Add udev bits to assign LIBINPUT_DEVICE_GROUP

The easiest way to get a device group is by looking at the phys path of the
input device (which looks like usb-0000:00:14.0-1/input1) and dropping the
/inputX bit. The rest is the same for devices that belong together (except on
the Cintiq 22HD Touch).

Ideally we could just take ATTRS{phys} but we can't select substrings to drop
into ENV so we need to do it ourselves. This patch adds a callout that takes a
syspath and prints the mangled path, to be used in LIBINPUT_DEVICE_GROUP.

The rule triggers on any device that has a non-zero phys attribute, this
groups devices like tablets together but also devices like mice with multiple
interfaces.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Tested-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/udev/libinput-device-group.c b/udev/libinput-device-group.c
new file mode 100644
index 0000000..50bfbe0
--- /dev/null
+++ b/udev/libinput-device-group.c
@@ -0,0 +1,77 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <libudev.h>
+
+int main(int argc, char **argv)
+{
+	int rc = 1;
+	struct udev *udev = NULL;
+	struct udev_device *device = NULL;
+	const char *syspath,
+	           *phys = NULL;
+	char *group,
+	     *str;
+
+	if (argc != 2)
+		return 1;
+
+	syspath = argv[1];
+
+	udev = udev_new();
+	if (!udev)
+		goto out;
+
+	device = udev_device_new_from_syspath(udev, syspath);
+	if (!device)
+		goto out;
+
+	/* Find the first parent with ATTRS{phys} set. For tablets that
+	 * value looks like usb-0000:00:14.0-1/input1. Drop the /input1
+	 * bit and use the remainder as device group identifier */
+	while (device != NULL) {
+		struct udev_device *parent;
+
+		phys = udev_device_get_sysattr_value(device, "phys");
+		if (phys)
+			break;
+
+		parent = udev_device_get_parent(device);
+		udev_device_ref(parent);
+		udev_device_unref(device);
+		device = parent;
+	}
+
+	if (!phys)
+		goto out;
+
+	group = strdup(phys);
+	if (!group)
+		goto out;
+
+	str = strstr(group, "/input");
+	if (str)
+		*str = '\0';
+
+	/* Cintiq 22HD Touch has
+	   usb-0000:00:14.0-6.3.1/input0 for the touch
+	   usb-0000:00:14.0-6.3.0/input0 for the pen
+	   Check if there's a . after the last -, if so, cut off the string
+	   there.
+	  */
+	str = strrchr(group, '.');
+	if (str && str > strrchr(group, '-'))
+		*str = '\0';
+
+	printf("%s\n", group);
+	free(group);
+
+	rc = 0;
+out:
+	if (device)
+		udev_device_unref(device);
+	if (udev)
+		udev_unref(udev);
+
+	return rc;
+}