Tablet Mode

"External Kernel module for 2-in-1 hybrid laptop"

It detects according to accelerometers's calibration datas, if the laptop is in tablet position. Consequently, it disables the internal keyboard and trackpad.

Information:

• Built for kernel v4.19.40
• Tested with accelerometers handled by the kxcjk1013 driver

Build

As External Module

Build the module with the following command:

$ make KDIR=<path/to/kernel/tree/source>

As Internal Module

This is an example:

1. Copy this repository as module directory into the kernel source tree. Let's say into the drivers/input/ subdirectory.

2. Integrate the tabletmod's Kconfig file into those of the drivers/input/ (c.f Kconfig section). Add the following line in to the drivers/input/Kconfig file:

source "drivers/input/tabletmod/Kconfig"

3. Add this module to the building chain, by adding the following line to the drivers/input/Makefile file:

obj-$(CONFIG_TABLET_MODE) += tabletmod/

4. Go to the kernel tree's root and run the make command

Kconfig

A Kconfig file is available if you would like to integrate this module with the kernel's configuration tree structure (c.f Documentation/kbuild/kconfig-language.txt).

Run

Once installed, you can run the module as following:

# modprobe tabletmod [debug=1]

The debug option enables the debugging messages.

Development

Add the module to initramfs

Add the module name with its options to the /etc/initramfs-tools/modules file with the following command:

# echo "tabletmod debug=1" > /etc/initramfs-tools/modules

On Debian system, update the current kernel's initramfs (c.f uname -r) as following:

# update-initramfs -u

For futher information, read the man page.

DMI-based module autoloading

How to autoload this module for specific platforms ?

The idea is to load laptop drivers automatically (and other drivers which cannot be autoloaded otherwise), based on the DMI system identification information of the BIOS. We use the MODULE_ALIAS(_dmi_) macro to autoload this module according to a given _dmi_ modalias.

Here is an extract from tabletmod.c where we use the product name (pv) and the board name (rn) to identify the "Ordissimo Julia 2" platform. The * wildcard card means it will match anything. Note that the information are seperated by : colon character:

[...]
// Platform: Ordissimo Julia 2
MODULE_ALIAS("dmi:bvn*:bvr*:bd*:svn*:pnGeoFlex3:pvr*:rvn*:rnS133AR700:*");
[...]

This is a description of all the fields :

bvn: BIOS Vendor  | svn: System Vendor   | rvn: Board Vendor  | cvn: Chassis Vendor
bvr: BIOS Version | pn:  Product Name    | rn:  Board Name    | ct:  Chassis Type
bd:  BIOS Date    | pvr: Product Version | rvr: Board Version | cvr: Chassis Version

The following command prints the complete modalias to match the current platform:

$ cat /sys/devices/virtual/dmi/id/modalias

For instance, the following DMI modalias matchs all profiles leveraging the * wildcard character:

dmi:bvn*:bvr*:bd*:svn*:pn*:pvr*:rvn*:rn*:rvr*:cvn*:ct*:cvr*

How to test a DMI modalias ?

Create a .hwdb file which will contain the machine's entire modalias to test:

# printf "%s\n FAKE_PROPERTY=ok\n" "<full-modalias>" \
	> /lib/udev/hwdb.d/99-tabletmod.hwdb

Update the hardware database with the following command:

# systemd-hwdb update

Verify if the given modalias matchs with existing one:

# systemd-hwdb query '<modalias>'

<modalias>
FAKE_PROPERTY=ok

No output if it doesn't match:

# systemd-hwdb query '<bad_modalias>'   (no output if no match)