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228 lines
6.3 KiB
228 lines
6.3 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Backlight driver for the Kinetic KTD253 |
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* Based on code and know-how from the Samsung GT-S7710 |
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* Gareth Phillips <[email protected]> |
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*/ |
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#include <linux/backlight.h> |
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#include <linux/delay.h> |
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#include <linux/err.h> |
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#include <linux/fb.h> |
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#include <linux/gpio/consumer.h> |
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#include <linux/init.h> |
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#include <linux/kernel.h> |
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#include <linux/limits.h> |
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#include <linux/module.h> |
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#include <linux/of.h> |
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#include <linux/platform_device.h> |
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#include <linux/property.h> |
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#include <linux/slab.h> |
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/* Current ratio is n/32 from 1/32 to 32/32 */ |
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#define KTD253_MIN_RATIO 1 |
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#define KTD253_MAX_RATIO 32 |
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#define KTD253_DEFAULT_RATIO 13 |
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#define KTD253_T_LOW_NS (200 + 10) /* Additional 10ns as safety factor */ |
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#define KTD253_T_HIGH_NS (200 + 10) /* Additional 10ns as safety factor */ |
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#define KTD253_T_OFF_CRIT_NS 100000 /* 100 us, now it doesn't look good */ |
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#define KTD253_T_OFF_MS 3 |
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struct ktd253_backlight { |
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struct device *dev; |
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struct backlight_device *bl; |
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struct gpio_desc *gpiod; |
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u16 ratio; |
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}; |
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static void ktd253_backlight_set_max_ratio(struct ktd253_backlight *ktd253) |
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{ |
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gpiod_set_value_cansleep(ktd253->gpiod, 1); |
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ndelay(KTD253_T_HIGH_NS); |
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/* We always fall back to this when we power on */ |
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} |
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static int ktd253_backlight_stepdown(struct ktd253_backlight *ktd253) |
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{ |
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/* |
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* These GPIO operations absolutely can NOT sleep so no _cansleep |
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* suffixes, and no using GPIO expanders on slow buses for this! |
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* |
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* The maximum number of cycles of the loop is 32 so the time taken |
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* should nominally be: |
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* (T_LOW_NS + T_HIGH_NS + loop_time) * 32 |
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* |
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* Architectures do not always support ndelay() and we will get a few us |
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* instead. If we get to a critical time limit an interrupt has likely |
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* occured in the low part of the loop and we need to restart from the |
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* top so we have the backlight in a known state. |
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*/ |
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u64 ns; |
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ns = ktime_get_ns(); |
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gpiod_set_value(ktd253->gpiod, 0); |
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ndelay(KTD253_T_LOW_NS); |
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gpiod_set_value(ktd253->gpiod, 1); |
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ns = ktime_get_ns() - ns; |
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if (ns >= KTD253_T_OFF_CRIT_NS) { |
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dev_err(ktd253->dev, "PCM on backlight took too long (%llu ns)\n", ns); |
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return -EAGAIN; |
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} |
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ndelay(KTD253_T_HIGH_NS); |
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return 0; |
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} |
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static int ktd253_backlight_update_status(struct backlight_device *bl) |
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{ |
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struct ktd253_backlight *ktd253 = bl_get_data(bl); |
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int brightness = backlight_get_brightness(bl); |
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u16 target_ratio; |
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u16 current_ratio = ktd253->ratio; |
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int ret; |
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dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness); |
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target_ratio = brightness; |
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if (target_ratio == current_ratio) |
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/* This is already right */ |
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return 0; |
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if (target_ratio == 0) { |
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gpiod_set_value_cansleep(ktd253->gpiod, 0); |
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/* |
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* We need to keep the GPIO low for at least this long |
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* to actually switch the KTD253 off. |
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*/ |
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msleep(KTD253_T_OFF_MS); |
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ktd253->ratio = 0; |
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return 0; |
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} |
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if (current_ratio == 0) { |
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ktd253_backlight_set_max_ratio(ktd253); |
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current_ratio = KTD253_MAX_RATIO; |
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} |
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while (current_ratio != target_ratio) { |
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/* |
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* These GPIO operations absolutely can NOT sleep so no |
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* _cansleep suffixes, and no using GPIO expanders on |
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* slow buses for this! |
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*/ |
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ret = ktd253_backlight_stepdown(ktd253); |
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if (ret == -EAGAIN) { |
