[PATCH v3] HID: corsair-void: Update power supply values with a unified work handler

[Stuart Hayhurst <stuart.a.hayhurst@gmail.com>]

corsair_void_process_receiver can be called from an interrupt context,
locking battery_mutex in it was causing a kernel panic.
Fix it by moving the critical section into its own work, sharing this
work with battery_add_work and battery_remove_work to remove the need
for any locking

Closes: https://bugzilla.suse.com/show_bug.cgi?id=1236843
Fixes: 6ea2a6fd3872 ("HID: corsair-void: Add Corsair Void headset family driver")
Cc: stable@vger.kernel.org
Signed-off-by: Stuart Hayhurst <stuart.a.hayhurst@gmail.com>
---

v2 -> v3:
 - Use an enum instead of a define for battery flag values
 - Use an integer instead of BIT() for the bit index
 - Drop unhelpful comments
 - Simplify corsair_void_battery_work_handler logic
 - Remove extra newline in commit message
v1 -> v2:
 - Actually remove the mutex

---
 drivers/hid/hid-corsair-void.c | 83 ++++++++++++++++++----------------
 1 file changed, 43 insertions(+), 40 deletions(-)

diff --git a/drivers/hid/hid-corsair-void.c b/drivers/hid/hid-corsair-void.c
index 56e858066c3c..afbd67aa9719 100644
--- a/drivers/hid/hid-corsair-void.c
+++ b/drivers/hid/hid-corsair-void.c
@@ -71,11 +71,9 @@
 
 #include <linux/bitfield.h>
 #include <linux/bitops.h>
-#include <linux/cleanup.h>
 #include <linux/device.h>
 #include <linux/hid.h>
 #include <linux/module.h>
-#include <linux/mutex.h>
 #include <linux/power_supply.h>
 #include <linux/usb.h>
 #include <linux/workqueue.h>
@@ -120,6 +118,12 @@ enum {
 	CORSAIR_VOID_BATTERY_CHARGING	= 5,
 };
 
+enum {
+	CORSAIR_VOID_ADD_BATTERY	= 0,
+	CORSAIR_VOID_REMOVE_BATTERY	= 1,
+	CORSAIR_VOID_UPDATE_BATTERY	= 2,
+};
+
 static enum power_supply_property corsair_void_battery_props[] = {
 	POWER_SUPPLY_PROP_STATUS,
 	POWER_SUPPLY_PROP_PRESENT,
@@ -155,12 +159,12 @@ struct corsair_void_drvdata {
 
 	struct power_supply *battery;
 	struct power_supply_desc battery_desc;
-	struct mutex battery_mutex;
 
 	struct delayed_work delayed_status_work;
 	struct delayed_work delayed_firmware_work;
-	struct work_struct battery_remove_work;
-	struct work_struct battery_add_work;
+
+	unsigned long battery_work_flags;
+	struct work_struct battery_work;
 };
 
 /*
@@ -260,11 +264,9 @@ static void corsair_void_process_receiver(struct corsair_void_drvdata *drvdata,
 
 	/* Inform power supply if battery values changed */
 	if (memcmp(&orig_battery_data, battery_data, sizeof(*battery_data))) {
-		scoped_guard(mutex, &drvdata->battery_mutex) {
-			if (drvdata->battery) {
-				power_supply_changed(drvdata->battery);
-			}
-		}
+		set_bit(CORSAIR_VOID_UPDATE_BATTERY,
+			&drvdata->battery_work_flags);
+		schedule_work(&drvdata->battery_work);
 	}
 }
 
@@ -536,29 +538,11 @@ static void corsair_void_firmware_work_handler(struct work_struct *work)
 
