udev: keyboard-builtin: Add support for setting IBM trackpoint sensitivity

IBM / Lenovo trackpoints allow specifying a sensitivity setting through a
ps/2 command, which changes the range of the deltas sent when using the
trackpoint.

On some models with normal usage only deltas of 1 or 2 are send, resulting in
there only being 2 mouse cursor movement speeds, rather than the expected fluid
scale. Changing the sensitivity to a higher level than the bootup default fixes
this.

This commit adds support for setting a POINTINGSTICK_SENSITIVITY value
in hwdb to allow changing the sensitivity on boot through udev / hwdb.

2 files changed, 40 insertions, 0 deletions

diff --git a/hwdb/70-pointingstick.hwdb b/hwdb/70-pointingstick.hwdb
index 9fd5fb886a..e87d753339 100644
--- a/hwdb/70-pointingstick.hwdb
+++ b/hwdb/70-pointingstick.hwdb
@@ -41,6 +41,7 @@
 #
 # Allowed properties are:
 #   POINTINGSTICK_CONST_ACCEL
+#   POINTINGSTICK_SENSITIVITY
 #
 #########################################
 #      POINTINGSTICK_CONST_ACCEL        #
@@ -53,6 +54,17 @@
 # by how much to multiply deltas generated by the pointingstick to get
 # normalized deltas.
 #
+#########################################
+#      POINTINGSTICK_SENSITIVITY        #
+#########################################
+#
+# TPPS/2 IBM TrackPoint driver sensitivity sysfs setting
+#    POINTINGSTICK_SENSITIVITY=<sensitivity>
+#
+# Where <sensitivity> is a number between 0 and 255, note this property
+# only applies to TPPS/2 IBM TrackPoint devices, see
+# drivers/input/mouse/trackpoint.c in the Linux kernel sources.
+#
 
 #
 # Sort by by brand, model
diff --git a/src/udev/udev-builtin-keyboard.c b/src/udev/udev-builtin-keyboard.c
index c7f7f84afd..b6da734a3c 100644
--- a/src/udev/udev-builtin-keyboard.c
+++ b/src/udev/udev-builtin-keyboard.c
@@ -146,6 +146,32 @@ static void override_abs(int fd, const char *devnode,
                 log_error_errno(errno, "Unable to EVIOCSABS device \"%s\"", devnode);
 }
 
+static void set_trackpoint_sensitivity(struct udev_device *dev, const char *value)
+{
+        struct udev_device *pdev;
+        char val_s[DECIMAL_STR_MAX(int)];
+        int r, val_i;
+
+        /* The sensitivity sysfs attr belongs to the serio parent device */
+        pdev = udev_device_get_parent_with_subsystem_devtype(dev, "serio", NULL);
+        if (!pdev) {
+                log_warning("Failed to get serio parent for '%s'", udev_device_get_devnode(dev));
+                return;
+        }
+
+        r = safe_atoi(value, &val_i);
+        if (r < 0) {
+                log_error("Unable to parse POINTINGSTICK_SENSITIVITY '%s' for '%s'", value, udev_device_get_devnode(dev));
+                return;
+        }
+
+        xsprintf(val_s, "%d", val_i);
+
+        r = udev_device_set_sysattr_value(pdev, "sensitivity", val_s);
+        if (r < 0)
+                log_error_errno(r, "Failed to write 'sensitivity' attribute for '%s': %m", udev_device_get_devnode(pdev));
+}
+
 static int open_device(const char *devnode) {
         int fd;
 
@@ -223,6 +249,8 @@ static int builtin_keyboard(struct udev_device *dev, int argc, char *argv[], boo
                         }
 
                         override_abs(fd, node, evcode, udev_list_entry_get_value(entry));
+                } else if (streq(key, "POINTINGSTICK_SENSITIVITY")) {
+                        set_trackpoint_sensitivity(dev, udev_list_entry_get_value(entry));
                 }
         }