1 /* 2 * gpio_backlight.c - Simple GPIO-controlled backlight 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 */ 8 9 #include <linux/backlight.h> 10 #include <linux/err.h> 11 #include <linux/fb.h> 12 #include <linux/gpio.h> 13 #include <linux/init.h> 14 #include <linux/kernel.h> 15 #include <linux/module.h> 16 #include <linux/of.h> 17 #include <linux/of_gpio.h> 18 #include <linux/platform_data/gpio_backlight.h> 19 #include <linux/platform_device.h> 20 #include <linux/slab.h> 21 22 struct gpio_backlight { 23 struct device *dev; 24 struct device *fbdev; 25 26 int gpio; 27 int active; 28 int def_value; 29 }; 30 31 static int gpio_backlight_update_status(struct backlight_device *bl) 32 { 33 struct gpio_backlight *gbl = bl_get_data(bl); 34 int brightness = bl->props.brightness; 35 36 if (bl->props.power != FB_BLANK_UNBLANK || 37 bl->props.fb_blank != FB_BLANK_UNBLANK || 38 bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK)) 39 brightness = 0; 40 41 gpio_set_value_cansleep(gbl->gpio, 42 brightness ? gbl->active : !gbl->active); 43 44 return 0; 45 } 46 47 static int gpio_backlight_get_brightness(struct backlight_device *bl) 48 { 49 return bl->props.brightness; 50 } 51 52 static int gpio_backlight_check_fb(struct backlight_device *bl, 53 struct fb_info *info) 54 { 55 struct gpio_backlight *gbl = bl_get_data(bl); 56 57 return gbl->fbdev == NULL || gbl->fbdev == info->dev; 58 } 59 60 static const struct backlight_ops gpio_backlight_ops = { 61 .options = BL_CORE_SUSPENDRESUME, 62 .update_status = gpio_backlight_update_status, 63 .get_brightness = gpio_backlight_get_brightness, 64 .check_fb = gpio_backlight_check_fb, 65 }; 66 67 static int gpio_backlight_probe_dt(struct platform_device *pdev, 68 struct gpio_backlight *gbl) 69 { 70 struct device_node *np = pdev->dev.of_node; 71 enum of_gpio_flags gpio_flags; 72 73 gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags); 74 75 if (!gpio_is_valid(gbl->gpio)) { 76 if (gbl->gpio != -EPROBE_DEFER) { 77 dev_err(&pdev->dev, 78 "Error: The gpios parameter is missing or invalid.\n"); 79 } 80 return gbl->gpio; 81 } 82 83 gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1; 84 85 gbl->def_value = of_property_read_bool(np, "default-on"); 86 87 return 0; 88 } 89 90 static int gpio_backlight_probe(struct platform_device *pdev) 91 { 92 struct gpio_backlight_platform_data *pdata = 93 dev_get_platdata(&pdev->dev); 94 struct backlight_properties props; 95 struct backlight_device *bl; 96 struct gpio_backlight *gbl; 97 struct device_node *np = pdev->dev.of_node; 98 int ret; 99 100 if (!pdata && !np) { 101 dev_err(&pdev->dev, 102 "failed to find platform data or device tree node.\n"); 103 return -ENODEV; 104 } 105 106 gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL); 107 if (gbl == NULL) 108 return -ENOMEM; 109 110 gbl->dev = &pdev->dev; 111 112 if (np) { 113 ret = gpio_backlight_probe_dt(pdev, gbl); 114 if (ret) 115 return ret; 116 } else { 117 gbl->fbdev = pdata->fbdev; 118 gbl->gpio = pdata->gpio; 119 gbl->active = pdata->active_low ? 0 : 1; 120 gbl->def_value = pdata->def_value; 121 } 122 123 ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT | 124 (gbl->active ? GPIOF_INIT_LOW 125 : GPIOF_INIT_HIGH), 126 pdata ? pdata->name : "backlight"); 127 if (ret < 0) { 128 dev_err(&pdev->dev, "unable to request GPIO\n"); 129 return ret; 130 } 131 132 memset(&props, 0, sizeof(props)); 133 props.type = BACKLIGHT_RAW; 134 props.max_brightness = 1; 135 bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev), 136 &pdev->dev, gbl, &gpio_backlight_ops, 137 &props); 138 if (IS_ERR(bl)) { 139 dev_err(&pdev->dev, "failed to register backlight\n"); 140 return PTR_ERR(bl); 141 } 142 143 bl->props.brightness = gbl->def_value; 144 backlight_update_status(bl); 145 146 platform_set_drvdata(pdev, bl); 147 return 0; 148 } 149 150 #ifdef CONFIG_OF 151 static struct of_device_id gpio_backlight_of_match[] = { 152 { .compatible = "gpio-backlight" }, 153 { /* sentinel */ } 154 }; 155 #endif 156 157 static struct platform_driver gpio_backlight_driver = { 158 .driver = { 159 .name = "gpio-backlight", 160 .owner = THIS_MODULE, 161 .of_match_table = of_match_ptr(gpio_backlight_of_match), 162 }, 163 .probe = gpio_backlight_probe, 164 }; 165 166 module_platform_driver(gpio_backlight_driver); 167 168 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 169 MODULE_DESCRIPTION("GPIO-based Backlight Driver"); 170 MODULE_LICENSE("GPL"); 171 MODULE_ALIAS("platform:gpio-backlight"); 172