W1: feature, enable hardware strong pullup

Add a strong pullup option to the w1 system.  This supplies extra power
for parasite powered devices.  There is a w1_master_pullup sysfs entry and
enable_pullup module parameter to enable or disable the strong pullup.

The one wire bus requires at a minimum one wire and ground.  The common
wire is used for sending and receiving data as well as supplying power to
devices that are parasite powered of which temperature sensors can be one
example.  The bus must be idle and left high while a temperature
conversion is in progress, in addition the normal pullup resister on
larger networks or even higher temperatures might not supply enough power.
 The pullup resister can't provide too much pullup current, because
devices need to pull the bus down to write a value.  This enables the
strong pullup for supported hardware, which can supply more current when
requested.  Unsupported hardware will just delay with the bus high.

The hardware USB 2490 one wire bus master has a bit on some commands which
will enable the strong pullup as soon as the command finishes executing.
To use strong pullup, call the new w1_next_pullup function to register the
duration.  The next write command will call set_pullup before sending the
data, and reset the duration to zero once it returns.

Switched from simple_strtol to strict_strtol.

Signed-off-by: David Fries <david@fries.net>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 39 insertions, 1 deletions

diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index 9b5c11701c37..32418d4e555a 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -246,10 +246,14 @@ static ssize_t w1_master_attribute_store_search(struct device * dev,
                                                 struct device_attribute *attr,
                                                 const char * buf, size_t count)
 {
+        long tmp;
         struct w1_master *md = dev_to_w1_master(dev);
 
+        if (strict_strtol(buf, 0, &tmp) == -EINVAL)
+                return -EINVAL;
+
         mutex_lock(&md->mutex);
-        md->search_count = simple_strtol(buf, NULL, 0);
+        md->search_count = tmp;
         mutex_unlock(&md->mutex);
         wake_up_process(md->thread);
 
@@ -270,6 +274,38 @@ static ssize_t w1_master_attribute_show_search(struct device *dev,
         return count;
 }
 
+static ssize_t w1_master_attribute_store_pullup(struct device *dev,
+                                                struct device_attribute *attr,
+                                                const char *buf, size_t count)
+{
+        long tmp;
+        struct w1_master *md = dev_to_w1_master(dev);
+
+        if (strict_strtol(buf, 0, &tmp) == -EINVAL)
+                return -EINVAL;
+
+        mutex_lock(&md->mutex);
+        md->enable_pullup = tmp;
+        mutex_unlock(&md->mutex);
+        wake_up_process(md->thread);
+
+        return count;
+}
+
+static ssize_t w1_master_attribute_show_pullup(struct device *dev,
+                                               struct device_attribute *attr,
+                                               char *buf)
+{
+        struct w1_master *md = dev_to_w1_master(dev);
+        ssize_t count;
+
+        mutex_lock(&md->mutex);
+        count = sprintf(buf, "%d\n", md->enable_pullup);
+        mutex_unlock(&md->mutex);
+
+        return count;
+}
+
 static ssize_t w1_master_attribute_show_pointer(struct device *dev, struct device_attribute *attr, char *buf)
 {
         struct w1_master *md = dev_to_w1_master(dev);
@@ -365,6 +401,7 @@ static W1_MASTER_ATTR_RO(attempts, S_IRUGO);
 static W1_MASTER_ATTR_RO(timeout, S_IRUGO);
 static W1_MASTER_ATTR_RO(pointer, S_IRUGO);
 static W1_MASTER_ATTR_RW(search, S_IRUGO | S_IWUGO);
+static W1_MASTER_ATTR_RW(pullup, S_IRUGO | S_IWUGO);
 
 static struct attribute *w1_master_default_attrs[] = {
         &w1_master_attribute_name.attr,
@@ -375,6 +412,7 @@ static struct attribute *w1_master_default_attrs[] = {
         &w1_master_attribute_timeout.attr,
         &w1_master_attribute_pointer.attr,
         &w1_master_attribute_search.attr,
+        &w1_master_attribute_pullup.attr,
         NULL
 };