w1: Add support for DS28EA00 sequence to w1-therm

This patch provides support for the DS28EA00 digital thermometer.

The DS28EA00 provides an additional two pins for implementing a sequence
detection algorithm.  This feature allows you to determine the physical
location of the chip in the 1-wire bus without needing pre-existing
knowledge of the bus ordering.  Support is provided through the sysfs
w1_seq file.  The file will contain a single line with an integer value
representing the device index in the bus starting at 0.

Signed-off-by: Matt Campbell <mattrcampbell@gmail.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/stable/sysfs-driver-w1_ds28ea00

@@ -0,0 +1,6 @@
+What:		/sys/bus/w1/devices/.../w1_seq
+Date:		Apr 2015
+Contact:	Matt Campbell <mattrcampbell@gmail.com>
+Description:	Support for the DS28EA00 chain sequence function
+		see Documentation/w1/slaves/w1_therm for detailed information
+Users:		any user space application which wants to communicate with DS28EA00

Documentation/w1/slaves/w1_therm

@@ -11,12 +11,14 @@ Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
 Description
 -----------
 
-w1_therm provides basic temperature conversion for ds18*20 devices.
+w1_therm provides basic temperature conversion for ds18*20 devices, and the
+ds28ea00 device.
 supported family codes:
 W1_THERM_DS18S20	0x10
 W1_THERM_DS1822		0x22
 W1_THERM_DS18B20	0x28
 W1_THERM_DS1825		0x3B
+W1_THERM_DS28EA00	0x42
 
 Support is provided through the sysfs w1_slave file.  Each open and
 read sequence will initiate a temperature conversion then provide two
@@ -48,3 +50,10 @@ resistor).  The DS18b20 temperature sensor specification lists a
 maximum current draw of 1.5mA and that a 5k pullup resistor is not
 sufficient.  The strong pullup is designed to provide the additional
 current required.
+
+The DS28EA00 provides an additional two pins for implementing a sequence
+detection algorithm.  This feature allows you to determine the physical
+location of the chip in the 1-wire bus without needing pre-existing
+knowledge of the bus ordering.  Support is provided through the sysfs
+w1_seq file.  The file will contain a single line with an integer value
+representing the device index in the bus starting at 0.

drivers/w1/slaves/w1_therm.c

@@ -92,20 +92,37 @@ static void w1_therm_remove_slave(struct w1_slave *sl)
 static ssize_t w1_slave_show(struct device *device,
 	struct device_attribute *attr, char *buf);
 
+static ssize_t w1_seq_show(struct device *device,
+	struct device_attribute *attr, char *buf);
+
 static DEVICE_ATTR_RO(w1_slave);
+static DEVICE_ATTR_RO(w1_seq);
 
 static struct attribute *w1_therm_attrs[] = {
 	&dev_attr_w1_slave.attr,
 	NULL,
 };
+
+static struct attribute *w1_ds28ea00_attrs[] = {
+	&dev_attr_w1_slave.attr,
+	&dev_attr_w1_seq.attr,
+	NULL,
+};
 ATTRIBUTE_GROUPS(w1_therm);
+ATTRIBUTE_GROUPS(w1_ds28ea00);
 
 static struct w1_family_ops w1_therm_fops = {
 	.add_slave	= w1_therm_add_slave,
 	.remove_slave	= w1_therm_remove_slave,
 	.groups		= w1_therm_groups,
 };
 
+static struct w1_family_ops w1_ds28ea00_fops = {
+	.add_slave	= w1_therm_add_slave,
+	.remove_slave	= w1_therm_remove_slave,
+	.groups		= w1_ds28ea00_groups,
+};
+
 static struct w1_family w1_therm_family_DS18S20 = {
 	.fid = W1_THERM_DS18S20,
 	.fops = &w1_therm_fops,
@@ -123,7 +140,7 @@ static struct w1_family w1_therm_family_DS1822 = {
 
 static struct w1_family w1_therm_family_DS28EA00 = {
 	.fid = W1_THERM_DS28EA00,
-	.fops = &w1_therm_fops,
+	.fops = &w1_ds28ea00_fops,
 };
 
 static struct w1_family w1_therm_family_DS1825 = {
@@ -316,6 +333,89 @@ static ssize_t w1_slave_show(struct device *device,
 	return ret;
 }
 
