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* leds-lp3944.c - driver for National Semiconductor LP3944 Funlight Chip
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* Copyright (C) 2009 Antonio Ospite <ospite@studenti.unina.it>
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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* I2C driver for National Semiconductor LP3944 Funlight Chip
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* http://www.national.com/pf/LP/LP3944.html
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* This helper chip can drive up to 8 leds, with two programmable DIM modes;
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* it could even be used as a gpio expander but this driver assumes it is used
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* as a led controller.
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* The DIM modes are used to set _blink_ patterns for leds, the pattern is
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* specified supplying two parameters:
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* - period: from 0s to 1.6s
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* - duty cycle: percentage of the period the led is on, from 0 to 100
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* LP3944 can be found on Motorola A910 smartphone, where it drives the rgb
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* leds, the camera flash light and the displays backlights.
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#include <linux/module.h>
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#include <linux/i2c.h>
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#include <linux/slab.h>
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#include <linux/leds.h>
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#include <linux/mutex.h>
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#include <linux/workqueue.h>
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#include <linux/leds-lp3944.h>
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/* Read Only Registers */
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#define LP3944_REG_INPUT1 0x00 /* LEDs 0-7 InputRegister (Read Only) */
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#define LP3944_REG_REGISTER1 0x01 /* None (Read Only) */
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#define LP3944_REG_PSC0 0x02 /* Frequency Prescaler 0 (R/W) */
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#define LP3944_REG_PWM0 0x03 /* PWM Register 0 (R/W) */
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#define LP3944_REG_PSC1 0x04 /* Frequency Prescaler 1 (R/W) */
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#define LP3944_REG_PWM1 0x05 /* PWM Register 1 (R/W) */
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#define LP3944_REG_LS0 0x06 /* LEDs 0-3 Selector (R/W) */
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#define LP3944_REG_LS1 0x07 /* LEDs 4-7 Selector (R/W) */
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/* These registers are not used to control leds in LP3944, they can store
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* arbitrary values which the chip will ignore.
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#define LP3944_REG_REGISTER8 0x08
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#define LP3944_REG_REGISTER9 0x09
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#define LP3944_PERIOD_MIN 0
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#define LP3944_PERIOD_MAX 1600
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/* duty cycle is a percentage */
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#define LP3944_DUTY_CYCLE_MIN 0
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#define LP3944_DUTY_CYCLE_MAX 100
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#define ldev_to_led(c) container_of(c, struct lp3944_led_data, ldev)
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struct lp3944_led_data {
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enum lp3944_type type;
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enum lp3944_status status;
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struct led_classdev ldev;
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struct i2c_client *client;
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struct work_struct work;
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struct i2c_client *client;
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struct lp3944_led_data leds[LP3944_LEDS_MAX];
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static int lp3944_reg_read(struct i2c_client *client, u8 reg, u8 *value)
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tmp = i2c_smbus_read_byte_data(client, reg);
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static int lp3944_reg_write(struct i2c_client *client, u8 reg, u8 value)
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return i2c_smbus_write_byte_data(client, reg, value);
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* Set the period for DIM status
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* @client: the i2c client
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* @dim: either LP3944_DIM0 or LP3944_DIM1
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* @period: period of a blink, that is a on/off cycle, expressed in ms.
