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> /* Only for legacy support */ 13 #include <linux/gpio/consumer.h> 14 #include <linux/init.h> 15 #include <linux/kernel.h> 16 #include <linux/module.h> 17 #include <linux/of.h> 18 #include <linux/of_gpio.h> 19 #include <linux/platform_data/gpio_backlight.h> 20 #include <linux/platform_device.h> 21 #include <linux/slab.h> 22 23 struct gpio_backlight { 24 struct device *dev; 25 struct device *fbdev; 26 27 struct gpio_desc *gpiod; 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 gpiod_set_value_cansleep(gbl->gpiod, brightness); 42 43 return 0; 44 } 45 46 static int gpio_backlight_check_fb(struct backlight_device *bl, 47 struct fb_info *info) 48 { 49 struct gpio_backlight *gbl = bl_get_data(bl); 50 51 return gbl->fbdev == NULL || gbl->fbdev == info->dev; 52 } 53 54 static const struct backlight_ops gpio_backlight_ops = { 55 .options = BL_CORE_SUSPENDRESUME, 56 .update_status = gpio_backlight_update_status, 57 .check_fb = gpio_backlight_check_fb, 58 }; 59 60 static int gpio_backlight_probe_dt(struct platform_device *pdev, 61 struct gpio_backlight *gbl) 62 { 63 struct device *dev = &pdev->dev; 64 struct device_node *np = dev->of_node; 65 enum gpiod_flags flags; 66 int ret; 67 68 gbl->def_value = of_property_read_bool(np, "default-on"); 69 flags = gbl->def_value ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW; 70 71 gbl->gpiod = devm_gpiod_get(dev, NULL, flags); 72 if (IS_ERR(gbl->gpiod)) { 73 ret = PTR_ERR(gbl->gpiod); 74 75 if (ret != -EPROBE_DEFER) { 76 dev_err(dev, 77 "Error: The gpios parameter is missing or invalid.\n"); 78 } 79 return ret; 80 } 81 82 return 0; 83 } 84 85 static int gpio_backlight_probe(struct platform_device *pdev) 86 { 87 struct gpio_backlight_platform_data *pdata = 88 dev_get_platdata(&pdev->dev); 89 struct backlight_properties props; 90 struct backlight_device *bl; 91 struct gpio_backlight *gbl; 92 struct device_node *np = pdev->dev.of_node; 93 int ret; 94 95 if (!pdata && !np) { 96 dev_err(&pdev->dev, 97 "failed to find platform data or device tree node.\n"); 98 return -ENODEV; 99 } 100 101 gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL); 102 if (gbl == NULL) 103 return -ENOMEM; 104 105 gbl->dev = &pdev->dev; 106 107 if (np) { 108 ret = gpio_backlight_probe_dt(pdev, gbl); 109 if (ret) 110 return ret; 111 } else { 112 /* 113 * Legacy platform data GPIO retrieveal. Do not expand 114 * the use of this code path, currently only used by one 115 * SH board. 116 */ 117 unsigned long flags = GPIOF_DIR_OUT; 118 119 gbl->fbdev = pdata->fbdev; 120 gbl->def_value = pdata->def_value; 121 flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW; 122 123 ret = devm_gpio_request_one(gbl->dev, pdata->gpio, flags, 124 pdata ? pdata->name : "backlight"); 125 if (ret < 0) { 126 dev_err(&pdev->dev, "unable to request GPIO\n"); 127 return ret; 128 } 129 gbl->gpiod = gpio_to_desc(pdata->gpio); 130 if (!gbl->gpiod) 131 return -EINVAL; 132 } 133 134 memset(&props, 0, sizeof(props)); 135 props.type = BACKLIGHT_RAW; 136 props.max_brightness = 1; 137 bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev), 138 &pdev->dev, gbl, &gpio_backlight_ops, 139 &props); 140 if (IS_ERR(bl)) { 141 dev_err(&pdev->dev, "failed to register backlight\n"); 142 return PTR_ERR(bl); 143 } 144 145 bl->props.brightness = gbl->def_value; 146 backlight_update_status(bl); 147 148 platform_set_drvdata(pdev, bl); 149 return 0; 150 } 151 152 #ifdef CONFIG_OF 153 static struct of_device_id gpio_backlight_of_match[] = { 154 { .compatible = "gpio-backlight" }, 155 { /* sentinel */ } 156 }; 157 158 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match); 159 #endif 160 161 static struct platform_driver gpio_backlight_driver = { 162 .driver = { 163 .name = "gpio-backlight", 164 .of_match_table = of_match_ptr(gpio_backlight_of_match), 165 }, 166 .probe = gpio_backlight_probe, 167 }; 168 169 module_platform_driver(gpio_backlight_driver); 170 171 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 172 MODULE_DESCRIPTION("GPIO-based Backlight Driver"); 173 MODULE_LICENSE("GPL"); 174 MODULE_ALIAS("platform:gpio-backlight"); 175