[PATCH v9 11/12] leds: Add common LED binding parsing support to LED class/core

[Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>]

Quick grep for 'for_each' or 'linux,default-trigger' or
'default-state' under drivers/leds can tell quite a lot. It seems
multiple LED controller drivers implement the very similar looping
through the child nodes in order to locate the LED nodes and read
and support the common LED dt bindings. Implementing this same
stuff for all LED controllers gets old pretty fast.

This commit adds support for locating the LED node (based on known
node names - or given property name-value pair) and handling of
few common LED properties.

linux,default-trigger,
default-state (with the exception of keep),

(in addition to already handled
function-enumerator,
function,
color
and label).

The handling of linux,default-trigger and default-state are omitted
if init_data->parse_fwnode is not set to true. Thus the existing
LED drivers are not impacted until they set this field to true.

Regarding the node look-up:

1. If no init_data is given, then no node-lookup is done and cdev
   name is used as such. (as was earlier)

2. If neither match_property nor of_match is given then passed starting
   point is used as such. (as was earlier - it might help in
   few cases to use dev_fwnode() here but that would change existing
   logic and possibly cause some existing setup to break).

3. If init_data is given but no starting point for node lookup - then
   (parent) device's own DT node is used as starting point for look-up.

4. The match_property has priority over of_match and is first used for
   look-up. If a node with matching property is found then the found node
   is used.

5. If no match_property is given or no mathicng property was found then
   of_macth is used. The node which name matches of_match is searched for
   and used if found.

This ensures that existing drivers which do not populate of_match or
match_property in init_data wont be impacted bu node look-up.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
---
No changes since v8

 drivers/leds/led-class.c | 115 +++++++++++++++--
 drivers/leds/led-core.c  | 258 ++++++++++++++++++++++++++++++++-------
 include/linux/leds.h     |  94 ++++++++++++--
 3 files changed, 401 insertions(+), 66 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 438774315e6c..170ab227eaa9 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -235,6 +235,32 @@ static int led_classdev_next_name(const char *init_name, char *name,
 	return i;
 }
 
+static void led_add_props(struct led_classdev *ld, struct led_properties *props)
+{
+	if (props->default_trigger)
+		ld->default_trigger = props->default_trigger;
+	/*
+	 * According to binding docs the LED is by-default turned OFF unless
+	 * default_state is used to indicate it should be ON or that state
+	 * should be kept as is
+	 */
+	if (props->default_state) {
+		ld->brightness = LED_OFF;
+		if (!strcmp(props->default_state, "on")) {
+			if (!ld->max_brightness)
+				ld->brightness = LED_FULL;
+			else
+				ld->brightness = ld->max_brightness;
+	/*
+	 * We probably should not call the brightness_get prior calling
+	 * the of_parse_cb if one is provided.
+	 * Add a flag to advertice that state should be queried and kept as-is.
+	 */
+		} else if (!strcmp(props->default_state, "keep"))
+			props->brightness_keep = true;
+	}
+}
+
 /**
  * led_classdev_register_ext - register a new object of led_classdev class
  *			       with init data.
@@ -251,22 +277,69 @@ int led_classdev_register_ext(struct device *parent,
 	char final_name[LED_MAX_NAME_SIZE];
 	const char *proposed_name = composed_name;
 	int ret;
-
+	struct led_properties props = {0};
+	struct fwnode_handle *fw;
+
+	/*
+	 * We don't try getting the name based on DT node if init-data is not
+	 * given. We could see if we find LED properties from the device's node
+	 * but that might change LED names for old users of
+	 * led_classdev_register who have been providing the LED name in
+	 * cdev->name. So we seek fwnode for names only if init_data is given
+	 */
 	if (init_data) {
+		led_cdev->init_data = init_data;
 		if (init_data->devname_mandatory && !init_data->devicename) {
 			dev_err(parent, "Mandatory device name is missing");
 			return -EINVAL;
 		}
-		ret = led_compose_name(parent, init_data, composed_name);
+
+		fw = led_get_fwnode(parent, init_data);
+		if (IS_ERR(fw))
+			return PTR_ERR(fw);
+
+		if (fw) {
+			/*
+			 * We did increase refcount for fwnode. Let's set a flag
+			 * so we can decrease it during deregistration
+			 */
+			led_cdev->fwnode_owned = true;
+
+			ret = led_parse_fwnode_props(parent, fw, &props);
+			if (ret)
+				goto err_out;
+
+			if (init_data->of_parse_cb)
+				ret = init_data->of_parse_cb(led_cdev, fw,
+							     &props);
+			if (ret < 0)
+				goto err_out;
+
+			/*
+			 * Handle the common LED properties only for drivers
+			 * that explicitly request it. This allows us to test
+			 * and convert drivers to utilize common LED parsing one
+			 * by one.
+			 */
+			if (init_data->parse_fwnode)
+				led_add_props(led_cdev, &props);
+
+		} else {
+			led_cdev->fwnode_owned = false;
+		}
+		ret = led_compose_name(parent, init_data, &props,
+				       composed_name);
 		if (ret < 0)
-			return ret;
+			goto err_out;
 	} else {
 		proposed_name = led_cdev->name;
+		led_cdev->fwnode_owned = false;
+		fw = NULL;
 	}
 
