Date:	Thu, 06 Aug 2009 16:31:38 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	linux-acpi <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Pavel Machek <pavel@....cz>, Greg KH <greg@...ah.com>,
	Len Brown <lenb@...nel.org>,
	Richard Purdie <rpurdie@...ys.net>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	"Valdis.Kletnieks@...edu" <Valdis.Kletnieks@...edu>,
	"Zhang, Rui" <rui.zhang@...el.com>
Subject: [RFC PATCH V2 1/2] introduce ALS sysfs class


Introduce ALS sysfs class device.

ALS sysfs class device provides a standard sysfs interface
for Ambient Light Sensor devices.

Only two sysfs I/F are introduced currently.
/sys/class/als/alsX/illuminance:
	indicates the amount of light incident upon a specified surface area.
/sys/class/als/alsX/mappings:
	exports ambient light illuminance to display luminance mappings
	that can be used by an OS to calibrate its ambient light policy
	for a given sensor configuration.
	The OS can use this information to extrapolate an ALS response curve
	- noting that these values may be treated differently depending on the
	OS implementation but should be used in some form to calibrate ALS policy.

Signed-off-by: Zhang Rui <rui.zhang@...el.com>
---
 Documentation/als/sysfs.txt |  138 ++++++++++++++++++++++
 drivers/Kconfig             |    2 
 drivers/Makefile            |    1 
 drivers/als/Kconfig         |   10 +
 drivers/als/Makefile        |    5 
 drivers/als/als_sys.c       |  269 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/als_sys.h     |   57 +++++++++
 7 files changed, 482 insertions(+)

Index: linux-2.6/drivers/Kconfig
===================================================================
--- linux-2.6.orig/drivers/Kconfig
+++ linux-2.6/drivers/Kconfig
@@ -62,6 +62,8 @@ source "drivers/power/Kconfig"
 
 source "drivers/hwmon/Kconfig"
 
+source "drivers/als/Kconfig"
+
 source "drivers/thermal/Kconfig"
 
