Add bitbanging pullups, use them for w1-gpio

Allows parasite power to work, uses module option pullup=1

drivers/w1/masters/w1-gpio.c

@@ -18,6 +18,9 @@
 #include "../w1.h"
 #include "../w1_int.h"
 
+static int w1_gpio_pullup = 0;
+module_param_named(pullup, w1_gpio_pullup, int, 0);
+
 static void w1_gpio_write_bit_dir(void *data, u8 bit)
 {
 	struct w1_gpio_platform_data *pdata = data;
@@ -42,6 +45,16 @@ static u8 w1_gpio_read_bit(void *data)
 	return gpio_get_value(pdata->pin) ? 1 : 0;
 }
 
+static void w1_gpio_bitbang_pullup(void *data, u8 on)
+{
+	struct w1_gpio_platform_data *pdata = data;
+
+	if (on)
+		gpio_direction_output(pdata->pin, 1);
+	else
+		gpio_direction_input(pdata->pin);
+}
+
 static int __init w1_gpio_probe(struct platform_device *pdev)
 {
 	struct w1_bus_master *master;
@@ -70,6 +83,13 @@ static int __init w1_gpio_probe(struct platform_device *pdev)
 		master->write_bit = w1_gpio_write_bit_dir;
 	}
 
+	if (w1_gpio_pullup)
+		if (pdata->is_open_drain)
+			printk(KERN_ERR "w1-gpio 'pullup' option "
+				"doesn't work with open drain GPIO\n");
+		else
+			master->bitbang_pullup = w1_gpio_bitbang_pullup;
+
 	err = w1_add_master_device(master);
 	if (err)
 		goto free_gpio;

drivers/w1/w1.h

@@ -148,6 +148,12 @@ struct w1_bus_master
 	 */
 	u8		(*set_pullup)(void *, int);
 
+	/**
+	 * Turns the pullup on/off in bitbanging mode, takes an on/off argument.
+	 * @return -1=Error, 0=completed
+	 */
+	void	(*bitbang_pullup)(void *, u8);
+
 	/** Really nice hardware can handles the different types of ROM search
 	 *  w1_master* is passed to the slave found callback.
 	 */

drivers/w1/w1_int.c

@@ -110,26 +110,29 @@ int w1_add_master_device(struct w1_bus_master *master)
 	struct w1_netlink_msg msg;
 	int id, found;
 
-        /* validate minimum functionality */
-        if (!(master->touch_bit && master->reset_bus) &&
-            !(master->write_bit && master->read_bit) &&
+	/* validate minimum functionality */
+	if (!(master->touch_bit && master->reset_bus) &&
+	    !(master->write_bit && master->read_bit) &&
 	    !(master->write_byte && master->read_byte && master->reset_bus)) {
 		printk(KERN_ERR "w1_add_master_device: invalid function set\n");
 		return(-EINVAL);
-        }
-	/* While it would be electrically possible to make a device that
-	 * generated a strong pullup in bit bang mode, only hardware that
-	 * controls 1-wire time frames are even expected to support a strong
-	 * pullup.  w1_io.c would need to support calling set_pullup before
-	 * the last write_bit operation of a w1_write_8 which it currently
-	 * doesn't.
-	 */
+	}
+
+	/* bitbanging hardware uses bitbang_pullup, other hardware uses set_pullup
+	 * and takes care of timing itself */
 	if (!master->write_byte && !master->touch_bit && master->set_pullup) {
 		printk(KERN_ERR "w1_add_master_device: set_pullup requires "
 			"write_byte or touch_bit, disabling\n");
 		master->set_pullup = NULL;
 	}
 
+	if (master->set_pullup && master->bitbang_pullup)
+	{
+		printk(KERN_ERR "w1_add_master_device: set_pullup should not "
+			"be set when bitbang_pullup is used, disabling\n");
+		master->set_pullup = NULL;
+	}
+
 	/* Lock until the device is added (or not) to w1_masters. */
 	mutex_lock(&w1_mlock);
 	/* Search for the first available id (starting at 1). */

drivers/w1/w1_io.c

@@ -127,10 +127,18 @@ static void w1_pre_write(struct w1_master *dev)
 static void w1_post_write(struct w1_master *dev)
 {
 	if (dev->pullup_duration) {
-		if (dev->enable_pullup && dev->bus_master->set_pullup)
-			dev->bus_master->set_pullup(dev->bus_master->data, 0);
-		else
+		if (dev->enable_pullup) {
+			if (dev->bus_master->set_pullup) {
+				dev->bus_master->set_pullup(dev->bus_master->data, 0);
+			} else if (dev->bus_master->bitbang_pullup) {
+				dev->bus_master->bitbang_pullup(dev->bus_master->data, 1);
+				msleep(dev->pullup_duration);
+				dev->bus_master->bitbang_pullup(dev->bus_master->data, 0);
+			}
+        } else {
 			msleep(dev->pullup_duration);
+        }
+
 		dev->pullup_duration = 0;
 	}
 }