292 lines
7.0 KiB
C
292 lines
7.0 KiB
C
/*
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* Bitbanging I2C bus driver using the GPIO API
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*
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* Copyright (C) 2007 Atmel Corporation
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*
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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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*/
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#include <linux/i2c.h>
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#include <linux/i2c-algo-bit.h>
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#include <linux/i2c-gpio.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/platform_device.h>
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#include <linux/gpio.h>
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#include <linux/of.h>
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#include <linux/of_gpio.h>
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struct i2c_gpio_private_data {
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struct i2c_adapter adap;
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struct i2c_algo_bit_data bit_data;
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struct i2c_gpio_platform_data pdata;
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};
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/* Toggle SDA by changing the direction of the pin */
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static void i2c_gpio_setsda_dir(void *data, int state)
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{
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struct i2c_gpio_platform_data *pdata = data;
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if (state)
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gpio_direction_input(pdata->sda_pin);
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else
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gpio_direction_output(pdata->sda_pin, 0);
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}
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/*
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* Toggle SDA by changing the output value of the pin. This is only
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* valid for pins configured as open drain (i.e. setting the value
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* high effectively turns off the output driver.)
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*/
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static void i2c_gpio_setsda_val(void *data, int state)
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{
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struct i2c_gpio_platform_data *pdata = data;
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gpio_set_value(pdata->sda_pin, state);
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}
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/* Toggle SCL by changing the direction of the pin. */
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static void i2c_gpio_setscl_dir(void *data, int state)
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{
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struct i2c_gpio_platform_data *pdata = data;
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if (state)
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gpio_direction_input(pdata->scl_pin);
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else
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gpio_direction_output(pdata->scl_pin, 0);
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}
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/*
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* Toggle SCL by changing the output value of the pin. This is used
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* for pins that are configured as open drain and for output-only
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* pins. The latter case will break the i2c protocol, but it will
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* often work in practice.
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*/
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static void i2c_gpio_setscl_val(void *data, int state)
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{
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struct i2c_gpio_platform_data *pdata = data;
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gpio_set_value(pdata->scl_pin, state);
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}
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static int i2c_gpio_getsda(void *data)
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{
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struct i2c_gpio_platform_data *pdata = data;
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return gpio_get_value(pdata->sda_pin);
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}
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static int i2c_gpio_getscl(void *data)
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{
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struct i2c_gpio_platform_data *pdata = data;
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return gpio_get_value(pdata->scl_pin);
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}
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static int of_i2c_gpio_get_pins(struct device_node *np,
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unsigned int *sda_pin, unsigned int *scl_pin)
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{
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if (of_gpio_count(np) < 2)
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return -ENODEV;
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*sda_pin = of_get_gpio(np, 0);
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*scl_pin = of_get_gpio(np, 1);
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if (*sda_pin == -EPROBE_DEFER || *scl_pin == -EPROBE_DEFER)
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return -EPROBE_DEFER;
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if (!gpio_is_valid(*sda_pin) || !gpio_is_valid(*scl_pin)) {
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pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
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np->full_name, *sda_pin, *scl_pin);
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return -ENODEV;
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}
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return 0;
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}
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static void of_i2c_gpio_get_props(struct device_node *np,
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struct i2c_gpio_platform_data *pdata)
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{
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u32 reg;
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of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
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if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", ®))
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pdata->timeout = msecs_to_jiffies(reg);
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pdata->sda_is_open_drain =
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of_property_read_bool(np, "i2c-gpio,sda-open-drain");
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pdata->scl_is_open_drain =
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of_property_read_bool(np, "i2c-gpio,scl-open-drain");
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pdata->scl_is_output_only =
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of_property_read_bool(np, "i2c-gpio,scl-output-only");
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}
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static int i2c_gpio_probe(struct platform_device *pdev)
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{
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struct i2c_gpio_private_data *priv;
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struct i2c_gpio_platform_data *pdata;
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struct i2c_algo_bit_data *bit_data;
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struct i2c_adapter *adap;
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unsigned int sda_pin, scl_pin;
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int ret;
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/* First get the GPIO pins; if it fails, we'll defer the probe. */
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if (pdev->dev.of_node) {
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ret = of_i2c_gpio_get_pins(pdev->dev.of_node,
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&sda_pin, &scl_pin);
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if (ret)
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return ret;
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} else {
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if (!dev_get_platdata(&pdev->dev))
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return -ENXIO;
