Here’s how to get hardware control with much less effort / time by building an in-tree kernel module.
Install the 4.9 kernel, headers and source. At the moment this is a meta package for linux-image-4.9.0-8, or the 4.9.110-3 kernel. This may bump in the future
sudo apt install linux-image-amd64 linux-headers-$(uname -r) linux-source \
gcc make libc6-dev binutils-dev bc
Verify that the current kernel is 4.9.0-8-amd64 with uname -r
If it isn’t, update the grub bootloader to select the correct menuentry by setting the grub default.
Prepare kernel build directory and extract the source
mkdir ~/kbuild && cd ~/kbuild
tar xf /usr/src/linux-source-4.9.tar.xz
cd linux-source-4.9
Get the module symvers from the headers. This file is generated when you build the full kernel, so we save a few hours by skipping this.
cp /usr/src/linux-headers-$(uname -r)/Module.symvers .
Get the corresponding kernel config
cp /boot/config-$(uname -r) .config
Verify if the kernel source version matches the current version.
uname -r
make kernelversion
If these previous commands did not match, edit the first lines of the Makefile like this. (thanks @neversaydie)
SUBLEVEL = 0
EXTRAVERSION = -8-amd64
Enable the Intel LPSS UART driver in the kernel config.
Directly with an editor
Enable these 2 parameters in the .config in your favorite editor
CONFIG_SERIAL_8250_LPSS=m
CONFIG_DW_DMAC_PCI=m
Note that these parameters may change in future kernels.
or select it in the menu
sudo apt install libncurses5-dev
make nconfig
Enable support as a module.
-> Device Drivers
-> Character devices
-> Serial drivers
-> <M> Support for serial ports on Intel LPSS platforms.
Save and exit.
Now compile the module
make prepare
make modules_prepare
make M=scripts/mod
make M=drivers/tty/serial
And install it
sudo make M=drivers/tty/serial modules_install
sudo depmod
sudo modprobe 8250_lpss
Verify it’s active
lsmod | grep 8250_lpss
This lighter module is easier to keep in sync with the mainline kernel.
All that’s left is to put all this in a post-install script.
