[PATCH v2] thinkpad_acpi: Add support for X1 Yoga (2016) Tablet Mode

[Lyude <lyude@redhat.com>]

For whatever reason, the X1 Yoga doesn't support the normal method of
querying for tablet mode. Instead of providing the MHKG method under the
hotkey handle, we're instead given the CMMD method under the EC handle.
Values on this handle are either 0x1, laptop mode, or 0x6, tablet mode.

Changes since v1:
- Clarify kernel output when finding the tablet mode switch

Signed-off-by: Lyude <lyude@redhat.com>
---
 drivers/platform/x86/thinkpad_acpi.c | 36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index b65ce75..d9f9956 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -190,6 +190,9 @@ enum tpacpi_hkey_event_t {
 	TP_HKEY_EV_LID_OPEN		= 0x5002, /* laptop lid opened */
 	TP_HKEY_EV_TABLET_TABLET	= 0x5009, /* tablet swivel up */
 	TP_HKEY_EV_TABLET_NOTEBOOK	= 0x500a, /* tablet swivel down */
+	TP_HKEY_EV_TABLET_CHANGED	= 0x60c0, /* X1 Yoga (2016):
+						   * enter/leave tablet mode
+						   */
 	TP_HKEY_EV_PEN_INSERTED		= 0x500b, /* tablet pen inserted */
 	TP_HKEY_EV_PEN_REMOVED		= 0x500c, /* tablet pen removed */
 	TP_HKEY_EV_BRGHT_CHANGED	= 0x5010, /* backlight control event */
@@ -303,6 +306,7 @@ static struct {
 	u32 hotkey_mask:1;
 	u32 hotkey_wlsw:1;
 	u32 hotkey_tablet:1;
+	u32 hotkey_tablet_cmmd:1;
 	u32 kbdlight:1;
 	u32 light:1;
 	u32 light_status:1;
@@ -2059,6 +2063,8 @@ static void hotkey_poll_setup(const bool may_warn);
 
 /* HKEY.MHKG() return bits */
 #define TP_HOTKEY_TABLET_MASK (1 << 3)
+/* ThinkPad X1 Yoga (2016) */
+#define TP_EC_CMMD_TABLET_MODE 0x6
 
 static int hotkey_get_wlsw(void)
 {
@@ -2083,10 +2089,18 @@ static int hotkey_get_tablet_mode(int *status)
 {
 	int s;
 
-	if (!acpi_evalf(hkey_handle, &s, "MHKG", "d"))
-		return -EIO;
+	if (tp_features.hotkey_tablet_cmmd) {
+		if (!acpi_evalf(ec_handle, &s, "CMMD", "d"))
+			return -EIO;
+
+		*status = (s == TP_EC_CMMD_TABLET_MODE);
+	} else {
+		if (!acpi_evalf(hkey_handle, &s, "MHKG", "d"))
+			return -EIO;
+
+		*status = ((s & TP_HOTKEY_TABLET_MASK) != 0);
+	}
 
-	*status = ((s & TP_HOTKEY_TABLET_MASK) != 0);
 	return 0;
 }
 
@@ -3475,6 +3489,18 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 				&dev_attr_hotkey_tablet_mode.attr);
 	}
 
+	/* For X1 Yoga (2016) */
+	if (!res && acpi_evalf(ec_handle, &status, "CMMD", "qd")) {
+		tp_features.hotkey_tablet = 1;
+		tp_features.hotkey_tablet_cmmd = 1;
+		tabletsw_state = (status == TP_EC_CMMD_TABLET_MODE);
+
+		pr_info("Tablet mode switch found (X1 Yoga style); ThinkPad in %s mode\n",
+			(tabletsw_state) ? "tablet" : "laptop");
+		res = add_to_attr_set(hotkey_dev_attributes,
+				      &dev_attr_hotkey_tablet_mode.attr);
+	}
+
 	if (!res)
 		res = register_attr_set_with_sysfs(
 				hotkey_dev_attributes,
@@ -3899,6 +3925,10 @@ static bool hotkey_notify_6xxx(const u32 hkey,
 		*ignore_acpi_ev = true;
 		return true;
 
+	case TP_HKEY_EV_TABLET_CHANGED:
+		tpacpi_input_send_tabletsw();
+		break;
+
 	default:
 		pr_warn("unknown possible thermal alarm or keyboard event received\n");
 		known = false;
-- 
2.7.4