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pdata = dev_get_platdata(&pdev->dev);
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sda_pin = pdata->sda_pin;
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scl_pin = pdata->scl_pin;
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}
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ret = devm_gpio_request(&pdev->dev, sda_pin, "sda");
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if (ret) {
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if (ret == -EINVAL)
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ret = -EPROBE_DEFER; /* Try again later */
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return ret;
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}
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ret = devm_gpio_request(&pdev->dev, scl_pin, "scl");
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if (ret) {
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if (ret == -EINVAL)
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ret = -EPROBE_DEFER; /* Try again later */
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return ret;
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}
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priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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adap = &priv->adap;
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bit_data = &priv->bit_data;
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pdata = &priv->pdata;
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if (pdev->dev.of_node) {
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pdata->sda_pin = sda_pin;
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pdata->scl_pin = scl_pin;
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of_i2c_gpio_get_props(pdev->dev.of_node, pdata);
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} else {
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memcpy(pdata, dev_get_platdata(&pdev->dev), sizeof(*pdata));
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}
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if (pdata->sda_is_open_drain) {
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gpio_direction_output(pdata->sda_pin, 1);
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bit_data->setsda = i2c_gpio_setsda_val;
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} else {
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gpio_direction_input(pdata->sda_pin);
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bit_data->setsda = i2c_gpio_setsda_dir;
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}
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if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
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gpio_direction_output(pdata->scl_pin, 1);
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bit_data->setscl = i2c_gpio_setscl_val;
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} else {
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gpio_direction_input(pdata->scl_pin);
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bit_data->setscl = i2c_gpio_setscl_dir;
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}
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if (!pdata->scl_is_output_only)
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bit_data->getscl = i2c_gpio_getscl;
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bit_data->getsda = i2c_gpio_getsda;
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if (pdata->udelay)
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bit_data->udelay = pdata->udelay;
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else if (pdata->scl_is_output_only)
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bit_data->udelay = 50; /* 10 kHz */
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else
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bit_data->udelay = 5; /* 100 kHz */
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if (pdata->timeout)
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bit_data->timeout = pdata->timeout;
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else
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bit_data->timeout = HZ / 10; /* 100 ms */
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bit_data->data = pdata;
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adap->owner = THIS_MODULE;
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if (pdev->dev.of_node)
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strlcpy(adap->name, dev_name(&pdev->dev), sizeof(adap->name));
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else
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snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
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adap->algo_data = bit_data;
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adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
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adap->dev.parent = &pdev->dev;
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adap->dev.of_node = pdev->dev.of_node;
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adap->nr = pdev->id;
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ret = i2c_bit_add_numbered_bus(adap);
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if (ret)
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return ret;
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platform_set_drvdata(pdev, priv);
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dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
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pdata->sda_pin, pdata->scl_pin,
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pdata->scl_is_output_only
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? ", no clock stretching" : "");
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return 0;
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}
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static int i2c_gpio_remove(struct platform_device *pdev)
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{
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struct i2c_gpio_private_data *priv;
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struct i2c_adapter *adap;
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priv = platform_get_drvdata(pdev);
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adap = &priv->adap;
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i2c_del_adapter(adap);
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return 0;
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}
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#if defined(CONFIG_OF)
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static const struct of_device_id i2c_gpio_dt_ids[] = {
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{ .compatible = "i2c-gpio", },
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{ /* sentinel */ }
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};
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MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
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#endif
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static struct platform_driver i2c_gpio_driver = {
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.driver = {
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.name = "i2c-gpio",
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.owner = THIS_MODULE,
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.of_match_table = of_match_ptr(i2c_gpio_dt_ids),
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},
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.probe = i2c_gpio_probe,
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.remove = i2c_gpio_remove,
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};
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static int __init i2c_gpio_init(void)
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{
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int ret;
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ret = platform_driver_register(&i2c_gpio_driver);
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if (ret)
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printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
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return ret;
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}
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subsys_initcall(i2c_gpio_init);
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static void __exit i2c_gpio_exit(void)
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{
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platform_driver_unregister(&i2c_gpio_driver);
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}
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module_exit(i2c_gpio_exit);
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MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
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MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("platform:i2c-gpio");
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