HID: wacom: remove the battery when the EKR is off

Currently the EKR battery remains even after we stop getting information
from the device. This can lead to a stale battery persisting indefinitely
in userspace.

The remote sends a heartbeat every 10 seconds. Delete the battery if we
miss two heartbeats (after 21 seconds). Restore the battery once we see
a heartbeat again.

Signed-off-by: Aaron Skomra <skomra@gmail.com>
Signed-off-by: Aaron Armstrong Skomra <aaron.skomra@wacom.com>
Reviewed-by: Jason Gerecke <jason.gerecke@wacom.com>
Fixes: 9f1015d ("HID: wacom: EKR: attach the power_supply on first connection")
CC: stable@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom.h

@@ -150,6 +150,7 @@ struct wacom_remote {
 		struct input_dev *input;
 		bool registered;
 		struct wacom_battery battery;
+		ktime_t active_time;
 	} remotes[WACOM_MAX_REMOTES];
 };
 

drivers/hid/wacom_sys.c

@@ -2523,6 +2523,18 @@ static void wacom_wireless_work(struct work_struct *work)
 	return;
 }
 
+static void wacom_remote_destroy_battery(struct wacom *wacom, int index)
+{
+	struct wacom_remote *remote = wacom->remote;
+
+	if (remote->remotes[index].battery.battery) {
+		devres_release_group(&wacom->hdev->dev,
+				     &remote->remotes[index].battery.bat_desc);
+		remote->remotes[index].battery.battery = NULL;
+		remote->remotes[index].active_time = 0;
+	}
+}
+
 static void wacom_remote_destroy_one(struct wacom *wacom, unsigned int index)
 {
 	struct wacom_remote *remote = wacom->remote;
@@ -2537,17 +2549,14 @@ static void wacom_remote_destroy_one(struct wacom *wacom, unsigned int index)
 			remote->remotes[i].registered = false;
 			spin_unlock_irqrestore(&remote->remote_lock, flags);
 
-			if (remote->remotes[i].battery.battery)
-				devres_release_group(&wacom->hdev->dev,
-						     &remote->remotes[i].battery.bat_desc);
+			wacom_remote_destroy_battery(wacom, i);
 
 			if (remote->remotes[i].group.name)
 				devres_release_group(&wacom->hdev->dev,
 						     &remote->remotes[i]);
 
 			remote->remotes[i].serial = 0;
 			remote->remotes[i].group.name = NULL;
-			remote->remotes[i].battery.battery = NULL;
 			wacom->led.groups[i].select = WACOM_STATUS_UNKNOWN;
 		}
 	}
@@ -2632,6 +2641,9 @@ static int wacom_remote_attach_battery(struct wacom *wacom, int index)
 	if (remote->remotes[index].battery.battery)
 		return 0;
 
+	if (!remote->remotes[index].active_time)
+		return 0;
+
 	if (wacom->led.groups[index].select == WACOM_STATUS_UNKNOWN)
 		return 0;
 
@@ -2647,6 +2659,7 @@ static void wacom_remote_work(struct work_struct *work)
 {
 	struct wacom *wacom = container_of(work, struct wacom, remote_work);
 	struct wacom_remote *remote = wacom->remote;
+	ktime_t kt = ktime_get();
 	struct wacom_remote_data data;
 	unsigned long flags;
 	unsigned int count;
@@ -2673,6 +2686,10 @@ static void wacom_remote_work(struct work_struct *work)
 		serial = data.remote[i].serial;
 		if (data.remote[i].connected) {
 
+			if (kt - remote->remotes[i].active_time > WACOM_REMOTE_BATTERY_TIMEOUT
+			    && remote->remotes[i].active_time != 0)
+				wacom_remote_destroy_battery(wacom, i);
+
 			if (remote->remotes[i].serial == serial) {
 				wacom_remote_attach_battery(wacom, i);
 				continue;

drivers/hid/wacom_wac.c

@@ -1134,6 +1134,7 @@ static int wacom_remote_irq(struct wacom_wac *wacom_wac, size_t len)
 	if (index < 0 || !remote->remotes[index].registered)
 		goto out;
 
+	remote->remotes[i].active_time = ktime_get();
 	input = remote->remotes[index].input;
 
 	input_report_key(input, BTN_0, (data[9] & 0x01));

drivers/hid/wacom_wac.h

@@ -13,6 +13,7 @@
 #define WACOM_NAME_MAX		64
 #define WACOM_MAX_REMOTES	5
 #define WACOM_STATUS_UNKNOWN	255
+#define WACOM_REMOTE_BATTERY_TIMEOUT	21000000000ll
 
 /* packet length for individual models */
 #define WACOM_PKGLEN_BBFUN	 9