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// SPDX-License-Identifier: GPL-2.0+
//
// Gateworks I2C PLD GPIO expander
//
// Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
//
// Based on code and know-how from the OpenWrt driver:
// Copyright (C) 2009 Gateworks Corporation
// Authors: Chris Lang, Imre Kaloz
#include <linux/bits.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/gpio/driver.h>
#include <linux/i2c.h>
#include <linux/module.h>
/**
* struct gw_pld - State container for Gateworks PLD
* @chip: GPIO chip instance
* @client: I2C client
* @out: shadow register for the output bute
*/
struct gw_pld {
struct gpio_chip chip;
struct i2c_client *client;
u8 out;
};
/*
* The Gateworks I2C PLD chip only expose one read and one write register.
* Writing a "one" bit (to match the reset state) lets that pin be used as an
* input. It is an open-drain model.
*/
static int gw_pld_input8(struct gpio_chip *gc, unsigned offset)
{
struct gw_pld *gw = gpiochip_get_data(gc);
gw->out |= BIT(offset);
return i2c_smbus_write_byte(gw->client, gw->out);
}
static int gw_pld_get8(struct gpio_chip *gc, unsigned offset)
{
struct gw_pld *gw = gpiochip_get_data(gc);
s32 val;
val = i2c_smbus_read_byte(gw->client);
return (val < 0) ? 0 : !!(val & BIT(offset));
}
static int gw_pld_output8(struct gpio_chip *gc, unsigned offset, int value)
{
struct gw_pld *gw = gpiochip_get_data(gc);
if (value)
gw->out |= BIT(offset);
else
gw->out &= ~BIT(offset);
return i2c_smbus_write_byte(gw->client, gw->out);
}
static void gw_pld_set8(struct gpio_chip *gc, unsigned offset, int value)
{
gw_pld_output8(gc, offset, value);
}
static int gw_pld_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct device *dev = &client->dev;
struct device_node *np = dev->of_node;
struct gw_pld *gw;
int ret;
gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL);
if (!gw)
return -ENOMEM;
gw->chip.base = -1;
gw->chip.can_sleep = true;
gw->chip.parent = dev;
gw->chip.of_node = np;
gw->chip.owner = THIS_MODULE;
gw->chip.label = dev_name(dev);
gw->chip.ngpio = 8;
gw->chip.direction_input = gw_pld_input8;
gw->chip.get = gw_pld_get8;
gw->chip.direction_output = gw_pld_output8;
gw->chip.set = gw_pld_set8;
gw->client = client;
/*
* The Gateworks I2C PLD chip does not properly send the acknowledge
* bit at all times, but we can still use the standard i2c_smbus
* functions by simply ignoring this bit.
*/
client->flags |= I2C_M_IGNORE_NAK;
gw->out = 0xFF;
i2c_set_clientdata(client, gw);
ret = devm_gpiochip_add_data(dev, &gw->chip, gw);
if (ret)
return ret;
dev_info(dev, "registered Gateworks PLD GPIO device\n");
return 0;
}
static const struct i2c_device_id gw_pld_id[] = {
{ "gw-pld", },
{ }
};
MODULE_DEVICE_TABLE(i2c, gw_pld_id);
static const struct of_device_id gw_pld_dt_ids[] = {
{ .compatible = "gateworks,pld-gpio", },
{ },
};
MODULE_DEVICE_TABLE(of, gw_pld_dt_ids);
static struct i2c_driver gw_pld_driver = {
.driver = {
.name = "gw_pld",
.of_match_table = gw_pld_dt_ids,
},
.probe = gw_pld_probe,
.id_table = gw_pld_id,
};
module_i2c_driver(gw_pld_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
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