linux-kernel - [PATCH v2 1/2] Input: add input_set

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Date:   Thu,  2 Dec 2021 12:08:06 +0100
From:   José Expósito <jose.exposito89@...il.com>
To:     jikos@...nel.org
Cc:     benjamin.tissoires@...hat.com, peter.hutterer@...-t.net,
        roderick.colenbrander@...y.com, dmitry.torokhov@...il.com,
        pali@...nel.org, rydberg@...math.org, nick@...anahar.org,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        José Expósito <jose.exposito89@...il.com>
Subject: [PATCH v2 1/2] Input: add input_set_property()

Buttonpads are expected to map the INPUT_PROP_BUTTONPAD property bit
and the BTN_LEFT key bit.

As explained in the specification, where a device has a button type
value of 0 (click-pad) or 1 (pressure-pad) there should not be
discrete buttons:
https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/touchpad-windows-precision-touchpad-collection#device-capabilities-feature-report

However, some drivers map the BTN_RIGHT and/or BTN_MIDDLE key bits even
though the device is a buttonpad and therefore does not have those
buttons.

This behavior has forced userspace applications like libinput to
implement different workarounds and quirks to detect buttonpads and
offer to the user the right set of features and configuration options.
For more information:
https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/726

In order to avoid this issue add a helper function for drivers to add
device properties and make sure that the conditions associated with the
INPUT_PROP_BUTTONPAD property are meet.

Notice that this change will not affect udev because it does not check
for buttons. See systemd/src/udev/udev-builtin-input_id.c.

List of known affected hardware:

 - Chuwi AeroBook Plus
 - Chuwi Gemibook
 - Framework Laptop
 - GPD Win Max
 - Huawei MateBook 2020
 - Prestigio Smartbook 141 C2
 - Purism Librem 14v1
 - StarLite Mk II   - AMI firmware
 - StarLite Mk II   - Coreboot firmware
 - StarLite Mk III  - AMI firmware
 - StarLite Mk III  - Coreboot firmware
 - StarLabTop Mk IV - AMI firmware
 - StarLabTop Mk IV - Coreboot firmware
 - StarBook Mk V

Signed-off-by: José Expósito <jose.exposito89@...il.com>
---
 drivers/input/input.c | 35 +++++++++++++++++++++++++++++++++++
 include/linux/input.h |  1 +
 2 files changed, 36 insertions(+)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index ccaeb2426385..f7e23b3b6ae5 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -2125,6 +2125,41 @@ void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int
 }
 EXPORT_SYMBOL(input_set_capability);
 
+/**
+ * input_set_property - add a property to the device
+ * @dev: device to add the property to
+ * @property: type of the property (INPUT_PROP_POINTER, INPUT_PROP_DIRECT...)
+ *
+ * In addition to setting up corresponding bit in dev->propbit the function
+ * might add or remove related capabilities.
+ */
+void input_set_property(struct input_dev *dev, unsigned int property)
+{
+	switch (property) {
+	case INPUT_PROP_POINTER:
+	case INPUT_PROP_DIRECT:
+	case INPUT_PROP_SEMI_MT:
+	case INPUT_PROP_TOPBUTTONPAD:
+	case INPUT_PROP_POINTING_STICK:
+	case INPUT_PROP_ACCELEROMETER:
+		break;
+
+	case INPUT_PROP_BUTTONPAD:
+		input_set_capability(dev, EV_KEY, BTN_LEFT);
+		__clear_bit(BTN_RIGHT, dev->keybit);
+		__clear_bit(BTN_MIDDLE, dev->keybit);
+		break;
+
+	default:
+		pr_err("%s: unknown property %u\n", __func__, property);
+		dump_stack();
+		return;
+	}
+
+	__set_bit(property, dev->propbit);
+}
+EXPORT_SYMBOL(input_set_property);
+
 static unsigned int input_estimate_events_per_packet(struct input_dev *dev)
 {
 	int mt_slots;
diff --git a/include/linux/input.h b/include/linux/input.h
index 0354b298d874..5f357687da42 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -456,6 +456,7 @@ static inline void input_mt_sync(struct input_dev *dev)
 }
 
 void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code);
+void input_set_property(struct input_dev *dev, unsigned int property);
 
 /**
  * input_set_events_per_packet - tell handlers about the driver event rate
-- 
2.25.1