[PATCH 3/9] Loongson: YeeLoong: add backlight driver

[Wu Zhangjin <wuzhangjin@gmail.com>]

This patch adds YeeLoong Backlight Driver, it provides standard
interface(/sys/class/backlight/) for user-space applications(e.g.
kpowersave, gnome-power-manager) to control the brightness of the
backlight.

Signed-off-by: Zhou Yajin <yajinzhou@vm-kernel.org>
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
 drivers/platform/mips/Kconfig           |    1 +
 drivers/platform/mips/yeeloong_laptop.c |   83 +++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+), 0 deletions(-)

diff --git a/drivers/platform/mips/Kconfig b/drivers/platform/mips/Kconfig
index 5ac5215..c1ba03d 100644
--- a/drivers/platform/mips/Kconfig
+++ b/drivers/platform/mips/Kconfig
@@ -17,6 +17,7 @@ if MIPS_PLATFORM_DEVICES
 config LEMOTE_YEELOONG2F
 	tristate "Lemote YeeLoong Laptop"
 	depends on LEMOTE_MACH2F
+	select BACKLIGHT_CLASS_DEVICE
 	help
 	  YeeLoong netbook is a mini laptop made by Lemote, which is basically
 	  compatible to FuLoong2F mini PC, but it has an extra Embedded
diff --git a/drivers/platform/mips/yeeloong_laptop.c b/drivers/platform/mips/yeeloong_laptop.c
index 09f606c..0ec8c03 100644
--- a/drivers/platform/mips/yeeloong_laptop.c
+++ b/drivers/platform/mips/yeeloong_laptop.c
@@ -10,6 +10,81 @@
 
 #include <linux/err.h>
 #include <linux/platform_device.h>
+#include <linux/backlight.h>	/* for backlight subdriver */
+#include <linux/fb.h>
+
+#include <ec_kb3310b.h>
+
+/* backlight subdriver */
+#define MAX_BRIGHTNESS	8
+
+static int yeeloong_set_brightness(struct backlight_device *bd)
+{
+	unsigned int level, current_level;
+	static unsigned int old_level;
+
+	level = (bd->props.fb_blank == FB_BLANK_UNBLANK &&
+		 bd->props.power == FB_BLANK_UNBLANK) ?
+	    bd->props.brightness : 0;
+
+	if (level > MAX_BRIGHTNESS)
+		level = MAX_BRIGHTNESS;
+	else if (level < 0)
+		level = 0;
+
+	/* Avoid to modify the brightness when EC is tuning it */
+	if (old_level != level) {
+		current_level = ec_read(REG_DISPLAY_BRIGHTNESS);
+		if (old_level == current_level)
+			ec_write(REG_DISPLAY_BRIGHTNESS, level);
+		old_level = level;
+	}
+
+	return 0;
+}
+
+static int yeeloong_get_brightness(struct backlight_device *bd)
+{
+	return ec_read(REG_DISPLAY_BRIGHTNESS);
+}
+
+static const struct backlight_ops backlight_ops = {
+	.get_brightness = yeeloong_get_brightness,
+	.update_status = yeeloong_set_brightness,
+};
+
+static struct backlight_device *yeeloong_backlight_dev;
+
+static int yeeloong_backlight_init(void)
+{
+	int ret;
+	struct backlight_properties props;
+
+	memset(&props, 0, sizeof(struct backlight_properties));
+	props.max_brightness = MAX_BRIGHTNESS;
+	yeeloong_backlight_dev = backlight_device_register("backlight0", NULL,
+			NULL, &backlight_ops, &props);
+
+	if (IS_ERR(yeeloong_backlight_dev)) {
+		ret = PTR_ERR(yeeloong_backlight_dev);
+		yeeloong_backlight_dev = NULL;
+		return ret;
+	}
+
+	yeeloong_backlight_dev->props.brightness =
+		yeeloong_get_brightness(yeeloong_backlight_dev);
+	backlight_update_status(yeeloong_backlight_dev);
+
+	return 0;
+}
+
+static void yeeloong_backlight_exit(void)
+{
+	if (yeeloong_backlight_dev) {
+		backlight_device_unregister(yeeloong_backlight_dev);
+		yeeloong_backlight_dev = NULL;
+	}
+}
 
 static struct platform_device_id platform_device_ids[] = {
 	{
@@ -41,11 +116,19 @@ static int __init yeeloong_init(void)
 		return ret;
 	}
 
+	ret = yeeloong_backlight_init();
+	if (ret) {
+		pr_err("Fail to register yeeloong backlight driver.\n");
+		yeeloong_backlight_exit();
+		return ret;
+	}
+
 	return 0;
 }
 
 static void __exit yeeloong_exit(void)
 {
+	yeeloong_backlight_exit();
 	platform_driver_unregister(&platform_driver);
 
 	pr_info("Unload YeeLoong Platform Specific Driver.\n");
-- 
1.7.0.4