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>

Makefile.am

@@ -1,4 +1,4 @@
-SUBDIRS = src doc test tools
+SUBDIRS = src doc test tools udev
 
 ACLOCAL_AMFLAGS = -I m4 ${ACLOCAL_FLAGS}
 

configure.ac

@@ -69,6 +69,19 @@ fi
 AC_SUBST(GCC_CFLAGS)
 AC_SUBST(GCC_CXXFLAGS)
 
+udev_dir_default="$libdir/udev"
+AC_ARG_WITH(udev-dir,
+            AS_HELP_STRING([--with-udev-dir=DIR],
+                           [udev base directory [[default=$udev_dir_default]]]),
+            [],
+            [with_udev_dir="yes"])
+AS_CASE($with_udev_dir,
+	[no|""], [AC_MSG_ERROR([You must define a udev base directory])],
+	[yes], [udevdir="$udev_dir_default"],
+	[udevdir="$with_udev_dir"])
+UDEV_DIR=${udevdir}
+AC_SUBST(UDEV_DIR)
+
 AC_ARG_ENABLE([documentation],
 	      [AC_HELP_STRING([--enable-documentation],
 		              [Enable building the documentation (default=auto)])],
@@ -163,14 +176,15 @@ AC_CONFIG_FILES([Makefile
 		 src/libinput.pc
 		 src/libinput-version.h
 		 test/Makefile
-		 tools/Makefile])
+		 tools/Makefile
+		 udev/Makefile])
 AC_CONFIG_FILES([test/symbols-leak-test],
 		[chmod +x test/symbols-leak-test])
-
 AC_OUTPUT
 
 AC_MSG_RESULT([
 	Prefix			${prefix}
+	udev base dir		${UDEV_DIR}
 
 	Build documentation	${build_documentation}
 	Build tests		${build_tests}

udev/.gitignore

@@ -0,0 +1 @@
+libinput-device-group

udev/80-libinput-device-groups.rules

@@ -0,0 +1,8 @@
+ACTION!="add|change", GOTO="libinput_device_group_end"
+KERNEL!="event[0-9]*", GOTO="libinput_device_group_end"
+
+ATTRS{phys}=="?*", \
+	PROGRAM="libinput-device-group %S%p", \
+	ENV{LIBINPUT_DEVICE_GROUP}="%c"
+
+LABEL="libinput_device_group_end"

udev/Makefile.am

@@ -0,0 +1,9 @@
+udevdir=$(UDEV_DIR)
+udev_PROGRAMS = libinput-device-group
+
+libinput_device_group_SOURCES = libinput-device-group.c
+libinput_device_group_CFLAGS = $(LIBUDEV_CFLAGS) $(GCC_CFLAGS)
+libinput_device_group_LDADD = $(LIBUDEV_LIBS)
+
+udev_rulesdir=$(UDEV_DIR)/rules.d
+dist_udev_rules_DATA = 80-libinput-device-groups.rules

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;
+}