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static int lp3944_dim_set_period(struct i2c_client *client, u8 dim, u16 period)
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if (dim == LP3944_DIM0)
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psc_reg = LP3944_REG_PSC0;
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else if (dim == LP3944_DIM1)
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psc_reg = LP3944_REG_PSC1;
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/* Convert period to Prescaler value */
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if (period > LP3944_PERIOD_MAX)
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psc_value = (period * 255) / LP3944_PERIOD_MAX;
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err = lp3944_reg_write(client, psc_reg, psc_value);
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* Set the duty cycle for DIM status
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* @client: the i2c client
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* @dim: either LP3944_DIM0 or LP3944_DIM1
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* @duty_cycle: percentage of a period during which a led is ON
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static int lp3944_dim_set_dutycycle(struct i2c_client *client, u8 dim,
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if (dim == LP3944_DIM0)
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pwm_reg = LP3944_REG_PWM0;
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else if (dim == LP3944_DIM1)
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pwm_reg = LP3944_REG_PWM1;
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/* Convert duty cycle to PWM value */
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if (duty_cycle > LP3944_DUTY_CYCLE_MAX)
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pwm_value = (duty_cycle * 255) / LP3944_DUTY_CYCLE_MAX;
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err = lp3944_reg_write(client, pwm_reg, pwm_value);
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* @led: a lp3944_led_data structure
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* @status: one of LP3944_LED_STATUS_OFF
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* LP3944_LED_STATUS_ON
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* LP3944_LED_STATUS_DIM0
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* LP3944_LED_STATUS_DIM1
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static int lp3944_led_set(struct lp3944_led_data *led, u8 status)
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struct lp3944_data *data = i2c_get_clientdata(led->client);
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dev_dbg(&led->client->dev, "%s: %s, status before normalization:%d\n",
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__func__, led->ldev.name, status);
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reg = LP3944_REG_LS0;
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reg = LP3944_REG_LS1;
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if (status > LP3944_LED_STATUS_DIM1)
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/* invert only 0 and 1, leave unchanged the other values,
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* remember we are abusing status to set blink patterns
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if (led->type == LP3944_LED_TYPE_LED_INVERTED && status < 2)
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mutex_lock(&data->lock);
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lp3944_reg_read(led->client, reg, &val);
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val &= ~(LP3944_LED_STATUS_MASK << (id << 1));
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val |= (status << (id << 1));
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dev_dbg(&led->client->dev, "%s: %s, reg:%d id:%d status:%d val:%#x\n",
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__func__, led->ldev.name, reg, id, status, val);
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err = lp3944_reg_write(led->client, reg, val);
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mutex_unlock(&data->lock);
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static int lp3944_led_set_blink(struct led_classdev *led_cdev,
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unsigned long *delay_on,
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unsigned long *delay_off)
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struct lp3944_led_data *led = ldev_to_led(led_cdev);
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/* units are in ms */
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if (*delay_on + *delay_off > LP3944_PERIOD_MAX)
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if (*delay_on == 0 && *delay_off == 0) {
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/* Special case: the leds subsystem requires a default user
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* friendly blink pattern for the LED. Let's blink the led
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period = (*delay_on) + (*delay_off);
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/* duty_cycle is the percentage of period during which the led is ON */
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duty_cycle = 100 * (*delay_on) / period;
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/* invert duty cycle for inverted leds, this has the same effect of
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* swapping delay_on and delay_off
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if (led->type == LP3944_LED_TYPE_LED_INVERTED)
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duty_cycle = 100 - duty_cycle;
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/* NOTE: using always the first DIM mode, this means that all leds
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* will have the same blinking pattern.
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* We could find a way later to have two leds blinking in hardware
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* with different patterns at the same time, falling back to software
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* control for the other ones.