 	ret = led_classdev_next_name(proposed_name, final_name, sizeof(final_name));
 	if (ret < 0)
-		return ret;
+		goto err_out;
 
 	mutex_init(&led_cdev->led_access);
 	mutex_lock(&led_cdev->led_access);
@@ -274,22 +347,28 @@ int led_classdev_register_ext(struct device *parent,
 				led_cdev, led_cdev->groups, "%s", final_name);
 	if (IS_ERR(led_cdev->dev)) {
 		mutex_unlock(&led_cdev->led_access);
-		return PTR_ERR(led_cdev->dev);
+		ret = PTR_ERR(led_cdev->dev);
+		goto err_out;
 	}
-	if (init_data && init_data->fwnode)
-		led_cdev->dev->fwnode = init_data->fwnode;
+	if (fw)
+		led_cdev->dev->fwnode = fw;
 
 	if (ret)
 		dev_warn(parent, "Led %s renamed to %s due to name collision",
 				led_cdev->name, dev_name(led_cdev->dev));
 
+	if (props.brightness_keep)
+		if (led_cdev->brightness_get)
+			led_cdev->brightness =
+				 led_cdev->brightness_get(led_cdev);
+
 	if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
 		ret = led_add_brightness_hw_changed(led_cdev);
 		if (ret) {
 			device_unregister(led_cdev->dev);
 			led_cdev->dev = NULL;
 			mutex_unlock(&led_cdev->led_access);
-			return ret;
+			goto err_out;
 		}
 	}
 
@@ -322,6 +401,17 @@ int led_classdev_register_ext(struct device *parent,
 			led_cdev->name);
 
 	return 0;
+err_out:
+	if (led_cdev->fwnode_owned) {
+		fwnode_handle_put(fw);
+		/*
+		 * This might not be needed as 'fwnode_owned' is always
+		 * initialized in led_classdev_register_ext
+		 */
+		led_cdev->fwnode_owned = false;
+	}
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(led_classdev_register_ext);
 
@@ -355,6 +445,15 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
 	if (led_cdev->flags & LED_BRIGHT_HW_CHANGED)
 		led_remove_brightness_hw_changed(led_cdev);
 
+	if (led_cdev->fwnode_owned) {
+		fwnode_handle_put(led_cdev->dev->fwnode);
+		/*
+		 * This might not be needed as 'fwnode_owned' is always
+		 * initialized in led_classdev_register_ext
+		 */
+		led_cdev->fwnode_owned = false;
+	}
+
 	device_unregister(led_cdev->dev);
 
 	down_write(&leds_list_lock);
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index f1f718dbe0f8..3cd1784494f2 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -365,70 +365,226 @@ void led_sysfs_enable(struct led_classdev *led_cdev)
 }
 EXPORT_SYMBOL_GPL(led_sysfs_enable);
 
