+// SPDX-License-Identifier: GPL-2.0-only
/*
* 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/of_gpio.h>
#include <linux/platform_data/gpio_backlight.h>
#include <linux/platform_device.h>
+ #include <linux/property.h>
#include <linux/slab.h>
struct gpio_backlight {
struct gpio_backlight *gbl)
{
struct device *dev = &pdev->dev;
- struct device_node *np = dev->of_node;
enum gpiod_flags flags;
int ret;
- gbl->def_value = of_property_read_bool(np, "default-on");
+ gbl->def_value = device_property_read_bool(dev, "default-on");
flags = gbl->def_value ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
gbl->gpiod = devm_gpiod_get(dev, NULL, flags);
struct backlight_properties props;
struct backlight_device *bl;
struct gpio_backlight *gbl;
- struct device_node *np = pdev->dev.of_node;
int ret;
- if (!pdata && !np) {
- dev_err(&pdev->dev,
- "failed to find platform data or device tree node.\n");
- return -ENODEV;
- }
-
gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
if (gbl == NULL)
return -ENOMEM;
gbl->dev = &pdev->dev;
- if (np) {
+ if (pdev->dev.fwnode) {
ret = gpio_backlight_probe_dt(pdev, gbl);
if (ret)
return ret;
- } else {
+ } else if (pdata) {
/*
* Legacy platform data GPIO retrieveal. Do not expand
* the use of this code path, currently only used by one
gbl->gpiod = gpio_to_desc(pdata->gpio);
if (!gbl->gpiod)
return -EINVAL;
+ } else {
+ dev_err(&pdev->dev,
+ "failed to find platform data or device tree node.\n");
+ return -ENODEV;
}
memset(&props, 0, sizeof(props));
return 0;
}
- #ifdef CONFIG_OF
static struct of_device_id gpio_backlight_of_match[] = {
{ .compatible = "gpio-backlight" },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
- #endif
static struct platform_driver gpio_backlight_driver = {
.driver = {
.name = "gpio-backlight",
- .of_match_table = of_match_ptr(gpio_backlight_of_match),
+ .of_match_table = gpio_backlight_of_match,
},
.probe = gpio_backlight_probe,
};
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
/*
- * linux/drivers/video/backlight/pwm_bl.c
- *
- * simple PWM based backlight control, board code has to setup
+ * Simple PWM based backlight control, board code has to setup
* 1) pin configuration so PWM waveforms can output
* 2) platform_data being correctly configured
*/
struct platform_pwm_backlight_data *data,
unsigned int period)
{
- unsigned int counter = 0;
- unsigned int i, n;
+ unsigned int i;
u64 retval;
/*
- * Count the number of bits needed to represent the period number. The
- * number of bits is used to calculate the number of levels used for the
- * brightness-levels table, the purpose of this calculation is have a
- * pre-computed table with enough levels to get linear brightness
- * perception. The period is divided by the number of bits so for a
- * 8-bit PWM we have 255 / 8 = 32 brightness levels or for a 16-bit PWM
- * we have 65535 / 16 = 4096 brightness levels.
- *
- * Note that this method is based on empirical testing on different
- * devices with PWM of 8 and 16 bits of resolution.
+ * Once we have 4096 levels there's little point going much higher...
+ * neither interactive sliders nor animation benefits from having
+ * more values in the table.
*/
- n = period;
- while (n) {
- counter += n % 2;
- n >>= 1;
- }
+ data->max_brightness =
+ min((int)DIV_ROUND_UP(period, fls(period)), 4096);
- data->max_brightness = DIV_ROUND_UP(period, counter);
data->levels = devm_kcalloc(dev, data->max_brightness,
sizeof(*data->levels), GFP_KERNEL);
if (!data->levels)
module_platform_driver(pwm_backlight_driver);
MODULE_DESCRIPTION("PWM based Backlight Driver");
- MODULE_LICENSE("GPL");
+ MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:pwm-backlight");