[PATCH 6.6.y] HID: magicmouse: re-enable multitouch after reset-resume

[Sasha Levin <sashal@kernel.org>]

From: Christopher Kodama <ckhordiasma@gmail.com>

[ Upstream commit 4253fe22b137c4ee68f36b707fdb1b44b191edc4 ]

When the Apple Magic Trackpad 2 (USB) is reset across a power transition
(e.g. resume from hibernation) it drops out of multitouch mode: it keeps
sending report ID 0x02 on its HID_TYPE_USBMOUSE interface, but the packet
shrinks from 21 to 8 bytes and the trackpad2 handler drops it (size < 12).
Clicks still work but pointer motion is lost until the device is re-plugged
or the driver reloaded.

Re-enable multitouch from .reset_resume via the workqueue.  Only
.reset_resume is needed; suspend-to-idle keeps the device powered and
retains multitouch.

Fixes: 87a2f10395c8 ("HID: magicmouse: Apple Magic Trackpad 2 USB-C driver support")
Cc: stable@vger.kernel.org
Assisted-by: Claude-Code:claude-opus-4-8
Signed-off-by: Christopher Kodama <ckhordiasma@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
[ kept 6.6's non-const `magicmouse_report_fixup()` signature in context instead of upstream's `static const __u8 *` ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/hid/hid-magicmouse.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index d5df2745f3da4..f4748db48967d 100644
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c
@@ -950,6 +950,22 @@ static void magicmouse_remove(struct hid_device *hdev)
 	hid_hw_stop(hdev);
 }
 
+#ifdef CONFIG_PM
+static int magicmouse_reset_resume(struct hid_device *hdev)
+{
+	struct magicmouse_sc *msc = hid_get_drvdata(hdev);
+
+	/* The device drops out of multitouch mode on resume; re-send the
+	 * enable report.  Only the HID_TYPE_USBMOUSE interface accepts it, and
+	 * it must be deferred. Sending it inline here is too early.
+	 */
+	if (msc && hdev->type == HID_TYPE_USBMOUSE)
+		schedule_delayed_work(&msc->work, msecs_to_jiffies(500));
+
+	return 0;
+}
+#endif
+
 static __u8 *magicmouse_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 				     unsigned int *rsize)
 {
@@ -1009,6 +1025,9 @@ static struct hid_driver magicmouse_driver = {
 	.event = magicmouse_event,
 	.input_mapping = magicmouse_input_mapping,
 	.input_configured = magicmouse_input_configured,
+#ifdef CONFIG_PM
+	.reset_resume = magicmouse_reset_resume,
+#endif
 };
 module_hid_driver(magicmouse_driver);
 
-- 
2.53.0