[PATCH] platform/x86: asus-wmi: do not enforce a battery charge threshold

[Denis Benato]

Users are complaining for the battery limit being reset at 100% during
the boot process while the general consensus appears to not apply
unsolecited hardware changes, therefore stop resetting the battery
charge limit at boot and return -ENODATA on charge_end_threshold to
signal for an unknown limit.

Suggested-by: Antheas Kapenekakis <lkml@xxxxxxxxxxx>
Suggested-by: Derek J. Clark <derekjohn.clark@xxxxxxxxx>
Signed-off-by: Denis Benato <denis.benato@xxxxxxxxx>
---
 drivers/platform/x86/asus-wmi.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 6ba49bd375df..dc330a8ee2f2 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1557,7 +1557,10 @@ static ssize_t charge_control_end_threshold_show(struct device *device,
 						 struct device_attribute *attr,
 						 char *buf)
 {
-	return sysfs_emit(buf, "%d\n", charge_end_threshold);
+	if ((charge_end_threshold >= 0) && (charge_end_threshold <= 100))
+		return sysfs_emit(buf, "%d\n", charge_end_threshold);
+
+	return -ENODATA;
 }
 
 static DEVICE_ATTR_RW(charge_control_end_threshold);
@@ -1580,11 +1583,11 @@ static int asus_wmi_battery_add(struct power_supply *battery, struct acpi_batter
 		return -ENODEV;
 
 	/* The charge threshold is only reset when the system is power cycled,
-	 * and we can't get the current threshold so let set it to 100% when
-	 * a battery is added.
+	 * and we can't read the current threshold, however the majority of
+	 * platforms retains it, therefore signal the threshold as unknown
+	 * until user explicitly sets it to a new value.
 	 */
-	asus_wmi_set_devstate(ASUS_WMI_DEVID_RSOC, 100, NULL);
-	charge_end_threshold = 100;
+	charge_end_threshold = -1;
 
 	return 0;
 }
-- 
2.53.0