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/* |
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* Something disturbed the backlight setting code when |
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* running so we need to bring the PWM back to a known |
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* state. This shouldn't happen too much. |
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*/ |
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gpiod_set_value_cansleep(ktd253->gpiod, 0); |
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msleep(KTD253_T_OFF_MS); |
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ktd253_backlight_set_max_ratio(ktd253); |
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current_ratio = KTD253_MAX_RATIO; |
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} else if (current_ratio == KTD253_MIN_RATIO) { |
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/* After 1/32 we loop back to 32/32 */ |
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current_ratio = KTD253_MAX_RATIO; |
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} else { |
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current_ratio--; |
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} |
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} |
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ktd253->ratio = current_ratio; |
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dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio); |
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return 0; |
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} |
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static const struct backlight_ops ktd253_backlight_ops = { |
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.options = BL_CORE_SUSPENDRESUME, |
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.update_status = ktd253_backlight_update_status, |
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}; |
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static int ktd253_backlight_probe(struct platform_device *pdev) |
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{ |
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struct device *dev = &pdev->dev; |
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struct backlight_device *bl; |
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struct ktd253_backlight *ktd253; |
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u32 max_brightness; |
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u32 brightness; |
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int ret; |
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ktd253 = devm_kzalloc(dev, sizeof(*ktd253), GFP_KERNEL); |
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if (!ktd253) |
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return -ENOMEM; |
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ktd253->dev = dev; |
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ret = device_property_read_u32(dev, "max-brightness", &max_brightness); |
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if (ret) |
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max_brightness = KTD253_MAX_RATIO; |
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if (max_brightness > KTD253_MAX_RATIO) { |
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/* Clamp brightness to hardware max */ |
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dev_err(dev, "illegal max brightness specified\n"); |
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max_brightness = KTD253_MAX_RATIO; |
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} |
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ret = device_property_read_u32(dev, "default-brightness", &brightness); |
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if (ret) |
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brightness = KTD253_DEFAULT_RATIO; |
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if (brightness > max_brightness) { |
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/* Clamp default brightness to max brightness */ |
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dev_err(dev, "default brightness exceeds max brightness\n"); |
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brightness = max_brightness; |
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} |
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ktd253->gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW); |
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if (IS_ERR(ktd253->gpiod)) { |
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ret = PTR_ERR(ktd253->gpiod); |
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if (ret != -EPROBE_DEFER) |
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dev_err(dev, "gpio line missing or invalid.\n"); |
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return ret; |
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} |
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gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev)); |
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/* Bring backlight to a known off state */ |
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msleep(KTD253_T_OFF_MS); |
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bl = devm_backlight_device_register(dev, dev_name(dev), dev, ktd253, |
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&ktd253_backlight_ops, NULL); |
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if (IS_ERR(bl)) { |
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dev_err(dev, "failed to register backlight\n"); |
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return PTR_ERR(bl); |
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} |
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bl->props.max_brightness = max_brightness; |
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/* When we just enable the GPIO line we set max brightness */ |
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if (brightness) { |
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bl->props.brightness = brightness; |
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bl->props.power = FB_BLANK_UNBLANK; |
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} else { |
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bl->props.brightness = 0; |
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bl->props.power = FB_BLANK_POWERDOWN; |
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} |
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ktd253->bl = bl; |
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platform_set_drvdata(pdev, bl); |
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backlight_update_status(bl); |
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return 0; |
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} |
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static const struct of_device_id ktd253_backlight_of_match[] = { |
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{ .compatible = "kinetic,ktd253" }, |
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{ .compatible = "kinetic,ktd259" }, |
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{ /* sentinel */ } |
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}; |
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MODULE_DEVICE_TABLE(of, ktd253_backlight_of_match); |
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static struct platform_driver ktd253_backlight_driver = { |
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.driver = { |
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.name = "ktd253-backlight", |
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.of_match_table = ktd253_backlight_of_match, |
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}, |
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.probe = ktd253_backlight_probe, |
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}; |
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module_platform_driver(ktd253_backlight_driver); |
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MODULE_AUTHOR("Linus Walleij <[email protected]>"); |
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MODULE_DESCRIPTION("Kinetic KTD253 Backlight Driver"); |
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MODULE_LICENSE("GPL"); |
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MODULE_ALIAS("platform:ktd253-backlight");
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