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+# /dev/tictactoe
+
+A Linux driver for a character device which can be used to play
+[Tic-tac-toe](https://en.wikipedia.org/wiki/Tic-tac-toe).
+
+## Usage
+
+*Disclaimer:* I make no guarantees about the soundness of the driver code.
+Use with caution (i.e. only in a virtual machine).
+
+### Building
+
+Clone this repository, `cd` to it, then run `make`.
+
+### Loading
+
+After building the module, run `insmod tictactoe.ko` as root to load it.
+
+### Using the device
+
+After loading the module, player X can write grid coordinates
+(ranging from 1 to 3, format `XY`) to `/dev/tictactoe` to make their first move:
+
+```console
+# echo 12 > /dev/tictactoe
+```
+
+After player X has made his move, player O can do the same:
+
+```console
+# echo 22 > /dev/tictactoe
+```
+
+To inspect the current state of the game, simply read from `/dev/tictactoe`:
+
+```console
+# cat /dev/tictactoe
+```
+
+```
+#####
+# X #
+# O #
+#   #
+#####
+
+It's X's turn!
+```
+
+Alternatively, you can `watch` the file in a separate terminal for automatic
+updating:
+
+```console
+# watch -n 0.5 cat /dev/tictactoe
+```
+
+To start a new game, write `reset` to `/dev/tictactoe`:
+
+```console
+# echo reset > /dev/tictactoe
+```
+
+### Unloading
+
+Run `rmmod tictactoe` as root to unload the module.