 source "drivers/watchdog/Kconfig"
Index: linux-2.6/drivers/Makefile
===================================================================
--- linux-2.6.orig/drivers/Makefile
+++ linux-2.6/drivers/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_PPS)		+= pps/
 obj-$(CONFIG_W1)		+= w1/
 obj-$(CONFIG_POWER_SUPPLY)	+= power/
 obj-$(CONFIG_HWMON)		+= hwmon/
+obj-$(CONFIG_ALS)		+= als/
 obj-$(CONFIG_THERMAL)		+= thermal/
 obj-$(CONFIG_WATCHDOG)		+= watchdog/
 obj-$(CONFIG_PHONE)		+= telephony/
Index: linux-2.6/drivers/als/Kconfig
===================================================================
--- /dev/null
+++ linux-2.6/drivers/als/Kconfig
@@ -0,0 +1,10 @@
+#
+# Ambient Light Sensor sysfs device configuration
+#
+
+menuconfig ALS
+	tristate "Ambient Light Sensor sysfs device"
+	help
+	  This framework provides a generic sysfs I/F for Ambient Light
+	  Sensor devices.
+	  If you want this support, you should say Y or M here.
Index: linux-2.6/drivers/als/Makefile
===================================================================
--- /dev/null
+++ linux-2.6/drivers/als/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for sensor chip drivers.
+#
+
+obj-$(CONFIG_ALS)		+= als_sys.o
Index: linux-2.6/drivers/als/als_sys.c
===================================================================
--- /dev/null
+++ linux-2.6/drivers/als/als_sys.c
@@ -0,0 +1,269 @@
+/*
+ *  als_sys.c - Ambient Light Sensor Sysfs support.
+ *
+ *  Copyright (C) 2009 Intel Corp
+ *  Copyright (C) 2009 Zhang Rui <rui.zhang@...el.com>
+ *
+ *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/als_sys.h>
+
+MODULE_AUTHOR("Zhang Rui");
+MODULE_DESCRIPTION("Ambient Light Sensor sysfs support");
+MODULE_LICENSE("GPL");
+
+#define PREFIX "ALS: "
+
+struct als_mapping_item {
+	struct kobject kobj;
+	int index;
+	struct list_head node;
+};
+
+/* sys I/F for Ambient Light Sensor */
+
+#define to_als_device(dev) container_of(dev, struct als_device, device)
+
+static ssize_t
+desc_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct als_device *als = to_als_device(dev);
+
+	return sprintf(buf, "%s\n", als->desc ? als->desc : "N/A");
+}
+
+static ssize_t
+illuminance_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct als_device *als = to_als_device(dev);
+	int illuminance;
+	int result;
+
+	result = als->ops->get_illuminance(als, &illuminance);
+	if (result)
+		return result;
+
+	if (!illuminance)
+		return sprintf(buf, "Illuminance below the supported range\n");
+	else if (illuminance == -1)
+		return sprintf(buf, "Illuminance above the supported range\n");
+	else if (illuminance < -1)
+		return -ERANGE;
+	else
+		return sprintf(buf, "%d\n", illuminance);
+}
+
+static DEVICE_ATTR(desc, 0444, desc_show, NULL);
+static DEVICE_ATTR(illuminance, 0444, illuminance_show, NULL);
+
+#define ATTR(_name, _mode)	\
+	struct attribute als_##_name##_attr = {	\
+		.name = __stringify(_name),	\
+		.mode = _mode,			\
+	};
+
+static ATTR(illuminance, 0444);
+static ATTR(adjustment, 0444);
+
+static struct attribute * als_mapping_attrs[] = {
+	&als_illuminance_attr,
+	&als_adjustment_attr,
+	NULL,
+};
+
+static ssize_t show_mapping_info(struct kobject *kobj,
+				       struct attribute *attr, char *buf)
+{
+	struct device *dev = container_of(kobj->parent, struct device, kobj);
+	struct als_device *als = to_als_device(dev);
+	int index, illuminance, adjustment;
+	int result;
+
+	if (!sscanf(kobj->name, "mapping%d", &index))
+		return -EINVAL;
+
+	result = als->ops->get_mapping_info(als, index, &illuminance, &adjustment);
+	if (result)
+		return result;
+
+	return sprintf(buf, "%u\n", (attr == &als_illuminance_attr) ? illuminance : adjustment);
+}
+
+static struct sysfs_ops als_mapping_info_ops = {
+	.show = show_mapping_info,
+	.store = NULL,
+};
+
+static struct kobj_type als_mapping_ktype = {
+	.sysfs_ops = &als_mapping_info_ops,
+	.default_attrs = als_mapping_attrs,
+};
+
+static void als_release(struct device *dev) {
+	struct als_device *als = to_als_device(dev);
+
+	if (als->desc)
+		kfree(als->desc);
+	kfree(als);
+}
+
+static struct class als_class = {
+	.name = "als",
+	.dev_release = als_release,
+};
+
+/**
+ * als_device_update_mappings - update the ambient light illuminance to
+ * 				display luminance adjustment mappings
+ */
+int als_device_update_mappings(struct als_device *als)
+{
+	int old_count = als->count;
+	int i;
+	struct als_mapping_item *pos, *next;
+	int result;
+
