xpadneo, rumble: Do not send rumble commands unless ready

We shouldn't allow games to run rumble commands until we are actually
fully initialized. This allows us to announce rumble support early now
which may fix some rare racing with SDL rumble support.

We can now run rumble tests while a concurrent application already
queries rumble or sends rumble commands, and only then enable the
worker and hardware access.

Fixes: #387
Fixes: #444
Signed-off-by: Kai Krakow <kai@kaishome.de>

Author: kakra

hid-xpadneo/src/xpadneo/rumble.c

@@ -9,6 +9,7 @@
 
 #include <linux/delay.h>
 #include <linux/module.h>
+#include <linux/smp.h>
 
 #include "xpadneo.h"
 #include "helpers.h"
@@ -87,6 +88,10 @@ static void rumble_worker(struct work_struct *work)
 		/* let our scheduler know we've been called */
 		xdata->rumble.scheduled = false;
 
+		/* only proceed once initialization data is globally visible */
+		if (unlikely(!smp_load_acquire(&xdata->rumble.enabled)))
+			return;
+
 		if (unlikely(xdata->quirks & XPADNEO_QUIRK_NO_TRIGGER_RUMBLE)) {
 			/* do not send these bits if not supported */
 			r->data.enable &= ~XBOX_RUMBLE_TRIGGERS;
@@ -161,7 +166,11 @@ static int rumble_play(struct input_dev *dev, void *data, struct ff_effect *effe
 	struct hid_device *hdev = input_get_drvdata(dev);
 	struct xpadneo_devdata *xdata = hid_get_drvdata(hdev);
 
-	if (effect->type != FF_RUMBLE)
+	/* do not let FF clients run before rumble state is ready */
+	if (unlikely(!smp_load_acquire(&xdata->rumble.enabled)))
+		return 0;
+
+	if (unlikely(effect->type != FF_RUMBLE))
 		return 0;
 
 	/* copy data from effect structure at the very beginning */
@@ -343,6 +352,10 @@ int xpadneo_rumble_init(struct hid_device *hdev)
 {
 	struct xpadneo_devdata *xdata = hid_get_drvdata(hdev);
 	struct input_dev *gamepad = xdata->gamepad.idev;
+	int ret;
+
+	/* publish that rumble is not ready until init finishes */
+	smp_store_release(&xdata->rumble.enabled, false);
 
 	spin_lock_init(&xdata->rumble.lock);
 	INIT_DELAYED_WORK(&xdata->rumble.worker, rumble_worker);
@@ -355,14 +368,22 @@ int xpadneo_rumble_init(struct hid_device *hdev)
 	if (param_trigger_rumble_mode == PARAM_TRIGGER_RUMBLE_DISABLE)
 		xdata->quirks |= XPADNEO_QUIRK_NO_TRIGGER_RUMBLE;
 
-	if (param_ff_connect_notify)
-		xpadneo_benchmark(rumble_welcome, hdev);
-
 	/* initialize our rumble command throttle */
 	xdata->rumble.throttle_until = RUMBLE_THROTTLE_JIFFIES;
 
+	/* set capabilities */
 	input_set_capability(gamepad, EV_FF, FF_RUMBLE);
-	return input_ff_create_memless(gamepad, NULL, rumble_play);
+	ret = input_ff_create_memless(gamepad, NULL, rumble_play);
+	if (ret)
+		return ret;
+
+	if (param_ff_connect_notify)
+		xpadneo_benchmark(rumble_welcome, hdev);
+
+	/* publish readiness once all rumble state is initialized */
+	smp_store_release(&xdata->rumble.enabled, true);
+
+	return 0;
 }
 
 int xpadneo_rumble_init_workqueue(void)
@@ -385,5 +406,8 @@ void xpadneo_rumble_destroy_workqueue(void)
 
 void xpadneo_rumble_remove(struct xpadneo_devdata *xdata)
 {
+	/* disable rumble before removable to prevent queueing new data */
+	smp_store_release(&xdata->rumble.enabled, false);
+
 	cancel_delayed_work_sync(&xdata->rumble.worker);
 }

hid-xpadneo/src/xpadneo/xpadneo.h

@@ -173,7 +173,7 @@ struct xpadneo_devdata {
 		spinlock_t lock;
 		struct delayed_work worker;
 		unsigned long throttle_until;
-		bool scheduled;
+		bool scheduled, enabled;
 		struct xpadneo_rumble_data data;
 		struct xpadneo_rumble_data shadow;
 		void *output_report_dmabuf;