[PATCH v7 03/16] power: sequencing: Add pwrseq_get_state()

The power sequencing consumer API already does power on state tracking
internally. Expose the state to consumers through pwrseq_get_state()
so that they don't have to reimplement it locally.

Instead of just on/off and error codes, the function can also return
"unknown" state. This is in anticipation for "uncontrollable" power
sequencers (such as GPIOs left unconnected).

Acked-by: Bartosz Golaszewski <[email protected]>
Signed-off-by: Chen-Yu Tsai <[email protected]>
---
Changes since v6:
- Changed to pwrseq_get_state() with enum return value

Changes since v5:
- Reverted back to returning -EINVAL if descriptor is NULL

Changes since v4:
- Make pwrseq_power_is_on() return 1 if descriptor is NULL, i.e. if
  the descriptor is optional, matching the other pwrseq consumer APIs

Changes since v3:
- Added missing stub function for !POWER_SEQUENCING

Changes since v2:
- New patch

Needs to go in with "usb: hub: Power on connected M.2 E-key connectors"
as it is a build time dependency. Bartosz wants the change on an
immutable branch to pull into the pwrseq tree.
---
 drivers/power/sequencing/core.c | 19 +++++++++++++++++++
 include/linux/pwrseq/consumer.h | 12 ++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/drivers/power/sequencing/core.c b/drivers/power/sequencing/core.c
index 02f42da91598..701728e60a26 100644
--- a/drivers/power/sequencing/core.c
+++ b/drivers/power/sequencing/core.c
@@ -968,6 +968,25 @@ int pwrseq_power_off(struct pwrseq_desc *desc)
 }
 EXPORT_SYMBOL_GPL(pwrseq_power_off);
 
+/**
+ * pwrseq_get_state() - Queries the last requested state of the power sequencer.
+ * @desc: Descriptor referencing the power sequencer.
+ *
+ * This returns the last requested state of the power sequencer.
+ *
+ * Returns:
+ * On success, PWRSEQ_STATE_ON for on and PWRSEQ_STATE_OFF for off;
+ * negative error number on failure.
+ */
+int pwrseq_get_state(struct pwrseq_desc *desc)
+{
+	if (!desc)
+		return -EINVAL;
+
+	return desc->powered_on ? PWRSEQ_STATE_ON : PWRSEQ_STATE_OFF;
+}
+EXPORT_SYMBOL_GPL(pwrseq_get_state);
+
 /**
  * pwrseq_to_device() - Get the pwrseq device pointer from a descriptor.
  * @desc: Descriptor referencing the power sequencer.
diff --git a/include/linux/pwrseq/consumer.h b/include/linux/pwrseq/consumer.h
index 3c907c9e1885..af949e756bbd 100644
--- a/include/linux/pwrseq/consumer.h
+++ b/include/linux/pwrseq/consumer.h
@@ -11,6 +11,12 @@
 struct device;
 struct pwrseq_desc;
 
+enum {
+	PWRSEQ_STATE_UNKNOWN,
+	PWRSEQ_STATE_ON,
+	PWRSEQ_STATE_OFF,
+};
+
 #if IS_ENABLED(CONFIG_POWER_SEQUENCING)
 
 struct pwrseq_desc * __must_check
@@ -22,6 +28,7 @@ devm_pwrseq_get(struct device *dev, const char *target);
 
 int pwrseq_power_on(struct pwrseq_desc *desc);
 int pwrseq_power_off(struct pwrseq_desc *desc);
+int pwrseq_get_state(struct pwrseq_desc *desc);
 
 struct device *pwrseq_to_device(struct pwrseq_desc *desc);
 
@@ -53,6 +60,11 @@ static inline int pwrseq_power_off(struct pwrseq_desc *desc)
 	return -ENOSYS;
 }
 
+static inline int pwrseq_get_state(struct pwrseq_desc *desc)
+{
+	return -ENOSYS;
+}
+
 static inline struct device *pwrseq_to_device(struct pwrseq_desc *desc)
 {
 	return NULL;
-- 
2.55.0.229.g6434b31f56-goog