msi-ec: add Cyborg 15 B2RW and MS-1606 backlight support

[ItsVaidas]

close #647
close #726
close #762

Note:
There are 3 models:
RGB:
https://www.msi.com/Laptop/Cyborg-15-B13WX
https://www.msi.com/Laptop/Cyborg-15-B2RWX
White keyboard:
https://www.msi.com/Business-Productivity/VenturePro-15-A2RWX

They probably have different EC revision. In this case - single color controller is enabled in EC and banned in whitelist.

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What changed

• add 15Q3EMS1.108 firmware support for Cyborg 15 B2RWEKG/B2RWGKG
• add a HID driver for the laptop's 0db0:1606 MSI MysticLight MS-1606 controller
• expose the controller as msi::kbd_backlight with levels 0 through 4
• suppress the non-functional EC keyboard-backlight interface on this firmware
• include the HID module in regular and DKMS installation paths

Why

On this generation, EC register 0xd3 is only a status mirror. Writes update
the register but do not change the physical keyboard. The keyboard lighting is
controlled by a dedicated USB HID device.

The MS-1606 does not provide a separate brightness command or useful RGB
readback. The driver therefore scales a configurable fixed RGB color in the
steady-effect packet. The default 255:50:0 color can be changed with the
color_red, color_green, and color_blue module parameters.

Validation

• tested all five brightness states on MSI Cyborg 15 B2RWGKG
• verified the MS-1606 HID report sequence against MSI Center's four-zone implementation
• built against 7.1.5-1-cachyos with Clang
• checkpatch.pl --strict: zero errors, warnings, or checks
• installed and exercised through DKMS and the Linux LED sysfs interface

[glpnk]

AI?

[glpnk]

Where you got Mystic Light code? You should remove it, because it's not related to project. Keep only EC version you want to add

[ItsVaidas]

Well, on my laptop trying to control the backlight via current msi-ec method fails miserably. So I thought maybe a fix is needed specifically for my type of laptops? With this fix Linux correctly recognizes the 5 stage backlight and I can control it. Without it neither Linux, nor MControlPanel is capable to control the backlight.

[glpnk]

G2_1 is wrong config, right one is G2_5

I'll wipe your code and fix to correct config.

You should use https://openrgb.org/ for your RGB keyboard. I have no idea if your model is supported

[glpnk]

what is MS-1606?

[ItsVaidas]

Yea, I got it from the USB ID that controls the lighting: 0db0:1606
1606 seamed significant, wrote it into the description, AI fixing the description could have written it as MS-1606

[glpnk]

Where you got code for backlight control? If it's yours - you can release it as new project, but it can't be bundled with msi-ec

[glpnk]

Added, thank you

[ItsVaidas]

I checked multiple projects, including the windows version of MSI Control center. After determining where it controls the backlight, wrote the code to change the backlight and with the help of AI to fix any problems it sees in the code (as it's been a long time since I touched c).
I have also made changes to the OpenRGB, but haven't yet opened a pr.

[glpnk]

Okay, good luck with PRing the OpenRGB.

In my opinion keyboard RGB controller which connected via USB shouldn't be a kernel module, but userspace app/service. And OpenRGB seems to be good balance.

For some reason, MSI choose such weird way of control, in comparison to other, where is worth to use kernel modules