+	result = als->ops->get_mapping_count(als, &als->count);
+	if (result)
+		return result;
+
+	if (old_count == als->count)
+		return 0;
+
+	if (als->count > old_count)
+		for (i = old_count; i < als->count; i++) {
+			pos = kzalloc(sizeof(struct als_mapping_item), GFP_KERNEL);
+			if (!pos)
+				return -ENOMEM;
+
+			pos->index = i;
+			result = kobject_init_and_add(&pos->kobj, &als_mapping_ktype,
+					&als->device.kobj, "mapping%d", pos->index);
+			if (result)
+				break;
+		}
+	else
+		list_for_each_entry_safe(pos, next, &als->mappings, node) {
+			if (pos->index < als->count)
+				continue;
+			list_del(&pos->node);
+			kobject_put(&pos->kobj);
+			kfree(pos);
+		}
+
+	if (result)
+		als->count = i;
+
+	return 0;
+}
+
+EXPORT_SYMBOL(als_device_update_mappings);
+
+/**
+ * als_device_register - register a new Ambient Light Sensor class device
+ * @ops:	standard ALS devices callbacks.
+ * @devdata:	device private data.
+ */
+struct als_device *als_device_register(struct als_device_ops *ops,
+				       char *desc, void *devdata)
+{
+	struct als_device *als;
+	static int als_id;
+	int result;
+
+	if (!ops || !ops->get_illuminance)
+		return ERR_PTR(-EINVAL);
+
+	als = kzalloc(sizeof(struct als_device), GFP_KERNEL);
+	if (!als)
+		return ERR_PTR(-ENOMEM);
+
+	als->ops = ops;
+	als->device.class = &als_class;
+	als->devdata = devdata;
+	als->id = als_id++;
+	INIT_LIST_HEAD(&als->mappings);
+	if (desc) {
+		als->desc = kzalloc(strlen(desc), GFP_KERNEL);
+		if (!als->desc) {
+			kfree(als);
+			return ERR_PTR(-ENOMEM);
+		}
+		strcpy(als->desc, desc);
+	}
+	dev_set_name(&als->device, "als%d", als->id);
+	result = device_register(&als->device);
+	if (result) {
+		if (als->desc)
+			kfree(als->desc);
+		kfree(als);
+		return ERR_PTR(result);
+	}
+
+	/* sys I/F */
+	result = device_create_file(&als->device, &dev_attr_illuminance);
+	if (result)
+		goto unregister_device;
+
+	result = device_create_file(&als->device, &dev_attr_desc);
+	if (result)
+		goto unregister_device;
+
+	return als;
+
+unregister_device:
+	device_unregister(&als->device);
+	return ERR_PTR(result);
+}
+
+EXPORT_SYMBOL(als_device_register);
+
+/**
+ * als_device_unregister - removes the registered ALS device
+ * @als:	the ALS device to remove.
+ */
+void als_device_unregister(struct als_device *als)
+{
+	if (!als)
+		return;
+
+	device_remove_file(&als->device, &dev_attr_desc);
+	device_remove_file(&als->device, &dev_attr_illuminance);
+
+	device_unregister(&als->device);
+	return;
+}
+
+EXPORT_SYMBOL(als_device_unregister);
+
+static int __init als_init(void)
+{
+	return class_register(&als_class);
+}
+
+static void __exit als_exit(void)
+{
+	class_unregister(&als_class);
+}
+
+subsys_initcall(als_init);
+module_exit(als_exit);
Index: linux-2.6/include/linux/als_sys.h
===================================================================
--- /dev/null
+++ linux-2.6/include/linux/als_sys.h
@@ -0,0 +1,57 @@
+/*
+ *  als.h  ($Revision: 0 $)
+ *
+ *  Copyright (C) 2009  Intel Corp
+ *  Copyright (C) 2009  Zhang Rui <rui.zhang@...el.com>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#ifndef __ALS_SYS_H__
+#define __ALS_SYS_H__
+
+#include <linux/device.h>
+
+struct als_device;
+
+struct als_device_ops {
+	int (*get_illuminance) (struct als_device *, int *);
+	int (*get_mapping_count) (struct als_device *, int *);
+	int (*get_mapping_info) (struct als_device *, int, int *, int *);
+};
+
+struct als_mapping {
+	int illuminance;
+	int adjustment;
+};
+
+struct als_device {
+	int id;
+	int illuminance;
+	struct device device;
+	struct als_device_ops *ops;
+	void *devdata;
+	char *desc;
+	int count;
+	struct list_head mappings;
+};
+
+int als_device_update_mappings(struct als_device *als);
+struct als_device *als_device_register(struct als_device_ops *, char *, void *);
+void als_device_unregister(struct als_device *);
+
+#endif /* __ALS_SYS_H__ */
Index: linux-2.6/Documentation/als/sysfs.txt
===================================================================
--- /dev/null
+++ linux-2.6/Documentation/als/sysfs.txt
@@ -0,0 +1,138 @@
+Ambient Light Sensor Sysfs driver How To
+=========================
+
+Written by Zhang Rui <rui.zhang@...el.com>
+
+Updated: 6 August 2009
+
+Copyright (c)  2009 Intel Corporation
+
+0. Introduction
+
+The generic Ambient Light Sensor sysfs provides a standard interface for ALS devices.
+
+User space can use this interface to get the status of the ambient light environment