-static void led_parse_fwnode_props(struct device *dev,
-				   struct fwnode_handle *fwnode,
-				   struct led_properties *props)
+static int fw_is_match(struct fwnode_handle *fw,
+		       struct led_fw_match_property *mp, void *val)
 {
-	int ret;
+	void *cmp = mp->raw_val;
+	int ret = -EINVAL;
+
+	if (mp->raw_val) {
+		ret = fwnode_property_read_u8_array(fw, mp->name, val,
+						    mp->size);
+	} else if (mp->intval) {
+		cmp = mp->intval;
+		switch (mp->size) {
+		case 1:
+			ret = fwnode_property_read_u8_array(fw, mp->name, val,
+						    mp->size);
+			break;
+		case 2:
+			ret = fwnode_property_read_u16_array(fw, mp->name, val,
+						    mp->size);
+			break;
+		case 4:
+			ret = fwnode_property_read_u32_array(fw, mp->name, val,
+						    mp->size);
+			break;
+		case 8:
+			ret = fwnode_property_read_u64_array(fw, mp->name, val,
+						    mp->size);
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+	if (!ret && cmp)
+		if (!memcmp(val, cmp, mp->size))
+			return 1;
+
+	return 0;
+}
+/**
+ * led_get_fwnode - find fwnode for led
+ * @parent	LED controller device
+ * @init_data	led init data with match information
+ *
+ * Scans the firmware nodes and returns node matching the given init_data.
+ * NOTE: Function increases refcount for found node. Caller must decrease
+ * refcount using fwnode_handle_put when finished with node.
+ */
+struct fwnode_handle *led_get_fwnode(struct device *parent,
+				      struct led_init_data *init_data)
+{
+	struct fwnode_handle *fw;
+
+	/*
+	 * This should never be called without init data. We could always return
+	 * dev_fwnode() - but then we should pump-up the refcount
+	 */
+	if (!init_data)
+		return NULL;
+
+	/*
+	 * For now we do only do node look-up for drivers which populate
+	 * the new match properties. We could and perhaps should do
+	 * fw = dev_fwnode(parent); if given fwnode is NULL. But in order not to
+	 * break the existing setups we keep the old behaviour and just directly
+	 * use the given init_data->fwnode no matter if it is NULL or not.
+	 */
+
+	if ((!init_data->match_property.name ||
+	     !init_data->match_property.size) && !init_data->of_match)
+		return fwnode_handle_get(init_data->fwnode);
+
+	/* match information was given - do node look-up */
+
+	if (!init_data->fwnode)
+		fw = dev_fwnode(parent);
+	else
+		fw = init_data->fwnode;
+
+	if (!fw)
+		return NULL;
+
+	/*
+	 * Simple things are pretty. I think simplest is to use DT node-name
+	 * for matching the node with LED - same way regulators use the node
+	 * name to match with desc.
+	 *
+	 * This may not work with existing LED DT entries if the node name has
+	 * been freely pickable. In order to this to work the binding doc
+	 * for LED driver should define usable node names.
+	 *
+	 * If this is not working we can define specific match property which
+	 * value we scan and use for matching for LEDs connected to the
+	 * controller.
+	 */
+	if (init_data->match_property.name && init_data->match_property.size) {
+		u8 *val;
+		int ret;
+		struct fwnode_handle *child;
+		struct led_fw_match_property *mp;
+
+		mp = &init_data->match_property;
+
+		val = kzalloc(mp->size, GFP_KERNEL);
+		if (!val)
+			return ERR_PTR(-ENOMEM);
+
+		fwnode_for_each_child_node(fw, child) {
+			ret = fw_is_match(child, mp, val);
+			if (ret > 0) {
+				kfree(val);
+				return child;
+			}
+			if (ret < 0) {
+				dev_err(parent,
+					"invalid fw match. Use raw_val?\n");
+				fwnode_handle_put(child);
+				break;
+			}
+		}
+		kfree(val);
+	}
+	if (init_data->of_match)
+		fw = fwnode_get_named_child_node(fw, init_data->of_match);
+
+	return fw;
+}
+EXPORT_SYMBOL(led_get_fwnode);
+
+int led_parse_fwnode_props(struct device *dev, struct fwnode_handle *fwnode,
+			   struct led_properties *props)
+{
+	int ret = 0;
 
