[PATCH] HID: hid-msi: Drain orphan MCU ACKs by issuing a query

[Kenhou Iijima <kenhou@kenhou.net>]

The Claw MCU re-sends an unhandled ACK roughly every 2 seconds until it
receives another command. When an ACK arrives with waiting_cmd set to
CLAW_COMMAND_TYPE_NONE, such as after a command is written through
hidraw or once orphan_ack_pending has been cleared without a subsequent
command, the driver currently logs "Got unexpected ACK from MCU,
ignoring" on every re-transmission and never clears the MCU's pending
ACK state.

Schedule a work item that issues a harmless READ_GAMEPAD_MODE query when
an unexpected ACK arrives. Receiving any command causes the MCU to stop
re-sending the pending ACK, eliminating the repeated events and log
spam.

Fixes: a9517958e828 ("HID: hid-msi: Add MSI Claw configuration driver")
Signed-off-by: Kenhou Iijima <kenhou@kenhou.net>
---
Tested on an MSI Claw 8 AI+ A2VM (0db0:1901, bcdDevice 2.30).

 drivers/hid/hid-msi.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-msi.c b/drivers/hid/hid-msi.c
index 23d731f700..e52923fcc8 100644
--- a/drivers/hid/hid-msi.c
+++ b/drivers/hid/hid-msi.c
@@ -332,6 +332,7 @@ struct claw_drvdata {
 	enum claw_profile_ack_pending profile_pending;
 	struct completion orphan_ack_complete;
 	struct completion send_cmd_complete;
+	struct work_struct orphan_ack_work;
 	struct delayed_work cfg_resume;
 	struct delayed_work cfg_setup;
 	spinlock_t registration_lock; /* Lock for registration read/write */
@@ -532,7 +533,12 @@ static int claw_raw_event(struct claw_drvdata *drvdata, struct hid_report *repor
 		}
 
 		if (drvdata->waiting_cmd == CLAW_COMMAND_TYPE_NONE) {
-			dev_warn(&drvdata->hdev->dev, "Got unexpected ACK from MCU, ignoring\n");
+			/*
+			 * The MCU re-sends an unhandled ACK roughly every 2 s
+			 * until it receives another command. Drain it by
+			 * scheduling a harmless query so the ACK storm stops.
+			 */
+			schedule_work(&drvdata->orphan_ack_work);
 			break;
 		}
 
@@ -653,6 +659,20 @@ static int claw_hw_output_report(struct hid_device *hdev, u8 index, u8 *data,
 	return __claw_hw_output_report(hdev, index, data, len, timeout);
 }
 
+static void claw_orphan_ack_drain(struct work_struct *work)
+{
+	struct claw_drvdata *drvdata = container_of(work, struct claw_drvdata,
+						    orphan_ack_work);
+
+	/*
+	 * A query is enough to make the MCU stop re-sending the pending ACK.
+	 * claw_hw_output_report() also waits for any orphan ACK before
+	 * sending, so this cannot interleave with a real command sequence.
+	 */
+	claw_hw_output_report(drvdata->hdev, CLAW_COMMAND_TYPE_READ_GAMEPAD_MODE,
+			      NULL, 0, 25);
+}
+
 static int claw_switch_mode(struct hid_device *hdev, enum claw_mode_field field, u8 val)
 {
 	struct claw_drvdata *drvdata = hid_get_drvdata(hdev);
@@ -1868,6 +1888,7 @@ static int claw_probe(struct hid_device *hdev, u8 ep)
 	spin_lock_init(&drvdata->rumble_lock);
 	init_completion(&drvdata->orphan_ack_complete);
 	init_completion(&drvdata->send_cmd_complete);
+	INIT_WORK(&drvdata->orphan_ack_work, &claw_orphan_ack_drain);
 	INIT_DELAYED_WORK(&drvdata->cfg_resume, &cfg_resume_fn);
 	INIT_DELAYED_WORK(&drvdata->cfg_setup, &cfg_setup_fn);
 	INIT_DELAYED_WORK(&drvdata->rgb_queue, &claw_rgb_queue_fn);
@@ -1934,6 +1955,7 @@ static void claw_remove(struct hid_device *hdev)
 
 	cancel_delayed_work_sync(&drvdata->cfg_resume);
 	cancel_delayed_work_sync(&drvdata->cfg_setup);
+	cancel_work_sync(&drvdata->orphan_ack_work);
 
 	scoped_guard(spinlock_irqsave, &drvdata->registration_lock) {
 		/* Pairs with smp_store_release from cfg_setup_fn in system_wq context */
@@ -2014,6 +2036,7 @@ static int claw_suspend(struct hid_device *hdev)
 
 	cancel_delayed_work_sync(&drvdata->cfg_resume);
 	cancel_delayed_work_sync(&drvdata->cfg_setup);
+	cancel_work_sync(&drvdata->orphan_ack_work);
 	cancel_delayed_work_sync(&drvdata->rgb_queue);
 
 	return 0;
-- 
2.56.0