udev: builtin-keyboard: add support for EVDEV_ABS_*

Parse properties in the form
EVDEV_ABS_00="<min>:<max>:<res>:<fuzz>:<flat>"

and apply them to the kernel device. Future processes that open that device
will see the updated EV_ABS range.

This is particularly useful for touchpads that don't provide a resolution in
the kernel driver but can be fixed up through hwdb entries (e.g. bcm5974).

All values in the property are optional, e.g. a string of "::45" is valid to
set the resolution to 45.

The order intentionally orders resolution before fuzz and flat despite it
being the last element in the absinfo struct. The use-case for setting
fuzz/flat is almost non-existent, resolution is probably the most common case
we'll need.

To avoid multiple hwdb invocations for the same device, replace the
hwdb "keyboard:" prefix with "evdev:" and drop the separate 60-keyboard.rules
file. The new 60-evdev.rules is called for all event nodes
anyway, we don't need a separate rules file and second callout to the hwdb
builtin.

1 files changed, 37 insertions, 0 deletions

diff --git a/hwdb/60-evdev.hwdb b/hwdb/60-evdev.hwdb
new file mode 100644
index 0000000000..ad2d09e721
--- /dev/null
+++ b/hwdb/60-evdev.hwdb
@@ -0,0 +1,37 @@
+# This file is part of systemd.
+#
+# The lookup keys are composed in:
+#   60-evdev.rules
+#
+# Note: The format of the "evdev:" prefix match key is a
+# contract between the rules file and the hardware data, it might
+# change in later revisions to support more or better matches, it
+# is not necessarily expected to be a stable ABI.
+#
+# Match string formats:
+# evdev:<modalias>
+# evdev:name:<device name>:dmi:<dmi string>
+#
+# To add local entries, create a new file
+#   /etc/udev/hwdb.d/61-evdev-local.hwdb
+# and add your rules there. To load the new rules execute (as root):
+#   udevadm hwdb --update
+#   udevadm trigger /dev/input/eventXX
+# where /dev/input/eventXX is the device in question. If in
+# doubt, simply use /dev/input/event* to reload all input rules.
+#
+# If your changes are generally applicable, open a bug report on
+#   http://bugs.freedesktop.org/enter_bug.cgi?product=systemd
+# and include your new rules, a description of the device, and the
+# output of
+#   udevadm info /dev/input/eventXX
+# (or /dev/input/event*).
+#
+# Allowed properties are:
+#    EVDEV_ABS_<axis>=<min>:<max>:<res>:<fuzz>:<flat>
+#
+# where <axis> is the hexadecimal EV_ABS code as listed in linux/input.h
+# and min, max, res, fuzz, flat are the decimal values to the respective
+# fields of the struct input_absinfo as listed in linux/input.h.
+# If a field is missing the field will be left as-is. Not all fields need to
+# be present. e.g. ::45 sets the resolution to 45 units/mm.