+the system is currently in, and get the ambient light illuminance to display luminance
+mappings to calibrate its ambient light policy for a given sensor configuration.
+
+An intelligent ALS application can make ambient light decisions based on inputs
+from these ALS attributes and adjust the LVDS brightness levels.
+
+[0-*]	denotes any positive number starting from 0
+
+Two acronyms that used in this HOW TO only:
+ALI	ambient light illuminace
+DLA	display luminance adjustment (or display brightness adjustment)
+
+1. Ambient Light Sensor sysfs driver interface functions
+
+1.1 struct als_device *als_device_register(struct als_device_ops *ops, char *desc, void *devdata)
+
+	This interface function adds a new ALS device to
+	/sys/class/als folder as als[0-*].
+
+	ops:	thermal zone device call-backs.
+		.get_illuminance: get the current ALI.
+		.get_mappings_count: get the number of ALI to DLA mappings.
+		.get_mapping_info: get the info of a specified ALI to DLA mapping.
+	desc:	a description of the ALS device.
+	devdata:device private data
+
+1.2 void als_device_unregister(struct als_device *als)
+
+	This interface function removes the ALS device.
+	It deletes the corresponding entry form /sys/class/als folder.
+
+1.3 int als_device_update_mappings(struct als_device *als)
+
+	This interface updates the ALI to DLA mappings.
+	This is usually invoked by the native ALS driver when it detects a mapping change.
+
+2. sysfs attributes structure
+
+RO	read only value
+RW	read/write value
+
+ALS sysfs attributes will be represented under /sys/class/als.
+
+/sys/class/als/als[0-*]:
+	|-----desc:			Strings which describes the ALS device
+	|-----illuminance:		Current ALI
+	|-----mapping[0-*]:
+		|-----illuminance:	ALI threshold when an DLA is needed
+		|-----adjustment:	how to do the DLA when the threshold is hit
+
+***********************************
+* Ambient Light Sendor attributes *
+***********************************
+
+desc				Strings which descibes the current ALS.
+				This is given by native ALS driver as part of registration.
+				Eg: ACPI ALS driver gives the full pathname of
+				the ALS device in ACPI namespace.
+				RO
+				Required
+
+illuminance			Current ALI reported by native ALS driver
+				Unit: lux (lumens per square meter)
+				RO
+				Required
+
+mapping[0-*]			represent one item of the ALI to DLA mappings.
+
+mapping[0-*]/illuminance	ALI threshold when an DLA is needed
+				RO
+
+mapping[0-*]/adjustment		a relative percentages in order simplify the means
+				by which these adjustments are applied in lieu of
+				changes to the user’s display brightness preference.
+				A value of 100 is used to indicate no (0%) display
+				brightness adjustment.
+				Values less than 100 indicate a negative adjustment
+				(dimming); values greater than 100 indicate a positive
+				adjustment (brightening).
+				RO
+
+3. How to implement ALS control in user space
+
+To implement the ALS control, including both ALI detection and Backlight
+adjustment, interactions between backlight driver and als driver are needed.
+It's ugly to implement such a driver in Linux kenrel.
+A user space application is preferred in this case.
+
+Below is a simple example about how to do ALS mangement in user space.
+
+This is the ACPI backlight sysfs I/F
+/sys/class/backlight/acpi_video0:
+	|-----brightness	6
+	|-----actual_brightness	6
+	|-----max_brightness	10
+
+And this is the ACPI ALS sysfs I/F
+/sys/class/als/als0:
+	|-----illuminance		500
+	|-----mapping[0]
+		|-----illuminance	0
+		|-----adjustment	50
+	|-----mapping[1]
+		|-----illuminance	200
+		|-----adjustment	70
+	|-----mapping[2]
+		|-----illuminance	600
+		|-----adjustment	100
+	|-----mapping[3]
+		|-----illuminance	900
+		|-----adjustment	125
+	|-----mapping[4]
+		|-----illuminance	1200
+		|-----adjustment	150
+
+If user thinks that brightness level 6 is good enough for him when ALI is 600,
+he can set brightness 6 as the user’s display brightness preference.
+When user goes to the base-room with the laptop and the ALI changes to 200,
+the ALS application knows that it should do a -25% display brightness
+adjustment, i.e. changes the backlight to 4.
+And when the laptop is used outdoors, where the ALI reaches 1200,
+the ALS application should do a +50% adjustment,
+i.e. run "echo 9 > /sys/class/backlight/acpi_video0/brightness".
+


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