 }
 
-static void corsair_void_battery_remove_work_handler(struct work_struct *work)
-{
-	struct corsair_void_drvdata *drvdata;
-
-	drvdata = container_of(work, struct corsair_void_drvdata,
-			       battery_remove_work);
-	scoped_guard(mutex, &drvdata->battery_mutex) {
-		if (drvdata->battery) {
-			power_supply_unregister(drvdata->battery);
-			drvdata->battery = NULL;
-		}
-	}
-}
-
-static void corsair_void_battery_add_work_handler(struct work_struct *work)
+static void corsair_void_add_battery(struct corsair_void_drvdata *drvdata)
 {
-	struct corsair_void_drvdata *drvdata;
 	struct power_supply_config psy_cfg = {};
 	struct power_supply *new_supply;
 
-	drvdata = container_of(work, struct corsair_void_drvdata,
-			       battery_add_work);
-	guard(mutex)(&drvdata->battery_mutex);
 	if (drvdata->battery)
 		return;
 
@@ -583,16 +567,42 @@ static void corsair_void_battery_add_work_handler(struct work_struct *work)
 	drvdata->battery = new_supply;
 }
 
+static void corsair_void_battery_work_handler(struct work_struct *work)
+{
+	struct corsair_void_drvdata *drvdata = container_of(work,
+		struct corsair_void_drvdata, battery_work);
+
+	bool add_battery = test_and_clear_bit(CORSAIR_VOID_ADD_BATTERY,
+					      &drvdata->battery_work_flags);
+	bool remove_battery = test_and_clear_bit(CORSAIR_VOID_REMOVE_BATTERY,
+						 &drvdata->battery_work_flags);
+	bool update_battery = test_and_clear_bit(CORSAIR_VOID_UPDATE_BATTERY,
+						 &drvdata->battery_work_flags);
+
+	if (add_battery && !remove_battery) {
+		corsair_void_add_battery(drvdata);
+	} else if (remove_battery && !add_battery && drvdata->battery) {
+		power_supply_unregister(drvdata->battery);
+		drvdata->battery = NULL;
+	}
+
+	if (update_battery && drvdata->battery)
+		power_supply_changed(drvdata->battery);
+
+}
+
 static void corsair_void_headset_connected(struct corsair_void_drvdata *drvdata)
 {
-	schedule_work(&drvdata->battery_add_work);
+	set_bit(CORSAIR_VOID_ADD_BATTERY, &drvdata->battery_work_flags);
+	schedule_work(&drvdata->battery_work);
 	schedule_delayed_work(&drvdata->delayed_firmware_work,
 			      msecs_to_jiffies(100));
 }
 
 static void corsair_void_headset_disconnected(struct corsair_void_drvdata *drvdata)
 {
-	schedule_work(&drvdata->battery_remove_work);
+	set_bit(CORSAIR_VOID_REMOVE_BATTERY, &drvdata->battery_work_flags);
+	schedule_work(&drvdata->battery_work);
 
 	corsair_void_set_unknown_wireless_data(drvdata);
 	corsair_void_set_unknown_batt(drvdata);
@@ -678,13 +688,7 @@ static int corsair_void_probe(struct hid_device *hid_dev,
 	drvdata->battery_desc.get_property = corsair_void_battery_get_property;
 
 	drvdata->battery = NULL;
-	INIT_WORK(&drvdata->battery_remove_work,
-		  corsair_void_battery_remove_work_handler);
-	INIT_WORK(&drvdata->battery_add_work,
-		  corsair_void_battery_add_work_handler);
-	ret = devm_mutex_init(drvdata->dev, &drvdata->battery_mutex);
-	if (ret)
-		return ret;
+	INIT_WORK(&drvdata->battery_work, corsair_void_battery_work_handler);
 
 	ret = sysfs_create_group(&hid_dev->dev.kobj, &corsair_void_attr_group);
 	if (ret)
@@ -721,8 +725,7 @@ static void corsair_void_remove(struct hid_device *hid_dev)
 	struct corsair_void_drvdata *drvdata = hid_get_drvdata(hid_dev);
 
 	hid_hw_stop(hid_dev);
-	cancel_work_sync(&drvdata->battery_remove_work);
-	cancel_work_sync(&drvdata->battery_add_work);
+	cancel_work_sync(&drvdata->battery_work);
 	if (drvdata->battery)
 		power_supply_unregister(drvdata->battery);
 
-- 
2.47.2