3 files changed, 117 insertions, 2 deletions

diff --git a/Documentation/ABI/stable/sysfs-driver-w1_ds28ea00 b/Documentation/ABI/stable/sysfs-driver-w1_ds28ea00
new file mode 100644
index 000000000000..e928def14f28
--- /dev/null
+++ b/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
diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm
index cc62a95e4776..13411fe52f7f 100644
--- a/Documentation/w1/slaves/w1_therm
+++ b/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.
diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index 55eb86c9e214..d21e6864b06f 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -92,13 +92,24 @@ 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,
@@ -106,6 +117,12 @@ static struct w1_family_ops w1_therm_fops = {
         .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 @@ post_unlock:
         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;