From 37d1601938349e79e9c31a8aba431d5543e09e72 Mon Sep 17 00:00:00 2001
From: Jason Gerecke <killertofu@gmail.com>
Date: Fri, 28 Apr 2017 09:25:30 -0700
Subject: [PATCH] HID: wacom: generic: Scale battery capacity measurements to percentages
Git-commit: 37d1601938349e79e9c31a8aba431d5543e09e72
Patch-mainline: v4.13-rc1
References: bsc#1051510

The power_supply subsystem expects us to provide it with capacity values
measured in percent. In particular, AES devices (HID_DG_BATTERYSTRENGTH)
use the range 0-255, which needs to be rescaled. The MobileStudio Pro
(WACOM_HID_WD_BATTERY_LEVEL) uses the range 0-100, but there's no guarantee
that future devices will share the same range.

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Ping Cheng <ping.cheng@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/hid/wacom_wac.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 4b225fb19a16..fd989e09ae2d 100644
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -1811,6 +1811,7 @@ static void wacom_wac_pad_battery_event(struct hid_device *hdev, struct hid_fiel
 
 	switch (equivalent_usage) {
 	case WACOM_HID_WD_BATTERY_LEVEL:
+		value = value * 100 / (field->logical_maximum - field->logical_minimum);
 		wacom_wac->hid_data.battery_capacity = value;
 		wacom_wac->hid_data.bat_connected = 1;
 		break;
@@ -2035,6 +2036,7 @@ static void wacom_wac_pen_event(struct hid_device *hdev, struct hid_field *field
 			wacom_wac->hid_data.sense_state = value;
 		return;
 	case HID_DG_BATTERYSTRENGTH:
+		value = value * 100 / (field->logical_maximum - field->logical_minimum);
 		wacom_wac->hid_data.battery_capacity = value;
 		wacom_wac->hid_data.bat_connected = 1;
 		break;
-- 
2.16.4