Re: Keyboard backlight not working on my NP900X5N laptop

From: Jan Vlietland
Date: Fri Jan 04 2019 - 11:17:42 EST

Hi Darren,

I understand your extra workload. For me it is just being another user complaining about some bug. Sorry for that :-) Good to know the response time. I will keep that in mind.

Anyway. I have changed the static variable to "0A", recompiled the module and I get the same output 'no such device'.

However I am now running in EFI mode based on another bug:

...and I see in the code....

ÂÂÂ struct samsung_laptop *samsung;
ÂÂÂ int ret;

ÂÂÂ if (efi_enabled(EFI_BOOT))

ÂÂÂ quirks = &samsung_unknown;
ÂÂÂ if (!force && !dmi_check_system(samsung_dmi_table))

ÂÂÂ samsung = kzalloc(sizeof(*samsung), GFP_KERNEL);
ÂÂÂ if (!samsung)

Is that EFI restriction still valid. As far as I remember Samsung repaired their BIOS. Or does the driver not work in EFI mode anyway?

On 03-01-19 03:03, Darren Hart wrote:
On Mon, Dec 31, 2018 at 08:40:43PM +0100, Jan Vlietland wrote:
Hi all,

Hey Jan,

Greg K-H suggested to mail you guys.

I installed Linux 4.20.0-rc7 (downloaded, compiled and installed) on a Samsung NP900X5N laptop and have noticed 3 bugs. 2 of them I found in Bugzilla and replied on them (i915 and Nouveau issues). I am currently discussing them with an intel engineer.

On other bug I haven't found so therefore a mail directly to you guys as maintainers.

On my other machine, a Samsung NP900X4D (just bought it in the USA, 2017 model), the samsung-laptop.ko module is enabling the use of the keyboard backlight keys.

It is not working on my new machine NP900X5N. My samsung-laptop.ko driver isn't loading. If I try to load it manually it complains about 'no such device".

My Linux kernel is working in CSM mode. The module is still not loaded.

That's correct.

As it is weekend I did some more reading and debugging of the module. To my understanding the module checks the model and type of the laptop. The known models and types are stored in the struct:

static struct dmi_system_id __initdata samsung_dmi_table[]

I wondr if the NP900X5N notebook is included in this list.

With dmidecode -t chassis it shows:
Getting SMBIOS data from sysfs.
SMBIOS 3.0.0 present.

Handle 0x0003, DMI type 3, 22 bytes
Chassis Information
Type: Notebook
Lock: Not Present
Version: N/A
Serial Number: 0F4C91CJ900346
Asset Tag: No Asset Tag
Boot-up State: Safe
Power Supply State: Safe
Thermal State: Other
Security Status: None
OEM Information: 0x00000000
Height: Unspecified
Number Of Power Cords: 1
Contained Elements: 0
SKU Number: Chassis

If I use the -u flag. The notebook value is 0x0A, not 0x10!!!

Could that be the reason for not loading?
Seems likely.

.matches = {
DMI_MATCH(DMI_CHASSIS_TYPE, "10"), /* Notebook */

Maybe another reason could that that either the i915 and Nouveau modules are
not working well. I get black screens with the i915 and MMIO faults with the
nouveau driver. That is another issue that I need to tackle.

I would expect a different error than "no such device" in that case.
I think your first thought was correct.

As a simple test, I'd suggest replacing "10" with "0A" in the existing
DMI_CHASSIS_TYPE match, recompile, and see if it loads and works
correctly. Would you be able to test this?

Oh happy new year :-)

Happy New Year!