 	if (!fwnode)
-		return;
+		return 0;
 
 	if (fwnode_property_present(fwnode, "label")) {
 		ret = fwnode_property_read_string(fwnode, "label", &props->label);
 		if (ret)
 			dev_err(dev, "Error parsing 'label' property (%d)\n", ret);
-		return;
+		return ret;
 	}
 
+	/*
+	 * Please note, logic changed - if invalid property is found we bail
+	 * early out without parsing the rest of the properties. Originally
+	 * this was the case only for 'label' property. I don't know the
+	 * rationale behind original logic allowing invalid properties to be
+	 * given. If there is a reason then we should reconsider this.
+	 * Intuitively it feels correct to just yell and quit if we hit value we
+	 * don't understand - but intuition may be wrong at times :)
+	 */
 	if (fwnode_property_present(fwnode, "color")) {
 		ret = fwnode_property_read_u32(fwnode, "color", &props->color);
-		if (ret)
+		if (ret) {
 			dev_err(dev, "Error parsing 'color' property (%d)\n", ret);
-		else if (props->color >= LED_COLOR_ID_MAX)
+			return ret;
+		} else if (props->color >= LED_COLOR_ID_MAX) {
 			dev_err(dev, "LED color identifier out of range\n");
-		else
-			props->color_present = true;
+			return ret;
+		}
+		props->color_present = true;
 	}
 
+	if (fwnode_property_present(fwnode, "function")) {
+		ret = fwnode_property_read_string(fwnode, "function",
+						  &props->function);
+		if (ret) {
+			dev_err(dev,
+				"Error parsing 'function' property (%d)\n",
+				ret);
+			return ret;
+		}
+	}
 
-	if (!fwnode_property_present(fwnode, "function"))
-		return;
-
-	ret = fwnode_property_read_string(fwnode, "function", &props->function);
-	if (ret) {
-		dev_err(dev,
-			"Error parsing 'function' property (%d)\n",
-			ret);
+	if (fwnode_property_present(fwnode, "function-enumerator")) {
+		ret = fwnode_property_read_u32(fwnode, "function-enumerator",
+					       &props->func_enum);
+		if (ret) {
+			dev_err(dev,
+				"Error parsing 'function-enumerator' property (%d)\n",
+				ret);
+			return ret;
+		}
+		props->func_enum_present = true;
 	}
 
-	if (!fwnode_property_present(fwnode, "function-enumerator"))
-		return;
+	if (fwnode_property_present(fwnode, "default-state")) {
+		ret = fwnode_property_read_string(fwnode, "default-state",
+						  &props->default_state);
+		if (ret) {
+			dev_err(dev,
+				"Error parsing 'default-state' property (%d)\n",
+				ret);
+			return ret;
+		}
+	}
 
-	ret = fwnode_property_read_u32(fwnode, "function-enumerator",
-				       &props->func_enum);
-	if (ret) {
-		dev_err(dev,
-			"Error parsing 'function-enumerator' property (%d)\n",
-			ret);
-	} else {
-		props->func_enum_present = true;
+	if (fwnode_property_present(fwnode, "linux,default-trigger")) {
+		ret = fwnode_property_read_string(fwnode,
+						  "linux,default-trigger",
+						  &props->default_trigger);
+		if (ret)
+			dev_err(dev,
+				"Error parsing 'linux,default-trigger' property (%d)\n",
+				ret);
 	}
+	return ret;
 }
+EXPORT_SYMBOL_GPL(led_parse_fwnode_props);
 
 int led_compose_name(struct device *dev, struct led_init_data *init_data,
-		     char *led_classdev_name)
+		     struct led_properties *props, char *led_classdev_name)
 {
-	struct led_properties props = {};
-	struct fwnode_handle *fwnode = init_data->fwnode;
 	const char *devicename = init_data->devicename;
 
 	if (!led_classdev_name)
 		return -EINVAL;
 
