linux-kernel - [PATCH 2/4] HID: magicmouse: fix 3 button emulation of Mouse 2

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Date:   Sat, 27 Mar 2021 21:05:06 +0800
From:   John Chen <johnchen902@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Rohit Pidaparthi <rohitpid@...il.com>,
        RicardoEPRodrigues <ricardo.e.p.rodrigues@...il.com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        John Chen <johnchen902@...il.com>
Subject: [PATCH 2/4] HID: magicmouse: fix 3 button emulation of Mouse 2

It is observed that, with 3 button emulation, when middle button is
clicked, either the left button or right button is clicked as well. It
is caused by hidinput "correctly" acting on the event, oblivious to the
3 button emulation.

As raw_event has taken care of everything, no further processing is
needed. However, the only way to stop at raw_event is to return an error
(negative) value. Therefore, the processing is stopped at event instead.

Signed-off-by: John Chen <johnchen902@...il.com>
---
 drivers/hid/hid-magicmouse.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index 7aad6ca56780..c646b4cd3783 100644
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c
@@ -440,6 +440,21 @@ static int magicmouse_raw_event(struct hid_device *hdev,
 	return 1;
 }
 
+static int magicmouse_event(struct hid_device *hdev, struct hid_field *field,
+		struct hid_usage *usage, __s32 value)
+{
+	struct magicmouse_sc *msc = hid_get_drvdata(hdev);
+	if (msc->input->id.product == USB_DEVICE_ID_APPLE_MAGICMOUSE2 &&
+	    field->report->id == MOUSE2_REPORT_ID) {
+		// magic_mouse_raw_event has done all the work. Skip hidinput.
+		//
+		// Specifically, hidinput may modify BTN_LEFT and BTN_RIGHT,
+		// breaking emulate_3button.
+		return 1;
+	}
+	return 0;
+}
+
 static int magicmouse_setup_input(struct input_dev *input, struct hid_device *hdev)
 {
 	int error;
@@ -754,6 +769,7 @@ static struct hid_driver magicmouse_driver = {
 	.id_table = magic_mice,
 	.probe = magicmouse_probe,
 	.raw_event = magicmouse_raw_event,
+	.event = magicmouse_event,
 	.input_mapping = magicmouse_input_mapping,
 	.input_configured = magicmouse_input_configured,
 };
-- 
2.31.0