w1-gpio: add GPIO w1 bus master driver

Add a GPIO 1-wire bus master driver.  The driver used the GPIO API to
control the wire and the GPIO pin can be specified using platform data
similar to i2c-gpio.  The driver was tested with AT91SAM9260 + DS2401.

Signed-off-by: Ville Syrjala <syrjala@sci.fi>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/w1/masters/w1-gpio.c

@@ -0,0 +1,124 @@
+/*
+ * w1-gpio - GPIO w1 bus master driver
+ *
+ * Copyright (C) 2007 Ville Syrjala <syrjala@sci.fi>
+ *
+ * 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/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/w1-gpio.h>
+
+#include "../w1.h"
+#include "../w1_int.h"
+
+#include <asm/gpio.h>
+
+static void w1_gpio_write_bit_dir(void *data, u8 bit)
+{
+	struct w1_gpio_platform_data *pdata = data;
+
+	if (bit)
+		gpio_direction_input(pdata->pin);
+	else
+		gpio_direction_output(pdata->pin, 0);
+}
+
+static void w1_gpio_write_bit_val(void *data, u8 bit)
+{
+	struct w1_gpio_platform_data *pdata = data;
+
+	gpio_set_value(pdata->pin, bit);
+}
+
+static u8 w1_gpio_read_bit(void *data)
+{
+	struct w1_gpio_platform_data *pdata = data;
+
+	return gpio_get_value(pdata->pin);
+}
+
+static int __init w1_gpio_probe(struct platform_device *pdev)
+{
+	struct w1_bus_master *master;
+	struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
+	int err;
+
+	if (!pdata)
+		return -ENXIO;
+
+	master = kzalloc(sizeof(struct w1_bus_master), GFP_KERNEL);
+	if (!master)
+		return -ENOMEM;
+
+	err = gpio_request(pdata->pin, "w1");
+	if (err)
+		goto free_master;
+
+	master->data = pdata;
+	master->read_bit = w1_gpio_read_bit;
+
+	if (pdata->is_open_drain) {
+		gpio_direction_output(pdata->pin, 1);
+		master->write_bit = w1_gpio_write_bit_val;
+	} else {
+		gpio_direction_input(pdata->pin);
+		master->write_bit = w1_gpio_write_bit_dir;
+	}
+
+	err = w1_add_master_device(master);
+	if (err)
+		goto free_gpio;
+
+	platform_set_drvdata(pdev, master);
+
+	return 0;
+
+ free_gpio:
+	gpio_free(pdata->pin);
+ free_master:
+	kfree(master);
+
+	return err;
+}
+
+static int __exit w1_gpio_remove(struct platform_device *pdev)
+{
+	struct w1_bus_master *master = platform_get_drvdata(pdev);
+	struct w1_gpio_platform_data *pdata = pdev->dev.platform_data;
+
+	w1_remove_master_device(master);
+	gpio_free(pdata->pin);
+	kfree(master);
+
+	return 0;
+}
+
+static struct platform_driver w1_gpio_driver = {
+	.driver = {
+		.name	= "w1-gpio",
+		.owner	= THIS_MODULE,
+	},
+	.remove	= __exit_p(w1_gpio_remove),
+};
+
+static int __init w1_gpio_init(void)
+{
+	return platform_driver_probe(&w1_gpio_driver, w1_gpio_probe);
+}
+
+static void __exit w1_gpio_exit(void)
+{
+	platform_driver_unregister(&w1_gpio_driver);
+}
+
+module_init(w1_gpio_init);
+module_exit(w1_gpio_exit);
+
+MODULE_DESCRIPTION("GPIO w1 bus master driver");
+MODULE_AUTHOR("Ville Syrjala <syrjala@sci.fi>");
+MODULE_LICENSE("GPL");