backlight: Add GPIO-based backlight driver

The GPIO backlight driver controls the backlight in on/off mode through
a single GPIO.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

drivers/video/backlight/Kconfig

@@ -425,6 +425,13 @@ config BACKLIGHT_AS3711
 	  If you have an Austrian Microsystems AS3711 say Y to enable the
 	  backlight driver.
 
+config BACKLIGHT_GPIO
+	tristate "Generic GPIO based Backlight Driver"
+	depends on GPIOLIB
+	help
+	  If you have a LCD backlight adjustable by GPIO, say Y to enable
+	  this driver.
+
 endif # BACKLIGHT_CLASS_DEVICE
 
 endif # BACKLIGHT_LCD_SUPPORT

drivers/video/backlight/Makefile

@@ -32,6 +32,7 @@ obj-$(CONFIG_BACKLIGHT_DA903X)		+= da903x_bl.o
 obj-$(CONFIG_BACKLIGHT_DA9052)		+= da9052_bl.o
 obj-$(CONFIG_BACKLIGHT_EP93XX)		+= ep93xx_bl.o
 obj-$(CONFIG_BACKLIGHT_GENERIC)		+= generic_bl.o
+obj-$(CONFIG_BACKLIGHT_GPIO)		+= gpio_backlight.o
 obj-$(CONFIG_BACKLIGHT_HP680)		+= hp680_bl.o
 obj-$(CONFIG_BACKLIGHT_HP700)		+= jornada720_bl.o
 obj-$(CONFIG_BACKLIGHT_LM3533)		+= lm3533_bl.o

drivers/video/backlight/gpio_backlight.c

+/*
+ * gpio_backlight.c - Simple GPIO-controlled backlight
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/fb.h>
+#include <linux/gpio.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_data/gpio_backlight.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+struct gpio_backlight {
+	struct device *dev;
+	struct device *fbdev;
+
+	int gpio;
+	int active;
+};
+
+static int gpio_backlight_update_status(struct backlight_device *bl)
+{
+	struct gpio_backlight *gbl = bl_get_data(bl);
+	int brightness = bl->props.brightness;
+
+	if (bl->props.power != FB_BLANK_UNBLANK ||
+	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
+	    bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
+		brightness = 0;
+
+	gpio_set_value(gbl->gpio, brightness ? gbl->active : !gbl->active);
+
+	return 0;
+}
+
+static int gpio_backlight_get_brightness(struct backlight_device *bl)
+{
+	return bl->props.brightness;
+}
+
+static int gpio_backlight_check_fb(struct backlight_device *bl,
+				   struct fb_info *info)
+{
+	struct gpio_backlight *gbl = bl_get_data(bl);
+
+	return gbl->fbdev == NULL || gbl->fbdev == info->dev;
+}
+
+static const struct backlight_ops gpio_backlight_ops = {
+	.options	= BL_CORE_SUSPENDRESUME,
+	.update_status	= gpio_backlight_update_status,
+	.get_brightness	= gpio_backlight_get_brightness,
+	.check_fb	= gpio_backlight_check_fb,
+};
+
+static int gpio_backlight_probe(struct platform_device *pdev)
+{
+	struct gpio_backlight_platform_data *pdata = pdev->dev.platform_data;
+	struct backlight_properties props;
+	struct backlight_device *bl;
+	struct gpio_backlight *gbl;
+	int ret;
+
+	if (!pdata) {
+		dev_err(&pdev->dev, "failed to find platform data\n");
+		return -ENODEV;
+	}
+
+	gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
+	if (gbl == NULL)
+		return -ENOMEM;
+
+	gbl->dev = &pdev->dev;
+	gbl->fbdev = pdata->fbdev;
+	gbl->gpio = pdata->gpio;
+	gbl->active = pdata->active_low ? 0 : 1;
+
+	ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
+				    (gbl->active ? GPIOF_INIT_LOW
+						 : GPIOF_INIT_HIGH),
+				    pdata->name);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "unable to request GPIO\n");
+		return ret;
+	}
+
+	memset(&props, 0, sizeof(props));
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = 1;
+	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, gbl,
+				       &gpio_backlight_ops, &props);
+	if (IS_ERR(bl)) {
+		dev_err(&pdev->dev, "failed to register backlight\n");
+		return PTR_ERR(bl);
+	}
+
+	bl->props.brightness = pdata->def_value;
+	backlight_update_status(bl);
+
+	platform_set_drvdata(pdev, bl);
+	return 0;
+}
+
+static int gpio_backlight_remove(struct platform_device *pdev)
+{
+	struct backlight_device *bl = platform_get_drvdata(pdev);
+
+	backlight_device_unregister(bl);
+	return 0;
+}
+
+static struct platform_driver gpio_backlight_driver = {
+	.driver		= {
+		.name		= "gpio-backlight",
+		.owner		= THIS_MODULE,
+	},
+	.probe		= gpio_backlight_probe,
+	.remove		= gpio_backlight_remove,
+};
+
+module_platform_driver(gpio_backlight_driver);
+
+MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
+MODULE_DESCRIPTION("GPIO-based Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:gpio-backlight");

include/linux/platform_data/gpio_backlight.h

+/*
+ * gpio_backlight.h - Simple GPIO-controlled backlight
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#ifndef __GPIO_BACKLIGHT_H__
+#define __GPIO_BACKLIGHT_H__
+
+struct device;
+
+struct gpio_backlight_platform_data {
+	struct device *fbdev;
+	int gpio;
+	int def_value;
+	bool active_low;
+	const char *name;
+};
+
+#endif