Additional initializer needed to recognize trackpad on Lenovo Yoga 720 laptop

[Mike Schwartz]

There's just a 1 line patch required, to add an initializer to array of structs scanned to match up the device ID with driver.

The PR is here:

https://github.com/torvalds/linux/pull/444#discussion_r131229815

I've applied the patch and created and booted from a custom kernel and it works great.

The laptop is wonderful running Ubuntu: I7 7700HQ, 16G RAM, 500G SSD, 4K touch screen, decent I/O ports.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1710392

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Mike Schwartz (mykesx)]

I searched the WWW for any kind of solution to the trackpad not being recognized. There are several months of similar questions, but no resolution. Until this patch was made public/known.

Further discussion here:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1700657

[Joseph Salisbury (jsalisbury)]

Did this issue start happening after an update/upgrade? Was there a prior kernel version where you were not having this particular problem?

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.13 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.13-rc4

[Mike Schwartz (mykesx)]

No.

The laptop is a 2017 model. The source file in question simply doesn't have an array element that describes/identifies the trackpad. My assumption is that the driver maintainer simply hasn't seen a device with this ID before.

I would be happy to test the latest kernel, but I don;'t see the required fix in the source code.

https://github.com/torvalds/linux/blob/master/drivers/mfd/intel-lpss-pci.c#L223

(the missing line is after that one)

If this is not the correct kernel source, please let me know. This is master/4.13-rc3 branch.

[Mike Schwartz (mykesx)]

Sorry, to answer the first question, the latest kernels do boot on the machine, the trackpad isn't recognized and doesn't respond to anything at all.

[Mike Schwartz (mykesx)]

The bug exists upstream in 4.13-rc4

[Mike Schwartz (mykesx)]

I changed it to confirmed, although I am the reporter.

I found the patch is missing in the ubuntu kernel source:

https://git.launchpad.net/~ubuntu-kernel-test/ubuntu/+source/linux/+git/mainline-crack/tree/drivers/mfd/intel-lpss-pci.c

[Mike Schwartz (mykesx)]

http://kernel.ubuntu.com/git/kernel-ppa/mirror/linux.git/tree/drivers/mfd/intel-lpss-pci.c

Looks like the source is now fixed.