+#define W1_42_CHAIN	0x99
+#define W1_42_CHAIN_OFF	0x3C
+#define W1_42_CHAIN_OFF_INV	0xC3
+#define W1_42_CHAIN_ON	0x5A
+#define W1_42_CHAIN_ON_INV	0xA5
+#define W1_42_CHAIN_DONE 0x96
+#define W1_42_CHAIN_DONE_INV 0x69
+#define W1_42_COND_READ	0x0F
+#define W1_42_SUCCESS_CONFIRM_BYTE 0xAA
+#define W1_42_FINISHED_BYTE 0xFF
+static ssize_t w1_seq_show(struct device *device,
+	struct device_attribute *attr, char *buf)
+{
+	struct w1_slave *sl = dev_to_w1_slave(device);
+	ssize_t c = PAGE_SIZE;
+	int rv;
+	int i;
+	u8 ack;
+	u64 rn;
+	struct w1_reg_num *reg_num;
+	int seq = 0;
+
+	mutex_lock(&sl->master->mutex);
+	/* Place all devices in CHAIN state */
+	if (w1_reset_bus(sl->master))
+		goto error;
+	w1_write_8(sl->master, W1_SKIP_ROM);
+	w1_write_8(sl->master, W1_42_CHAIN);
+	w1_write_8(sl->master, W1_42_CHAIN_ON);
+	w1_write_8(sl->master, W1_42_CHAIN_ON_INV);
+	msleep(sl->master->pullup_duration);
+
+	/* check for acknowledgment */
+	ack = w1_read_8(sl->master);
+	if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
+		goto error;
+
+	/* In case the bus fails to send 0xFF, limit*/
+	for (i = 0; i <= 64; i++) {
+		if (w1_reset_bus(sl->master))
+			goto error;
+
+		w1_write_8(sl->master, W1_42_COND_READ);
+		rv = w1_read_block(sl->master, (u8 *)&rn, 8);
+		reg_num = (struct w1_reg_num *) &rn;
+		if ((char)reg_num->family == W1_42_FINISHED_BYTE)
+			break;
+		if (sl->reg_num.id == reg_num->id)
+			seq = i;
+
+		w1_write_8(sl->master, W1_42_CHAIN);
+		w1_write_8(sl->master, W1_42_CHAIN_DONE);
+		w1_write_8(sl->master, W1_42_CHAIN_DONE_INV);
+		w1_read_block(sl->master, &ack, sizeof(ack));
+
+		/* check for acknowledgment */
+		ack = w1_read_8(sl->master);
+		if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
+			goto error;
+
+	}
+
+	/* Exit from CHAIN state */
+	if (w1_reset_bus(sl->master))
+		goto error;
+	w1_write_8(sl->master, W1_SKIP_ROM);
+	w1_write_8(sl->master, W1_42_CHAIN);
+	w1_write_8(sl->master, W1_42_CHAIN_OFF);
+	w1_write_8(sl->master, W1_42_CHAIN_OFF_INV);
+
+	/* check for acknowledgment */
+	ack = w1_read_8(sl->master);
+	if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
+		goto error;
+	mutex_unlock(&sl->master->mutex);
+
+	c -= snprintf(buf + PAGE_SIZE - c, c, "%d\n", seq);
+	return PAGE_SIZE - c;
+error:
+	mutex_unlock(&sl->master->bus_mutex);
+	return -EIO;
+}
+
 static int __init w1_therm_init(void)
 {
 	int err, i;