leds-lt3593.c

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/*
 * LEDs driver for LT3593 controllers
 *
 * See the datasheet at http://cds.linear.com/docs/Datasheet/3593f.pdf
 *
 * Copyright (c) 2009 Daniel Mack <[email protected]>
 *
 * Based on leds-gpio.c,
 *
 *   Copyright (C) 2007 8D Technologies inc.
 *   Raphael Assenat <[email protected]>
 *   Copyright (C) 2008 Freescale Semiconductor, Inc.
 *
 * 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/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/leds.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/slab.h>
#include <linux/module.h>

struct lt3593_led_data {
    struct led_classdev cdev;
    unsigned gpio;
    struct work_struct work;
    u8 new_level;
};

static void lt3593_led_work(struct work_struct *work)
{
    int pulses;
    struct lt3593_led_data *led_dat =
        container_of(work, struct lt3593_led_data, work);

    /*
     * The LT3593 resets its internal current level register to the maximum
     * level on the first falling edge on the control pin. Each following
     * falling edge decreases the current level by 625uA. Up to 32 pulses
     * can be sent, so the maximum power reduction is 20mA.
     * After a timeout of 128us, the value is taken from the register and
     * applied is to the output driver.
     */

    if (led_dat->new_level == 0) {
        gpio_set_value_cansleep(led_dat->gpio, 0);
        return;
    }

    pulses = 32 - (led_dat->new_level * 32) / 255;

    if (pulses == 0) {
        gpio_set_value_cansleep(led_dat->gpio, 0);
        mdelay(1);
        gpio_set_value_cansleep(led_dat->gpio, 1);
        return;
    }

    gpio_set_value_cansleep(led_dat->gpio, 1);

    while (pulses--) {
        gpio_set_value_cansleep(led_dat->gpio, 0);
        udelay(1);
        gpio_set_value_cansleep(led_dat->gpio, 1);
        udelay(1);
    }
}

static void lt3593_led_set(struct led_classdev *led_cdev,
    enum led_brightness value)
{
    struct lt3593_led_data *led_dat =
        container_of(led_cdev, struct lt3593_led_data, cdev);

    led_dat->new_level = value;
    schedule_work(&led_dat->work);
}

static int __devinit create_lt3593_led(const struct gpio_led *template,
    struct lt3593_led_data *led_dat, struct device *parent)
{
    int ret, state;

    /* skip leds on GPIOs that aren't available */
    if (!gpio_is_valid(template->gpio)) {
        printk(KERN_INFO "%s: skipping unavailable LT3593 LED at gpio %d (%s)\n",
                KBUILD_MODNAME, template->gpio, template->name);
        return 0;
    }

    ret = gpio_request(template->gpio, template->name);
    if (ret < 0)
        return ret;

    led_dat->cdev.name = template->name;
    led_dat->cdev.default_trigger = template->default_trigger;
    led_dat->gpio = template->gpio;

    led_dat->cdev.brightness_set = lt3593_led_set;

    state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
    led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;

    if (!template->retain_state_suspended)
        led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;

    ret = gpio_direction_output(led_dat->gpio, state);
    if (ret < 0)
        goto err;

    INIT_WORK(&led_dat->work, lt3593_led_work);

    ret = led_classdev_register(parent, &led_dat->cdev);
    if (ret < 0)
        goto err;

    printk(KERN_INFO "%s: registered LT3593 LED '%s' at GPIO %d\n",
        KBUILD_MODNAME, template->name, template->gpio);

    return 0;

err:
    gpio_free(led_dat->gpio);
    return ret;
}

static void delete_lt3593_led(struct lt3593_led_data *led)
{
    if (!gpio_is_valid(led->gpio))
        return;

    led_classdev_unregister(&led->cdev);
    cancel_work_sync(&led->work);
    gpio_free(led->gpio);
}

static int __devinit lt3593_led_probe(struct platform_device *pdev)
{
    struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
    struct lt3593_led_data *leds_data;
    int i, ret = 0;

    if (!pdata)
        return -EBUSY;

    leds_data = devm_kzalloc(&pdev->dev,
            sizeof(struct lt3593_led_data) * pdata->num_leds,
            GFP_KERNEL);
    if (!leds_data)
        return -ENOMEM;

    for (i = 0; i < pdata->num_leds; i++) {
        ret = create_lt3593_led(&pdata->leds[i], &leds_data[i],
                      &pdev->dev);
        if (ret < 0)
            goto err;
    }

    platform_set_drvdata(pdev, leds_data);

    return 0;

err:
    for (i = i - 1; i >= 0; i--)
        delete_lt3593_led(&leds_data[i]);

    return ret;
}

static int __devexit lt3593_led_remove(struct platform_device *pdev)
{
    int i;
    struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
    struct lt3593_led_data *leds_data;

    leds_data = platform_get_drvdata(pdev);

    for (i = 0; i < pdata->num_leds; i++)
        delete_lt3593_led(&leds_data[i]);

    return 0;
}

static struct platform_driver lt3593_led_driver = {
    .probe      = lt3593_led_probe,
    .remove     = __devexit_p(lt3593_led_remove),
    .driver     = {
        .name   = "leds-lt3593",
        .owner  = THIS_MODULE,
    },
};

module_platform_driver(lt3593_led_driver);

MODULE_AUTHOR("Daniel Mack <[email protected]>");
MODULE_DESCRIPTION("LED driver for LT3593 controllers");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:leds-lt3593");