[PATCH 09/21] HID: stadia: use open/close to manage workqueue lifecycle

[Dmitry Torokhov]

Override input device open() and close() callbacks to enable and disable
the force-feedback workqueue item synchronously.

When the input device is opened by userspace, call hid_hw_open() and
enable_work(). When it is closed, disable_work_sync() ensures that any
pending or running work item is cancelled/flushed and no further work
items can be scheduled.

In close(), zero out magnitudes and issue a final report to turn off the
rumble motors on the physical controller before shutting down transport
I/O.

Pack strong and weak magnitudes into a single u32 integer using
WRITE_ONCE() and READ_ONCE() for atomic, lockless updates.

This allows eliminating the manual 'removed' boolean flag and spinlock
completely.

Assisted-by: Antigravity:gemini-3.6-flash
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
---
 drivers/hid/hid-google-stadiaff.c | 71 +++++++++++++++++++++------------------
 1 file changed, 38 insertions(+), 33 deletions(-)

diff --git a/drivers/hid/hid-google-stadiaff.c b/drivers/hid/hid-google-stadiaff.c
index 6b38d2421d3d..d6a73d210599 100644
--- a/drivers/hid/hid-google-stadiaff.c
+++ b/drivers/hid/hid-google-stadiaff.c
@@ -17,10 +17,7 @@
 struct stadiaff_device {
 	struct hid_device *hid;
 	struct hid_report *report;
-	spinlock_t lock;
-	bool removed;
-	uint16_t strong_magnitude;
-	uint16_t weak_magnitude;
+	u32 magnitudes;
 	struct work_struct work;
 };
 
@@ -29,12 +26,10 @@ static void stadiaff_work(struct work_struct *work)
 	struct stadiaff_device *stadiaff =
 		container_of(work, struct stadiaff_device, work);
 	struct hid_field *rumble_field = stadiaff->report->field[0];
-	unsigned long flags;
+	u32 mags = READ_ONCE(stadiaff->magnitudes);
 
-	spin_lock_irqsave(&stadiaff->lock, flags);
-	rumble_field->value[0] = stadiaff->strong_magnitude;
-	rumble_field->value[1] = stadiaff->weak_magnitude;
-	spin_unlock_irqrestore(&stadiaff->lock, flags);
+	rumble_field->value[0] = mags & 0xffff;
+	rumble_field->value[1] = (mags >> 16) & 0xffff;
 
 	hid_hw_request(stadiaff->hid, stadiaff->report, HID_REQ_SET_REPORT);
 }
@@ -44,19 +39,41 @@ static int stadiaff_play(struct input_dev *dev, void *data,
 {
 	struct hid_device *hid = input_get_drvdata(dev);
 	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
-	unsigned long flags;
+	u32 mags = (u32)effect->u.rumble.strong_magnitude |
+		  ((u32)effect->u.rumble.weak_magnitude << 16);
 
-	spin_lock_irqsave(&stadiaff->lock, flags);
-	if (!stadiaff->removed) {
-		stadiaff->strong_magnitude = effect->u.rumble.strong_magnitude;
-		stadiaff->weak_magnitude = effect->u.rumble.weak_magnitude;
-		schedule_work(&stadiaff->work);
-	}
-	spin_unlock_irqrestore(&stadiaff->lock, flags);
+	WRITE_ONCE(stadiaff->magnitudes, mags);
+	schedule_work(&stadiaff->work);
 
 	return 0;
 }
 
+static int stadia_input_open(struct input_dev *dev)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+	int error;
+
+	error = hid_hw_open(hid);
+	if (error)
+		return error;
+
+	enable_work(&stadiaff->work);
+	return 0;
+}
+
+static void stadia_input_close(struct input_dev *dev)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+
+	WRITE_ONCE(stadiaff->magnitudes, 0);
+	stadiaff_work(&stadiaff->work);
+	disable_work_sync(&stadiaff->work);
+
+	hid_hw_close(hid);
+}
+
 static int stadiaff_init(struct hid_device *hid)
 {
 	struct stadiaff_device *stadiaff;
@@ -90,11 +107,13 @@ static int stadiaff_init(struct hid_device *hid)
 	if (error)
 		return error;
 
-	stadiaff->removed = false;
 	stadiaff->hid = hid;
 	stadiaff->report = report;
 	INIT_WORK(&stadiaff->work, stadiaff_work);
-	spin_lock_init(&stadiaff->lock);
+	disable_work_sync(&stadiaff->work);
+
+	dev->open = stadia_input_open;
+	dev->close = stadia_input_close;
 
 	hid_info(hid, "Force Feedback for Google Stadia controller\n");
 
@@ -127,19 +146,6 @@ static int stadia_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	return 0;
 }
 
-static void stadia_remove(struct hid_device *hid)
-{
-	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
-	unsigned long flags;
-
-	spin_lock_irqsave(&stadiaff->lock, flags);
-	stadiaff->removed = true;
-	spin_unlock_irqrestore(&stadiaff->lock, flags);
-
-	cancel_work_sync(&stadiaff->work);
-	hid_hw_stop(hid);
-}
-
 static const struct hid_device_id stadia_devices[] = {
 	{ HID_USB_DEVICE(USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STADIA) },
 	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STADIA) },
@@ -151,7 +157,6 @@ static struct hid_driver stadia_driver = {
 	.name = "stadia",
 	.id_table = stadia_devices,
 	.probe = stadia_probe,
-	.remove = stadia_remove,
 };
 module_hid_driver(stadia_driver);
 

-- 
2.55.0.629.g250fe7f194-goog