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err = lp3944_dim_set_period(led->client, LP3944_DIM0, period);
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err = lp3944_dim_set_dutycycle(led->client, LP3944_DIM0, duty_cycle);
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dev_dbg(&led->client->dev, "%s: OK hardware accelerated blink!\n",
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led->status = LP3944_LED_STATUS_DIM0;
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schedule_work(&led->work);
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static void lp3944_led_set_brightness(struct led_classdev *led_cdev,
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enum led_brightness brightness)
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struct lp3944_led_data *led = ldev_to_led(led_cdev);
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dev_dbg(&led->client->dev, "%s: %s, %d\n",
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__func__, led_cdev->name, brightness);
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led->status = brightness;
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schedule_work(&led->work);
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static void lp3944_led_work(struct work_struct *work)
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struct lp3944_led_data *led;
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led = container_of(work, struct lp3944_led_data, work);
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lp3944_led_set(led, led->status);
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static int lp3944_configure(struct i2c_client *client,
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struct lp3944_data *data,
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struct lp3944_platform_data *pdata)
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for (i = 0; i < pdata->leds_size; i++) {
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struct lp3944_led *pled = &pdata->leds[i];
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struct lp3944_led_data *led = &data->leds[i];
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led->client = client;
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switch (pled->type) {
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case LP3944_LED_TYPE_LED:
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case LP3944_LED_TYPE_LED_INVERTED:
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led->type = pled->type;
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led->status = pled->status;
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led->ldev.name = pled->name;
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led->ldev.max_brightness = 1;
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led->ldev.brightness_set = lp3944_led_set_brightness;
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led->ldev.blink_set = lp3944_led_set_blink;
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led->ldev.flags = LED_CORE_SUSPENDRESUME;
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INIT_WORK(&led->work, lp3944_led_work);
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err = led_classdev_register(&client->dev, &led->ldev);
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dev_err(&client->dev,
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"couldn't register LED %s\n",
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/* to expose the default value to userspace */
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led->ldev.brightness = led->status;
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/* Set the default led status */
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err = lp3944_led_set(led, led->status);
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dev_err(&client->dev,
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"%s couldn't set STATUS %d\n",
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led->ldev.name, led->status);
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case LP3944_LED_TYPE_NONE:
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for (i = i - 1; i >= 0; i--)
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switch (pdata->leds[i].type) {
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case LP3944_LED_TYPE_LED:
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case LP3944_LED_TYPE_LED_INVERTED:
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led_classdev_unregister(&data->leds[i].ldev);
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cancel_work_sync(&data->leds[i].work);
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case LP3944_LED_TYPE_NONE:
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static int __devinit lp3944_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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struct lp3944_platform_data *lp3944_pdata = client->dev.platform_data;
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struct lp3944_data *data;
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if (lp3944_pdata == NULL) {
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dev_err(&client->dev, "no platform data\n");
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/* Let's see whether this adapter can support what we need. */
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if (!i2c_check_functionality(client->adapter,
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I2C_FUNC_SMBUS_BYTE_DATA)) {
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dev_err(&client->dev, "insufficient functionality!\n");
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data = kzalloc(sizeof(struct lp3944_data), GFP_KERNEL);
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data->client = client;
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i2c_set_clientdata(client, data);
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mutex_init(&data->lock);
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err = lp3944_configure(client, data, lp3944_pdata);
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dev_info(&client->dev, "lp3944 enabled\n");
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static int __devexit lp3944_remove(struct i2c_client *client)
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struct lp3944_platform_data *pdata = client->dev.platform_data;
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struct lp3944_data *data = i2c_get_clientdata(client);
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for (i = 0; i < pdata->leds_size; i++)
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switch (data->leds[i].type) {
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case LP3944_LED_TYPE_LED:
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case LP3944_LED_TYPE_LED_INVERTED:
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led_classdev_unregister(&data->leds[i].ldev);
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cancel_work_sync(&data->leds[i].work);
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case LP3944_LED_TYPE_NONE:
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/* lp3944 i2c driver struct */
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static const struct i2c_device_id lp3944_id[] = {
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MODULE_DEVICE_TABLE(i2c, lp3944_id);
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static struct i2c_driver lp3944_driver = {
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.probe = lp3944_probe,
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.remove = __devexit_p(lp3944_remove),
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.id_table = lp3944_id,
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static int __init lp3944_module_init(void)
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return i2c_add_driver(&lp3944_driver);
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static void __exit lp3944_module_exit(void)
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i2c_del_driver(&lp3944_driver);
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module_init(lp3944_module_init);
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module_exit(lp3944_module_exit);
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MODULE_AUTHOR("Antonio Ospite <ospite@studenti.unina.it>");
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MODULE_DESCRIPTION("LP3944 Fun Light Chip");
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MODULE_LICENSE("GPL");