[PATCH] platform/x86: redmi-wmi: report EC state change events

[Musaev Ibragim <atomicus.xyz@gmail.com>]

The Redmibook EC/firmware fully handles the keyboard backlight cycle,
the OEM preset power mode (Fn+K) and the Fn lock toggle by itself, and
sends a WMI event carrying the resulting state in the third payload
byte. These events are currently swallowed with KE_IGNORE, so userspace
never learns that the state changed and cannot give the user any
feedback (OSD), even though the WMI event is the only notification
channel for these EC-driven changes.

Report them as key presses instead:

  - keyboard backlight cycle -> KEY_KBDILLUMTOGGLE
  - OEM preset power mode    -> KEY_PERFORMANCE
  - Fn lock toggle           -> KEY_FN_ESC

Desktops that only look at the keycode get the usual hotkey behaviour;
since sparse-keymap emits MSC_SCAN with the raw payload before the key
event, an OSD daemon can additionally recover the exact new state from
byte 2 (e.g. backlight Off/Low/High/Auto is 0x00/0x05/0x0a/0x80).

Note that the power mode event must keep being read from the WMI device
in any case: on the TM2209 the ACPI event handler (EV20) applies the
mode change as a side effect of building the event payload for _WED.

Tested on Redmi Book Pro 15 2023 (TM2209).

Signed-off-by: Musaev Ibragim <atomicus.xyz@gmail.com>
---
A related problem noticed while testing this: bitland-mifs-wmi lists the
same event GUID (46C93E13-EE9B-4262-8488-563BCA757FEF, BITLAND_EVENT_GUID)
in its wmi_device_id table, so on a Redmibook both drivers race for the
event device at boot and whichever probes first wins. When bitland-mifs-wmi
wins, the "Redmibook WMI keys" input device never appears, and since the
MIFS control methods don't work on this machine either (different SMM
interface — platform_profile writes fail, the kbd_backlight LED always
reads 0), the laptop is left with no working Fn events at all until
bitland_mifs_wmi is blacklisted. Should bitland-mifs-wmi gate its binding
on DMI, or is another way to resolve the overlap preferred? Happy to test
patches on TM2209.

 drivers/platform/x86/redmi-wmi.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/platform/x86/redmi-wmi.c b/drivers/platform/x86/redmi-wmi.c
index 5889863..cc82ef5 100644
--- a/drivers/platform/x86/redmi-wmi.c
+++ b/drivers/platform/x86/redmi-wmi.c
@@ -29,24 +29,24 @@ static const struct key_entry redmi_wmi_keymap[] = {
 	{KE_KEY, 0x00011801,	{KEY_ASSISTANT}},
 	{KE_KEY, 0x00011901,	{KEY_ASSISTANT}},
 
-	/* Keyboard backlight */
-	{KE_IGNORE, 0x00000501, {}},
-	{KE_IGNORE, 0x00800501, {}},
-	{KE_IGNORE, 0x00050501, {}},
-	{KE_IGNORE, 0x000a0501, {}},
+	/* Keyboard backlight: Off / Auto / Low / High (new state in byte 2) */
+	{KE_KEY, 0x00000501,	{KEY_KBDILLUMTOGGLE}},
+	{KE_KEY, 0x00800501,	{KEY_KBDILLUMTOGGLE}},
+	{KE_KEY, 0x00050501,	{KEY_KBDILLUMTOGGLE}},
+	{KE_KEY, 0x000a0501,	{KEY_KBDILLUMTOGGLE}},
 
 	/* Xiaomi G Command Center */
 	{KE_KEY, 0x00010a01,	{KEY_VENDOR}},
 
-	/* OEM preset power mode */
-	{KE_IGNORE, 0x00011601, {}},
-	{KE_IGNORE, 0x00021601, {}},
-	{KE_IGNORE, 0x00031601, {}},
-	{KE_IGNORE, 0x00041601, {}},
+	/* OEM preset power mode: 1=Balanced 2=Silent 3=Turbo 4=Full speed */
+	{KE_KEY, 0x00011601,	{KEY_PERFORMANCE}},
+	{KE_KEY, 0x00021601,	{KEY_PERFORMANCE}},
+	{KE_KEY, 0x00031601,	{KEY_PERFORMANCE}},
+	{KE_KEY, 0x00041601,	{KEY_PERFORMANCE}},
 
-	/* Fn Lock state */
-	{KE_IGNORE, 0x00000701, {}},
-	{KE_IGNORE, 0x00010701, {}},
+	/* Fn Lock state: 1=on 0=off */
+	{KE_KEY, 0x00000701,	{KEY_FN_ESC}},
+	{KE_KEY, 0x00010701,	{KEY_FN_ESC}},
 
 	/* Fn+`/1/2/3/4 */
 	{KE_KEY, 0x00011101, {KEY_F13}},
-- 
2.54.0