-	led_parse_fwnode_props(dev, fwnode, &props);
-
-	if (props.label) {
+	if (props->label) {
 		/*
 		 * If init_data.devicename is NULL, then it indicates that
 		 * DT label should be used as-is for LED class device name.
@@ -436,23 +592,23 @@ int led_compose_name(struct device *dev, struct led_init_data *init_data,
 		 * the final LED class device name.
 		 */
 		if (!devicename) {
-			strscpy(led_classdev_name, props.label,
+			strscpy(led_classdev_name, props->label,
 				LED_MAX_NAME_SIZE);
 		} else {
 			snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
-				 devicename, props.label);
+				 devicename, props->label);
 		}
-	} else if (props.function || props.color_present) {
+	} else if (props->function || props->color_present) {
 		char tmp_buf[LED_MAX_NAME_SIZE];
 
-		if (props.func_enum_present) {
+		if (props->func_enum_present) {
 			snprintf(tmp_buf, LED_MAX_NAME_SIZE, "%s:%s-%d",
-				 props.color_present ? led_colors[props.color] : "",
-				 props.function ?: "", props.func_enum);
+				 props->color_present ? led_colors[props->color] : "",
+				 props->function ?: "", props->func_enum);
 		} else {
 			snprintf(tmp_buf, LED_MAX_NAME_SIZE, "%s:%s",
-				 props.color_present ? led_colors[props.color] : "",
-				 props.function ?: "");
+				 props->color_present ? led_colors[props->color] : "",
+				 props->function ?: "");
 		}
 		if (init_data->devname_mandatory) {
 			snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
@@ -468,11 +624,19 @@ int led_compose_name(struct device *dev, struct led_init_data *init_data,
 		}
 		snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
 			 devicename, init_data->default_label);
-	} else if (is_of_node(fwnode)) {
-		strscpy(led_classdev_name, to_of_node(fwnode)->name,
-			LED_MAX_NAME_SIZE);
-	} else
-		return -EINVAL;
+	} else {
+		struct fwnode_handle *fwnode = led_get_fwnode(dev, init_data);
+		int ret = -EINVAL;
+
+		if (is_of_node(fwnode)) {
+			ret = 0;
+			strscpy(led_classdev_name, to_of_node(fwnode)->name,
+				LED_MAX_NAME_SIZE);
+		}
+		fwnode_handle_put(fwnode);
+
+		return ret;
+	}
 
 	return 0;
 }
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 242258f7d837..af8ca4291d7d 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -13,6 +13,7 @@
 #include <linux/kernfs.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
+#include <linux/property.h>
 #include <linux/rwsem.h>
 #include <linux/spinlock.h>
 #include <linux/timer.h>
@@ -20,6 +21,7 @@
 
 struct device;
 struct led_pattern;
+struct led_classdev;
 /*
  * LED Core
  */
@@ -31,8 +33,47 @@ enum led_brightness {
 	LED_FULL	= 255,
 };
 
