sony laptop - keyboard backlight bizarre behaviour : not working on boot, working after sleep resume

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jopopo
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sony laptop - keyboard backlight bizarre behaviour : not working on boot, working after sleep resume

Post by jopopo » Mon Mar 05, 2018 6:53 pm

Hello, I would like to ask your help about the keyboard backlight of my sony vaio sve-1711x1e. dual boot mint 18.3 xfce/win7.

I tried to put everything in the title but here is more background story.

The keyboard backlight doesn't work on boot, but works perfectly fine when i resume from sleep.

Expected/normal behaviour : Like on seven : press any key and it lights on for a few seconds before fading out. There is no hardware key or switch to turn it on or off or change the keyboard backlight brightness btw.

It was working fine on ubuntu-studio 14.04, then started to have this bizarre behaviour on ubuntu-studio 16.04 and never stopped (tried it on ubuntu 17.04 as well).

Now on linux mint 18.3 it still has the same behaviour : the keyboard is lit on boot until the mint logo disapears, then it fades out and never turns on again.
If i enter sleep mode, and resume, then it will always work perfectly fine.

What I tried :

change /sys/module/sony_laptop/parameters from -1 to 1 as seen on another forum

create sony-laptop.conf with "options sony-laptop kbd_backlight=1" in modprobe.d as seen somewhere else

played with xset led commands as well.

no result.

I already asked this on a french mint forum, they didn't have a clue so one step further !

One last word : I am very new here, but I am not a kid, I have 5+ years of ubuntu behind me but I never had to ask anything on a linux forum, I'm not sure what to add here but please be kind to ask me any more info you'd need with the minimum direction on how to obtain them.
Please consider me a noob but I really want to learn, and I really want to fix this, even if I have to dig deep, I love this laptop.

Thank you very much for your reading and depending on the time zone, have a sweet night or a very good day.

Pheeble
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Re: sony laptop - keyboard backlight bizarre behaviour : not working on boot, working after sleep resume

Post by Pheeble » Sat Mar 17, 2018 8:25 pm

I don't have a Sony laptop, but a Toshiba. I had a similar problem for years until I found a solution online, but this was for a Toshiba Satellite laptop dual-booting Linux and Windows so it may not work for you.

In the case of Toshiba it seems the laptop's firmware may deliberately disable the keyboard backlight for non-Windows operating systems. A work-around was posted to the Linux kernel bugzilla page at https://bugzilla.kernel.org/show_bug.cgi?id=32742#c109. The method I used there was to boot the laptop with a Windows 7 installation DVD, do not proceed with Windows installation but exit the installation program (usually by clicking the 'X' in the top right corner) and reboot the computer. The keyboard backlighting then works in Linux until the next time Windows is booted, after which the whole process has to be repeated.

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Re: sony laptop - keyboard backlight bizarre behaviour : not working on boot, working after sleep resume

Post by jopopo » Mon Mar 19, 2018 5:39 pm

ok thank you very much for your reply this is a very strange thing this keyboard backlight, lots of people are having issues with it as i can see...
i just reinstalled windows 7 a few weeks ago i might have a try at this trick you mention i still have the usb stick ready... but i use windows when i want to play so this will be just for the sake of knowing if it works, i'm never doing this every time i load windows just for the keyboard backlight...

i would love to dig this out and find out especially why in my case is it fine after a suspend and not on boot, but i'm such a noob i can't really understand what to do...
nobody never heard of such a behaviour for devices working only after a suspend ? this might help.

Pheeble
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Re: sony laptop - keyboard backlight bizarre behaviour : not working on boot, working after sleep resume

Post by Pheeble » Mon Mar 19, 2018 7:17 pm

I haven't heard of the suspend issue before, but if - and this is a big 'if' - it is caused by the laptop's firmware, then it sort of makes sense.

The suspend state is managed by the BIOS firmware just as booting is. There is more information on power states in the Linux kernel at https://www.kernel.org/doc/Documentatio ... states.txt. The section on the S3 suspend-to-ram state says,
In particular, on ACPI systems the kernel passes control to the BIOS (platform firmware) as the last step during STR transitions and that usually results in powering down some more low-level components that aren't directly controlled by the kernel.
So if the firmware is written purely to work with Windows systems, as is usually the case, it may not work well with the Linux kernel instructions. It should, but hardware manufacturers generally provide zero Linux support, and sometimes they seem to take shortcuts in their code that take advantage of Windows quirks that don't apply in Linux.

While I have no knowledge of the proprietary code contained in the firmware, it's plausible that the power management code in the firmware creates the situation you are experiencing. Unfortunately, that's something that is impossible to check unless and until the firmware code is made open source, and I wouldn't want to hold my breath waiting for that.

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Re: sony laptop - keyboard backlight bizarre behaviour : not working on boot, working after sleep resume

Post by jopopo » Tue Mar 20, 2018 5:24 pm

thank you i was actually looking for something like a manual to help me understand how the kernel works, regarding this issue... i'm going to spend some time reading the link you provided and the rest of the manual.
i still believe i can make it work as it used to have no issue at all on ubuntu 12.04 and 14.04...
btw i posted this same thread on a global linux forum as well as on the french mint forum, i'll let you know here if i ever manage to solve this problem.

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