Lenovo touchpad not working on Debian 9

Question

I have a Lenovo IdeaPad 320-15AST and I have Debian on it but the touchpad is not working and on my xinput list is not listed any touchpad:

xinput list
⎡ Virtual core pointer                           id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                 id=4    [slave  pointer  (2)]
⎣ Virtual core keyboard                          id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]                                                                                                                   
    ↳ Power Button                              id=6    [slave  keyboard (3)]                                                                                                                   
    ↳ Video Bus                                 id=7    [slave  keyboard (3)]                                                                                                                   
    ↳ Power Button                              id=8    [slave  keyboard (3)]                                                                                                                   
    ↳ EasyCamera                                id=9    [slave  keyboard (3)]                                                                                                                   
    ↳ Ideapad extra buttons                     id=10   [slave  keyboard (3)]                                                                                                                   
    ↳ AT Translated Set 2 keyboard              id=11   [slave  keyboard (3)]

But works perfectly on Windows.  It's a Synaptic touchpad. 

Answer 1

It seems you need kernel 4.14 or newer, see https://bugzilla.kernel.org/show_bug.cgi?id=196985 or this post on the lenovo forums.

You can try to install the latest kernel 4.19.16-1 from the backports repository.

You need to run the following commands as root.

1. Add repository entry for stretch-backports in /etc/apt/sources.list

   echo "deb http://ftp.debian.org/debian stretch-backports main" >> /etc/apt/sources.list
   

2. Update package index

   apt-get update
   

3. Install new kernel

   apt-get -t stretch-backports install linux-image-amd64
   

4. Optional: install kernel-header files

   apt-get -t stretch-backports install linux-headers-amd64
   

5. Reboot

   reboot
   

If it doesn't work you can still boot your old kernel from the "Advanced options" boot menu.

Answer 2

Some new touchpads can be detected through the PS/2 interface, but their main functionality is available only through SMBus.

Debian 9's standard kernel might be just slightly too old to support those: you might need a kernel that has the compile-time option CONFIG_MOUSE_PS2_SYNAPTICS_SMBUS for them. Maybe try the backport kernels?

Or if your kernel does have the synaptics-rmi4 kernel module, try loading the appropriate I2C/SMBus drivers for your system and then loading synaptics-rmi4.

(Looks like the support for SMBus-connected touchpads was starting to be added at kernel version 4.8. or so, and Debian 9's standard kernel is 4.9.x, so the SMBus touchpad support might have been still incomplete or undergoing significant tweaking in that kernel version.)