[PATCH v3 4/7] platform/x86: thinkpad_acpi: Detect auto-mode capability via MLCG

[Qiling Zhu <kmatzkaczor244@gmail.com>]

The upper bits of the MLCG return value carry capability information.
Bit 20 indicates whether the EC supports the auto mode of the keyboard
backlight (0 = manual levels only, 1 = auto mode available), as defined
by the firmware.

Record it in tp_features.kbdlight_auto, in preparation for using it to
gate the auto-mode trigger registration and the LED suspend/resume
skipping in subsequent changes.

Link: https://lore.kernel.org/r/CABxCQKuEP5wMSstO0MK1MhaqXTKrPhUSN3V2mrE_42j4cXsXZQ@mail.gmail.com
Signed-off-by: Qiling Zhu <kmatzkaczor244@gmail.com>
---
 drivers/platform/x86/lenovo/thinkpad_acpi.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
index 657a19d11..681b340a1 100644
--- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
+++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
@@ -363,6 +363,7 @@ static struct {
 		TP_HOTKEY_TABLET_USES_GMMS,
 	} hotkey_tablet;
 	u32 kbdlight:1;
+	u32 kbdlight_auto:1;
 	u32 light:1;
 	u32 light_status:1;
 	u32 bright_acpimode:1;
@@ -5161,6 +5162,13 @@ static bool kbdlight_is_supported(void)
 	}
 
 	vdbg_printk(TPACPI_DBG_INIT, "kbdlight MLCG returned 0x%x\n", status);
+
+	/*
+	 * MLCG bit 20 indicates auto mode support: 0 = manual levels only,
+	 * 1 = auto mode available (per the firmware definition).
+	 */
+	tp_features.kbdlight_auto = !!(status & BIT(20));
+
 	/*
 	 * Guessed test for keyboard backlight:
 	 *
-- 
2.56.1