[PATCH 1/2] input: atkbd: add softleds quirk for broken EC PS/2 emulation

[Rodnei Cilto]

Some Lenovo IdeaPad laptops (e.g. 83RR/83SR, Wildcat Lake) implement
PS/2 keyboard emulation via the Embedded Controller (EC) but do not
fully support the AT protocol. Specifically, sending the SETLEDS
command (0xED) after initialization causes the EC to return corrupted
scancodes (reported as '**' in i8042.debug), rendering the keyboard
non-functional.

The existing SERIO_QUIRK_DUMBKBD resolves scancode corruption by
zeroing serio->write, preventing AT commands. However, LED registration
in atkbd_set_device_attrs() depends on atkbd->write being set, so
dumbkbd mode loses EV_LED capabilities entirely.

Note: serio->id.extra is __u8 (8 bits only) and cannot be used to
pass new quirk flags from i8042 to atkbd. The quirk is detected
directly in atkbd via its DMI quirk table.

Introduce atkbd_softleds: a DMI-detected mode that combines dumbkbd
behaviour (serio->write = NULL, no 0xED sent) with EV_LED registration
so that CapsLock/NumLock/ScrollLock state remains visible to userspace
via the input subsystem.

Add DMI entries for Lenovo IdeaPad 83RR (Wildcat Lake) and its Brazil
regional variant 83SR.

Signed-off-by: Rodnei Cilto <rodnei.cilto@xxxxxxxxx>
---
 drivers/input/keyboard/atkbd.c        | 46 ++++++++++++++++++++++++++++++++++-
 drivers/input/serio/i8042-acpipnpio.h |  3 +++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/input/keyboard/atkbd.c b/drivers/input/keyboard/atkbd.c
index 8cb4dc6fb165..826a21dc016a 100644
--- a/drivers/input/keyboard/atkbd.c
+++ b/drivers/input/keyboard/atkbd.c
@@ -212,6 +212,7 @@ struct atkbd {
 	bool softrepeat;
 	bool softraw;
 	bool scroll;
+	bool softleds;		/* suppress 0xED, register EV_LED in software */
 	bool enabled;
 
 	/* Accessed only from interrupt */
@@ -245,6 +246,7 @@ static unsigned int (*atkbd_platform_scancode_fixup)(struct atkbd *, unsigned in
  * to many commands until full reset (ATKBD_CMD_RESET_BAT) is performed.
  */
 static bool atkbd_skip_deactivate;
+static bool atkbd_softleds;
 
 static ssize_t atkbd_attr_show_helper(struct device *dev, char *buf,
 				      ssize_t (*handler)(struct atkbd *, char *));
@@ -600,6 +602,14 @@ static int atkbd_set_leds(struct atkbd *atkbd)
 	struct input_dev *dev = atkbd->dev;
 	u8 param[2];
 
+	/*
+	 * softleds: EC PS/2 emulation does not support AT commands
+	 * after initialization. Accept LED state from userspace but
+	 * never send SETLEDS (0xED) to avoid scancode corruption.
+	 */
+	if (atkbd->softleds)
+		return 0;
+
 	param[0] = (test_bit(LED_SCROLLL, dev->led) ? 1 : 0)
 		 | (test_bit(LED_NUML,    dev->led) ? 2 : 0)
 		 | (test_bit(LED_CAPSL,   dev->led) ? 4 : 0);
@@ -1193,7 +1203,7 @@ static void atkbd_set_device_attrs(struct atkbd *atkbd)
 	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP) |
 		BIT_MASK(EV_MSC);
 
-	if (atkbd->write) {
+	if (atkbd->write || atkbd->softleds) {
 		input_dev->evbit[0] |= BIT_MASK(EV_LED);
 		input_dev->ledbit[0] = BIT_MASK(LED_NUML) |
 			BIT_MASK(LED_CAPSL) | BIT_MASK(LED_SCROLLL);
@@ -1291,6 +1301,12 @@ static int atkbd_connect(struct serio *serio, struct serio_driver *drv)
 	if (atkbd->softrepeat)
 		atkbd->softraw = true;
 
+	if (atkbd_softleds) {
+		serio->write = NULL;
+		atkbd->write = false;
+		atkbd->softleds = true;
+	}
+
 	serio_set_drvdata(serio, atkbd);
 
 	err = serio_open(serio, drv);
@@ -1767,6 +1783,12 @@ static int __init atkbd_deactivate_fixup(const struct dmi_system_id *id)
 	return 1;
 }
 
+static int __init atkbd_setup_softleds(const struct dmi_system_id *id)
+{
+	atkbd_softleds = true;
+	return 1;
+}
+
 /*
  * NOTE: do not add any more "force release" quirks to this table.  The
  * task of adjusting list of keys that should be "released" automatically
@@ -1938,6 +1960,28 @@ static const struct dmi_system_id atkbd_dmi_quirk_table[] __initconst = {
 		},
 		.callback = atkbd_deactivate_fixup,
 	},
+	{
+		/*
+		 * Lenovo IdeaPad 83RR (Wildcat Lake) - EC PS/2 emulation
+		 * returns corrupted scancodes ('**' in i8042.debug) when
+		 * receiving AT SETLEDS (0xED) after keyboard initialization.
+		 * Enable softleds mode: suppress 0xED to hardware while
+		 * keeping CapsLock/NumLock/ScrollLock visible to userspace.
+		 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "83RR"),
+		},
+		.callback = atkbd_setup_softleds,
+	},
+	{
+		/* Lenovo IdeaPad 83SR (83RR Brazil regional variant) */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "83SR"),
+		},
+		.callback = atkbd_setup_softleds,
+	},
 	{ }
 };
 
diff --git a/drivers/input/serio/i8042-acpipnpio.h b/drivers/input/serio/i8042-acpipnpio.h
index 8ebdf4fb9030..d233544ebac9 100644
--- a/drivers/input/serio/i8042-acpipnpio.h
+++ b/drivers/input/serio/i8042-acpipnpio.h
@@ -79,6 +79,9 @@ static inline void i8042_write_command(int val)
 #define SERIO_QUIRK_DIRECT		BIT(8)
 #define SERIO_QUIRK_DUMBKBD		BIT(9)
 #define SERIO_QUIRK_NOLOOP		BIT(10)
+/* SERIO_QUIRK_DUMBKBD_LEDS handled via atkbd DMI quirk table.
+ * serio->id.extra is __u8 (8 bits only), cannot carry this flag.
+ */
 #define SERIO_QUIRK_NOTIMEOUT		BIT(11)
 #define SERIO_QUIRK_KBDRESET		BIT(12)
 #define SERIO_QUIRK_DRITEK		BIT(13)

-- 
2.51.0