ACPI: thinkpad-acpi: add tablet-mode reporting

A quick study of the 0x5009/0x500A HKEY event on the X61t DSDT revealed the
existence of the EC HTAB register (EC 0x0f, bit 7), and a compare with the
X41t DSDT shows that HKEY.MHKG can be used to verify if the ThinkPad is
tablet-capable (MHKG present), and in tablet mode (bit 3 of MHKG return is
set).

Add an attribute to report this information, "hotkey_tablet_mode".  This
attribute has poll()/select() support, and can be used along with EV_SW
SW_TABLET_MODE to hook userspace to tablet events.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

Documentation/laptops/thinkpad-acpi.txt

@@ -313,6 +313,13 @@ sysfs notes:
 
 		This attribute has poll()/select() support.
 
+	hotkey_tablet_mode:
+		If the ThinkPad has tablet capabilities, this attribute
+		will read 0 if the ThinkPad is in normal mode, and
+		1 if the ThinkPad is in tablet mode.
+
+		This attribute has poll()/select() support.
+
 	hotkey_report_mode:
 		Returns the state of the procfs ACPI event report mode
 		filter for hot keys.  If it is set to 1 (the default),

drivers/misc/thinkpad_acpi.c

@@ -221,6 +221,7 @@ static struct {
 	u32 hotkey:1;
 	u32 hotkey_mask:1;
 	u32 hotkey_wlsw:1;
+	u32 hotkey_tablet:1;
 	u32 light:1;
 	u32 light_status:1;
 	u32 bright_16levels:1;
@@ -1060,13 +1061,26 @@ static struct attribute_set *hotkey_dev_attributes;
 #define HOTKEY_CONFIG_CRITICAL_END
 #endif /* CONFIG_THINKPAD_ACPI_HOTKEY_POLL */
 
+/* HKEY.MHKG() return bits */
+#define TP_HOTKEY_TABLET_MASK (1 << 3)
+
 static int hotkey_get_wlsw(int *status)
 {
 	if (!acpi_evalf(hkey_handle, status, "WLSW", "d"))
 		return -EIO;
 	return 0;
 }
 
+static int hotkey_get_tablet_mode(int *status)
+{
+	int s;
+
+	if (!acpi_evalf(hkey_handle, &s, "MHKG", "d"))
+		return -EIO;
+
+	return ((s & TP_HOTKEY_TABLET_MASK) != 0);
+}
+
 /*
  * Call with hotkey_mutex held
  */
@@ -1172,15 +1186,20 @@ static void tpacpi_input_send_radiosw(void)
 	}
 }
 
-static void tpacpi_input_send_tabletsw(unsigned int state)
+static void tpacpi_input_send_tabletsw(void)
 {
-	mutex_lock(&tpacpi_inputdev_send_mutex);
+	int state;
 
-	input_report_switch(tpacpi_inputdev,
-			    SW_TABLET_MODE, !!state);
-	input_sync(tpacpi_inputdev);
+	if (tp_features.hotkey_tablet &&
+	    !hotkey_get_tablet_mode(&state)) {
+		mutex_lock(&tpacpi_inputdev_send_mutex);
 
-	mutex_unlock(&tpacpi_inputdev_send_mutex);
+		input_report_switch(tpacpi_inputdev,
+				    SW_TABLET_MODE, !!state);
+		input_sync(tpacpi_inputdev);
+
+		mutex_unlock(&tpacpi_inputdev_send_mutex);
+	}
 }
 
 static void tpacpi_input_send_key(unsigned int scancode)
@@ -1691,6 +1710,29 @@ static void hotkey_radio_sw_notify_change(void)
 			     "hotkey_radio_sw");
 }
 
+/* sysfs hotkey tablet mode (pollable) --------------------------------- */
+static ssize_t hotkey_tablet_mode_show(struct device *dev,
+			   struct device_attribute *attr,
+			   char *buf)
+{
+	int res, s;
+	res = hotkey_get_tablet_mode(&s);
+	if (res < 0)
+		return res;
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", !!s);
+}
+
+static struct device_attribute dev_attr_hotkey_tablet_mode =
+	__ATTR(hotkey_tablet_mode, S_IRUGO, hotkey_tablet_mode_show, NULL);
+
+static void hotkey_tablet_mode_notify_change(void)
+{
+	if (tp_features.hotkey_tablet)
+		sysfs_notify(&tpacpi_pdev->dev.kobj, NULL,
+			     "hotkey_tablet_mode");
+}
+
 /* sysfs hotkey report_mode -------------------------------------------- */
 static ssize_t hotkey_report_mode_show(struct device *dev,
 			   struct device_attribute *attr,
@@ -1903,7 +1945,7 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 		str_supported(tp_features.hotkey));
 
 	if (tp_features.hotkey) {
-		hotkey_dev_attributes = create_attr_set(12, NULL);
+		hotkey_dev_attributes = create_attr_set(13, NULL);
 		if (!hotkey_dev_attributes)
 			return -ENOMEM;
 		res = add_many_to_attr_set(hotkey_dev_attributes,
@@ -1982,6 +2024,18 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 					&dev_attr_hotkey_radio_sw.attr);
 		}
 
+		/* For X41t, X60t, X61t Tablets... */
+		if (!res && acpi_evalf(hkey_handle, &status, "MHKG", "qd")) {
+			tp_features.hotkey_tablet = 1;
+			printk(TPACPI_INFO
+				"possible tablet mode switch found; "
+				"ThinkPad in %s mode\n",
+				(status & TP_HOTKEY_TABLET_MASK)?
+					"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,
@@ -2031,7 +2085,7 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 			set_bit(EV_SW, tpacpi_inputdev->evbit);
 			set_bit(SW_RADIO, tpacpi_inputdev->swbit);
 		}
-		if (thinkpad_id.vendor == PCI_VENDOR_ID_LENOVO) {
+		if (tp_features.hotkey_tablet) {
 			set_bit(EV_SW, tpacpi_inputdev->evbit);
 			set_bit(SW_TABLET_MODE, tpacpi_inputdev->swbit);
 		}
@@ -2057,6 +2111,7 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 
 		hotkey_poll_setup_safe(1);
 		tpacpi_input_send_radiosw();
+		tpacpi_input_send_tabletsw();
 	}
 
 	return (tp_features.hotkey)? 0 : 1;
@@ -2187,9 +2242,10 @@ static void hotkey_notify(struct ibm_struct *ibm, u32 event)
 			case 0x500b: /* X61t: tablet pen inserted into bay */
 			case 0x500c: /* X61t: tablet pen removed from bay */
 				break;
-			case 0x5009: /* X61t: swivel up (tablet mode) */
-			case 0x500a: /* X61t: swivel down (normal mode) */
-				tpacpi_input_send_tabletsw((hkey == 0x5009));
+			case 0x5009: /* X41t-X61t: swivel up (tablet mode) */
+			case 0x500a: /* X41t-X61t: swivel down (normal mode) */
+				tpacpi_input_send_tabletsw();
+				hotkey_tablet_mode_notify_change();
 				send_acpi_ev = 0;
 				break;
 			case 0x5001:
@@ -2250,6 +2306,7 @@ static void hotkey_resume(void)
 		       "from firmware\n");
 	tpacpi_input_send_radiosw();
 	hotkey_radio_sw_notify_change();
+	hotkey_tablet_mode_notify_change();
 	hotkey_wakeup_reason_notify_change();
 	hotkey_wakeup_hotunplug_complete_notify_change();
 	hotkey_poll_setup_safe(0);