> Date: Sun, 13 Oct 2019 21:37:53 -0500
> From: joshua stein <[email protected]>
>
> Newer ThinkPads have ACPI goo to allow acpivout to control screen
> backlight, so don't take over ws_[gs]et_param from it. This allows
> for 100 levels of backlight control rather than the 10 or 15 that
> are supported through acpithinkpad using its proprietary ACPI or
> CMOS interfaces.
>
> You can see the difference with and without this patch by doing:
>
> xbacklight -set 1 -steps 100
> xbacklight -set 100 -steps 100
>
> Apparently this will also be needed for newer AMD ThinkPads that use
> radeondrm.
>
> "Newer" here is being defined as anything not reporting version 1
> (THINKPAD_HKEY_VERSION1) of the ThinkPad ACPI interface.
Note that -current reports the version number in dmesg. For now
you'll need to compile your own kernel though, since there won't be
any new snapshots until 6.6 is released.
> For responding to hardware brightness keys, you'll want to test with
> the acpivout patch I posted since otherwise the keys will be
> adjusting the backlight by 1% each time, and it may seem like it's
> not doing anything. That patch makes it properly adjust by 5% each
> time (but you still get fine-grained changes through wsconsctl or
> xbacklight).
Wo what we need to get tested is whether backlight control (stil)
works on machines that report:
acpithinkpad0 at acpi0: version 2.0
My x1c3 reports version 1.0 so I suspect the x250/t450/t550 reports
that as well (but it would be goo to get that confirmed). So we're
primarily interested in later generations.
> Index: sys/dev/acpi/acpithinkpad.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/acpi/acpithinkpad.c,v
> retrieving revision 1.66
> diff -u -p -u -p -r1.66 acpithinkpad.c
> --- sys/dev/acpi/acpithinkpad.c 13 Oct 2019 10:56:31 -0000 1.66
> +++ sys/dev/acpi/acpithinkpad.c 14 Oct 2019 02:28:57 -0000
> @@ -320,8 +320,10 @@ thinkpad_attach(struct device *parent, s
> wskbd_set_backlight = thinkpad_set_kbd_backlight;
> }
>
> - if (aml_evalinteger(sc->sc_acpi, sc->sc_devnode, "PBLG",
> - 0, NULL, &sc->sc_brightness) == 0) {
> + /* On version 2 and newer, let *drm or acpivout control brightness */
> + if (sc->sc_hkey_version == THINKPAD_HKEY_VERSION1 &&
> + (aml_evalinteger(sc->sc_acpi, sc->sc_devnode, "PBLG",
> + 0, NULL, &sc->sc_brightness) == 0)) {
> ws_get_param = thinkpad_get_param;
> ws_set_param = thinkpad_set_param;
> }
>
>
