[PATCH v7 3/4] power: supply: core: add wireless signal strength property

[Qiwu Huang <yanziily@gmail.com>]

From: Qiwu Huang <huangqiwu@xiaomi.com>

reports wireless signal strength.
The value show degree of coupling between tx and rx.

Signed-off-by: Qiwu Huang <huangqiwu@xiaomi.com>
---
 Documentation/ABI/testing/sysfs-class-power | 22 +++++++++++++++++++++
 drivers/power/supply/power_supply_sysfs.c   |  1 +
 include/linux/power_supply.h                |  1 +
 3 files changed, 24 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-power b/Documentation/ABI/testing/sysfs-class-power
index 03ab449fae8a..4459b720feb2 100644
--- a/Documentation/ABI/testing/sysfs-class-power
+++ b/Documentation/ABI/testing/sysfs-class-power
@@ -757,3 +757,25 @@ Description:
 			13: ADAPTER_VOICE_BOX,
 			14: ADAPTER_PRIVATE_PD_50W.
 
+What:		/sys/class/power_supply/<supply_name>/signal_strength
+Date:		Jul 2020
+Contact:	Fei Jiang <jiangfei1@xiaomi.com>
+Description:
+		In PING phase, RX transmits a signal strength packet as the
+		first communication packet to instruct the base to keep power
+		signal on.The value reports wireless signal strength and show
+		degree of coupling.
+
+		The Qi Wireless Power Transfer System is published by the
+		Wireless Power Consortium.The ping phase is the necessary stage
+		for matching transmitter and receiver. In this phase,the Power
+		Transmitter executes a Digital Ping, and listens for a response.
+		If the Power Transmitter discovers a Power Receiver, the Power
+		Transmitter may extend the Digital Ping,i.e. maintain the Power
+		Signal at the level of the Digital Ping. This causes the system
+		to proceed to the identification & configuration phase. If the
+		Power Transmitter does not extend the Digital Ping, the system
+		shall revert to the selection phase.
+
+		Access: Read-Only
+		Valid values: 0 - 100
diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
index f2458e21d02b..e420a453095e 100644
--- a/drivers/power/supply/power_supply_sysfs.c
+++ b/drivers/power/supply/power_supply_sysfs.c
@@ -208,6 +208,7 @@ static struct power_supply_attr power_supply_attrs[] = {
 	POWER_SUPPLY_ATTR(SERIAL_NUMBER),
 	POWER_SUPPLY_ATTR(QUICK_CHARGE_TYPE),
 	POWER_SUPPLY_ATTR(TX_ADAPTER),
+	POWER_SUPPLY_ATTR(SIGNAL_STRENGTH),
 };
 
 static struct attribute *
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index 0bbdec1630a4..346c6c9c0737 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -169,6 +169,7 @@ enum power_supply_property {
 	POWER_SUPPLY_PROP_SERIAL_NUMBER,
 	POWER_SUPPLY_PROP_QUICK_CHARGE_TYPE,
 	POWER_SUPPLY_PROP_TX_ADAPTER,
+	POWER_SUPPLY_PROP_SIGNAL_STRENGTH,
 };
 
 enum power_supply_type {
-- 
2.27.0