+struct led_properties {
+	u32		color;
+	bool		color_present;
+	const char	*function;
+	u32		func_enum;
+	bool		func_enum_present;
+	const char	*label;
+	const char	*default_trigger;
+	const char	*default_state;
+	bool		brightness_keep;
+};
+
+struct led_fw_match_property {
+	const char *name;	/* Name of the property to match */
+	void *raw_val;		/* Raw property value as present in fwnode */
+	void *intval;		/* Property value if 8,16,32 or 64bit integer */
+	size_t size;		/* Size of value in bytes */
+};
+
 struct led_init_data {
-	/* device fwnode handle */
+	/*
+	 * If DT binding dictates the node name the driver can fill of_match
+	 * corresponding to node name describing this LED. If fwnode is given
+	 * the match is searched from it's child nodes. If not, the match is
+	 * searched from device's own child nodes.
+	 */
+	const char *of_match;
+	/*
+	 * If fwnode contains property with known value the driver can specify
+	 * correct propertty-value pair here to do the matching. This has higher
+	 * priority than of_match. If fwnode is given the match is searched
+	 * from it's child nodes. If not match is searched from device's
+	 * own child nodes.
+	 */
+	struct led_fw_match_property match_property;
+	/*
+	 * device fwnode handle. If of_match or led_compatible are not given
+	 * this is used for LED as given. If of_match or led_compatible are
+	 * given then this is used as a parent node whose child nodes are
+	 * scanned for given match.
+	 */
 	struct fwnode_handle *fwnode;
 	/*
 	 * default <color:function> tuple, for backward compatibility
@@ -53,9 +94,19 @@ struct led_init_data {
 	 * set it to true
 	 */
 	bool devname_mandatory;
+	/*
+	 * Callback which a LED driver can register if it has own non-standard
+	 * DT properties. Core calls this with the located DT node during
+	 * class_device registration
+	 */
+	int (*of_parse_cb)(struct led_classdev *ld, struct fwnode_handle *fw,
+			    struct led_properties *props);
+	 /* LED core should parse and handle the common firmware properties */
+	bool parse_fwnode;
 };
 
 struct led_classdev {
+	struct led_init_data	*init_data;
 	const char		*name;
 	enum led_brightness	 brightness;
 	enum led_brightness	 max_brightness;
@@ -148,6 +199,7 @@ struct led_classdev {
 
 	/* Ensures consistent access to the LED Flash Class device */
 	struct mutex		led_access;
+	bool			fwnode_owned;
 };
 
 /**
@@ -299,6 +351,7 @@ void led_sysfs_enable(struct led_classdev *led_cdev);
  * led_compose_name - compose LED class device name
  * @dev: LED controller device object
  * @init_data: the LED class device initialization data
+ * @props: LED properties as parsed from fwnode.
  * @led_classdev_name: composed LED class device name
  *
  * Create LED class device name basing on the provided init_data argument.
@@ -308,7 +361,8 @@ void led_sysfs_enable(struct led_classdev *led_cdev);
  * Returns: 0 on success or negative error value on failure
  */
 int led_compose_name(struct device *dev, struct led_init_data *init_data,
-		     char *led_classdev_name);
+			    struct led_properties *props,
+			    char *led_classdev_name);
 
 /**
  * led_sysfs_is_disabled - check if LED sysfs interface is disabled
@@ -321,6 +375,33 @@ static inline bool led_sysfs_is_disabled(struct led_classdev *led_cdev)
 	return led_cdev->flags & LED_SYSFS_DISABLE;
 }
 
+/**
+ * led_get_fwnode - find fwnode matching given LED init data
+ * @parent: LED controller device this LED is driven by
+ * @init_data: the LED class device initialization data
+ *
+ * Find the fw node matching given LED init data.
+ * NOTE: Function increases refcount for found node. Caller must decrease
+ * refcount using fwnode_handle_put when finished with node.
+ *
+ * Returns: node handle or NULL if matching fw node was not found
+ */
+struct fwnode_handle *led_get_fwnode(struct device *parent,
+				      struct led_init_data *init_data);
+
+/**
+ * led_parse_fwnode_props - parse LED common properties from fwnode
+ * @dev: pointer to LED device.
+ * @fwnode: LED node containing the properties
+ * @props: structure where found property data is stored.
+ *
+ * Parse the common LED properties from fwnode.
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+int led_parse_fwnode_props(struct device *dev, struct fwnode_handle *fwnode,
+			   struct led_properties *props);
+
 /*
  * LED Triggers
  */
@@ -478,15 +559,6 @@ struct led_platform_data {
 	struct led_info	*leds;
 };
 
-struct led_properties {
-	u32		color;
-	bool		color_present;
-	const char	*function;
-	u32		func_enum;
-	bool		func_enum_present;
-	const char	*label;
-};
-
 struct gpio_desc;
 typedef int (*gpio_blink_set_t)(struct gpio_desc *desc, int state,
 				unsigned long *delay_on,
-- 
2.21.0


-- 
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =]