linux-kernel - Re: "Setting old previous keyboard state failed" error on Dell E7270

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Date:   Thu, 17 Nov 2016 13:19:16 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Matthew Garrett <mjg59@...f.ucam.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        gabriele.mzt@...il.com
Subject: Re: "Setting old previous keyboard state failed" error on Dell E7270

On Thursday 17 November 2016 12:27:33 Takashi Iwai wrote:
> Hi,
> 
> I noticed that a new machine I got yesterday, Dell Latitude E7270,
> always shows the error at boot time:
> 	dell_laptop: Setting old previous keyboard state failed
> 
>  From what I read from the code, it seems non-fatal.  But is it a way
> to "fix" it?
> 
> Or shouldn't we simply lower the printk level?
> 
> 
> thanks,
> 
> Takashi

Hi! Month ago I got private email about same problem reported by user. 
Looks like that Dell changed SMBIOS interface for keyboards and have not 
notified about it... User wrote that will do some research and write 
info to mailing list.

So in this case it is not non-fatal warning, but warning which telling 
us: "you are doing some operation which we do not know what is doing 
now...".

Masking this warning is not a good idea. There are only two good 
options:

1) Fix the code so it will work with that changed SMBIOS interface

2) Disable that code on problematic machines.

Anyway, keyboard backlight control in kernel is implemented from program 
smbios-keyboard-ctl provided and supported by Dell. I do not see any 
update to that program in upstream git repository.

http://github.com/dell/libsmbios/blob/master/src/bin/smbios-keyboard-ctl

So there are two options what could happen:

1) smbios-keyboard-ctl is working and kernel code not -- in this case 
bug in kernel, please provide debug logs from both smbios-keyboard-ctl 
and kernel and I could try to look at it

2) smbios-keyboard-ctl is not working too -- in this case please report 
bug to that libsmbios project and Dell needs to fix it

-- 
Pali Rohár
pali.rohar@...il.com

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