
+	WARN_ON(1);
+	return 0;
+}
+
 static inline void reset_control_put(struct reset_control *rstc)
 {
 	WARN_ON(1);
-- 
2.0.3