From 12df5d98b17f9f1748faa87260cd548b90da68df Mon Sep 17 00:00:00 2001
From: David Thurstenson <thurstylark@gmail.com>
Date: Mon, 5 Jun 2017 16:57:36 -0500
Subject: [PATCH] Added Keyboard Mapping page

---
 Keyboard Mapping.wiki | 74 +++++++++++++++++++++++++++++++++++++++++++
 index.wiki            |  3 +-
 2 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 Keyboard Mapping.wiki

diff --git a/Keyboard Mapping.wiki b/Keyboard Mapping.wiki
new file mode 100644
index 0000000..809bba1
--- /dev/null
+++ b/Keyboard Mapping.wiki	
@@ -0,0 +1,74 @@
+=Keyboard Mapping=
+References:
+* https://wiki.archlinux.org/index.php/Map_scancodes_to_keycodes
+* https://github.com/Earnestly/pkgbuilds/blob/master/system-config/hwdb-capslock-as-control.hwdb
+
+Maping keys is pretty simple, and if it's done at the udev level, it's universal, so it doesn't require any X or Wayland specific configuration.
+
+As an example, I map my compose key (menu key) to right meta (aka super, logo, windows, apple, or command key), and CapsLock to left Control.
+
+==Get Scancode==
+
+First, get the scancode(s) of the key(s) you wish to change. Easiest way is to use `evteest(1)`. For each keypress, you'll get information similar to the following:
+
+{{{class='prettyprint'
+Event: time 1496690003.603531, -------------- SYN_REPORT ------------
+Event: time 1496690003.723467, type 4 (EV_MSC), code 4 (MSC_SCAN), value 70065
+Event: time 1496690003.723467, type 1 (EV_KEY), code 127 (KEY_COMPOSE), value 0
+}}}
+
+The code you will need to use in the udev hwdb config file is the `MSC_SCAN` value (in this case: 70065).
+
+==Get Hardware ID==
+
+Next you will need the hardware Vendor and Product ids from `lsusb(1)`. These are two sets of four hexidecimal digits separated by a colon (:) printed right before the device name.
+
+{{{class='prettyprint'
+Bus 001 Device 005: ID 258a:1006 <keyboard name here>
+}}}
+
+In this example, the Vendor ID is `258a`, and the Product ID is `1006`.
+
+==Create udev hwdb Configuration==
+
+Then create `/etc/udev/hwdb.d/61-custom-keyboard.hwdb` with the following contents:
+
+{{{class='prettyprint'
+evdev:input:b0003v258Ap1006*
+ KEYBOARD_KEY_70065=rightmeta
+ KEYBOARD_KEY_70039=leftctrl
+}}}
+
+A few notes on the format of this file:
+* The format for the device identifying line for usb devices is `evdev:input:b0003v<Vendor ID>p<ProductID>*`. 
+	* If `<Product ID>` and `<Vendor ID>` contain letters, they must be capitalized
+	* These scancodes can be quite device-specific, so it is wise to be specific to *at least* the vendor and product IDs
+	* There are methods for identifying ata keyboards as well. Check the Arch Wiki page listed in the references above for more info
+* Defining a key to change is done with `KEYBOARD_KEY_<scancode>=<new keycode>`
+	* `<scancode>` is the code we pulled from evtest earlier
+	* `<new keycode>` is the keycode we want to emit when the key is pressed. Names of keycodes are listed in `/usr/include/linux/input-event-codes.h`, and should be all lowercased in your udev config.
+* The filename `61-custom-keyboard.hwdb` is somewhat arbitrary, but make sure that you order your file *after* the existing `60-keyboard.hwdb`.
+
+==Update Hardware Database Index==
+
+After changing the config files, the hwdb needs to be rebuilt:
+
+{{{class='prettyprint'
+# systemd-hwdb update
+}}}
+
+To start using this new hwdb, either reboot or tell udev to reload:
+
+{{{class='prettyprint'
+# udevadm trigger
+}}}
+
+Note that this will only work for adding or modifying existing key mappings. Deleted key mappings are kept in the kernel until a reboot.
+
+==Testing the New Mappings==
+
+A simple test can be run before trying the keys directly:
+
+{{{class='prettyprint'
+# udevadm info /dev/input/by-path/*-usb-*-kbd | grep KEYBOARD_KEY
+}}}
diff --git a/index.wiki b/index.wiki
index edf6bfd..51a8edc 100644
--- a/index.wiki
+++ b/index.wiki
@@ -10,7 +10,7 @@ Half brain dump, half documentation practice.
 * [[Automating Android App Builds]] -- Documentation of my setup for building AsteroidOS Sync from https://www.github.com/asteroidos/AsteroidOSSync
 * [[Audiobook RSS Feed]]
 
-===Dotfiles===
+===Configuration/Dotfiles===
 
 * [[Bashrc]]
 * Tmux
@@ -19,6 +19,7 @@ Half brain dump, half documentation practice.
 * [[Xinitrc]] -- Includes `srandrd` and X screen locker configuration
 * [[Pkglists]]
 * [[SSH]]
+* [[Keyboard Mapping]]
 
 ===Misc.===