At some point in the 18.04 cycle, /sys/bus/iio has disappeared from my system

Bug #1807250 reported by Nish Aravamudan on 2018-12-06

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This bug affects 1 person
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
linux-hwe (Ubuntu)

Bug Description

I have a Yoga 900-13ISK and a Thinkpad T470s. Both have had working screen rotation in the past. However, I noticed today while supporting a user in #ubuntu, neither do now. No icon in the Gnome menu and:

# G_MESSAGES_DEBUG=all iio-sensor-proxy
** (process:14877): DEBUG: 12:31:21.603: Could not find any supported sensors

Indeed, /sys/bus/iio does not exist! I believe this is distinct from LP: #1792813, as I have just tested mainline 4.19 and it also does not work.

I am working on getting more data, including testing older kernels from 18.04, but it might take me some time.

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 1807250

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.

Changed in linux (Ubuntu):
status: New → Incomplete
tags: added: bionic
Nish Aravamudan (nacc) wrote :

Right, I understand fully what the bot is asking for, but it's not exactly relevant here. We are seeing (on at least two systems) a lack of IIO device discovery. If I modprobe all the iio modules, I do get a /sys/bus/iio, but no devices in it. So it feels like something is missing, but I don't know where.

Changed in linux (Ubuntu):
status: Incomplete → Confirmed
Nish Aravamudan (nacc) wrote :

I just tried booting into 4.15.0-20 as the release pocket has it still and it also failed to work. So now I'm wondering if/when it did work. I will try and narrow it down in the next few days.

Your full name (wzpdqbty) wrote :

Yeah, so this is like the person who started complaining about this stuff which was totally confirmed by nacc.

Exceedingly fun fact: current bionic userspace/install booted with debian stable kernel 4.9, debian testing kernel 4.18 and ye olde xenial 4.4.0-134 is working just fine *indicating* that support for an entire bus class has been missing/faulty in ubuntu >=4.15 since bionic launch like way back before everyone knew the name Cambridge Analytica and that girl with the weird teeth from "Smallville" was charged with human trafficking or whatever. I realize that people have selfies to take and like totally have to spend a lot of time placating their friends about their issues and stuff but that no one noticed this until now is kinda disturbing and I like totally have to resist the urge to somehow implicate Kylie Jenner in this.

The reason for the attitude is that i had to complete a friggin js-required Scroogle puzzle to state the obvious.

Your full name (wzpdqbty) wrote :

The sad state of being able to use Ubuntu on touch devices (hint: you can't)

So, apparently support for an entire bus class has been missing since ubuntu bionic (18.04 LTS) was released in april. Using kernels from other distros or ubuntus old xenial 4.4.0-134 all provide access to sensor data, suggesting the issue is with current (and shipped) kernels. Three weeks into this not much is happening even though the issue also affect canonical-specific 4,18 kernels.

This all suggests that pretty much no one has been using ubuntu on touch devices otherwise i wouldn't be the first one to notice this. Now that the devs know this they have no time for it...

Your full name (wzpdqbty) wrote :

The issue now appears resolved with hwe-18.04/4.18.0-13, /sys/bus/iio is now present and the functionality has been restored.

/sys/bus/iio appears to be missing on all the bionic 4.15.* kernel releases (including 4.15.0-43) but is present on xenial 4.4 and cosmic 4.18 (at least as of 4.18.0-13). Here is to hoping there is not a similar kerfuffle with RNGs and stuff :P

Kai-Heng Feng (kaihengfeng) wrote :

Please find the first -rc kernel that fixes the issue between v4.15 and v4.18.
Kernels can be downloaded at [1].


Daniel van Vugt (vanvugt) wrote :

Incomplete: Someone please answer comment #7.

Changed in linux-hwe (Ubuntu):
status: New → Confirmed
no longer affects: gdm3 (Ubuntu)
Changed in linux (Ubuntu):
status: Confirmed → Incomplete
Changed in linux-hwe (Ubuntu):
status: Confirmed → Incomplete
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