[PATCH v3] w1: introduce an ability to specify microseconds bus scanning intervals

From: Dmitry Khromov
Date: Thu Apr 23 2015 - 07:41:00 EST

Some of 1-Wire devices commonly associated with physical access control
systems are attached/generate presence for as short as 100 ms - hence
the tens-to-hundreds milliseconds scan intervals are required.

Signed-off-by: Dmitry Khromov <dk@xxxxxxxxxxxx>
---
Documentation/ABI/stable/sysfs-bus-w1 | 11 +++++++++++
Documentation/w1/w1.generic | 30 +++++++++++++++++++-----------
drivers/w1/w1.c | 17 ++++++++++++++++-
3 files changed, 46 insertions(+), 12 deletions(-)
create mode 100644 Documentation/ABI/stable/sysfs-bus-w1

diff --git a/Documentation/ABI/stable/sysfs-bus-w1 b/Documentation/ABI/stable/sysfs-bus-w1
new file mode 100644
index 0000000..140d85b
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-bus-w1
@@ -0,0 +1,11 @@
+What: /sys/bus/w1/devices/.../w1_master_timeout_us
+Date: April 2015
+Contact: Dmitry Khromov <dk@xxxxxxxxxxxx>
+Description: Bus scanning interval, microseconds component.
+ Some of 1-Wire devices commonly associated with physical access
+ control systems are attached/generate presence for as short as
+ 100 ms - hence the tens-to-hundreds milliseconds scan intervals
+ are required.
+ see Documentation/w1/w1.generic for detailed information.
+Users: any user space application which wants to know bus scanning
+ interval
diff --git a/Documentation/w1/w1.generic b/Documentation/w1/w1.generic
index b2033c6..b3ffaf8 100644
--- a/Documentation/w1/w1.generic
+++ b/Documentation/w1/w1.generic
@@ -76,21 +76,24 @@ See struct w1_bus_master definition in w1.h for details.

w1 master sysfs interface
------------------------------------------------------------------
-<xx-xxxxxxxxxxxxx> - a directory for a found device. The format is family-serial
+<xx-xxxxxxxxxxxxx> - A directory for a found device. The format is family-serial
bus - (standard) symlink to the w1 bus
driver - (standard) symlink to the w1 driver
-w1_master_add - Manually register a slave device
-w1_master_attempts - the number of times a search was attempted
+w1_master_add - (rw) manually register a slave device
+w1_master_attempts - (ro) the number of times a search was attempted
w1_master_max_slave_count
- - maximum number of slaves to search for at a time
-w1_master_name - the name of the device (w1_bus_masterX)
-w1_master_pullup - 5V strong pullup 0 enabled, 1 disabled
-w1_master_remove - Manually remove a slave device
-w1_master_search - the number of searches left to do, -1=continual (default)
+ - (rw) maximum number of slaves to search for at a time
+w1_master_name - (ro) the name of the device (w1_bus_masterX)
+w1_master_pullup - (rw) 5V strong pullup 0 enabled, 1 disabled
+w1_master_remove - (rw) manually remove a slave device
+w1_master_search - (rw) the number of searches left to do,
+ -1=continual (default)
w1_master_slave_count
- - the number of slaves found
-w1_master_slaves - the names of the slaves, one per line
-w1_master_timeout - the delay in seconds between searches
+ - (ro) the number of slaves found
+w1_master_slaves - (ro) the names of the slaves, one per line
+w1_master_timeout - (ro) the delay in seconds between searches
+w1_master_timeout_us
+ - (ro) the delay in microseconds beetwen searches

If you have a w1 bus that never changes (you don't add or remove devices),
you can set the module parameter search_count to a small positive number
@@ -101,6 +104,11 @@ generally only make sense when searching is disabled, as a search will
redetect manually removed devices that are present and timeout manually
added devices that aren't on the bus.

+Bus searches occur at an interval, specified as a summ of timeout and
+timeout_us module parameters (either of which may be 0) for as long as
+w1_master_search remains greater than 0 or is -1. Each search attempt
+decrements w1_master_search by 1 (down to 0) and increments
+w1_master_attempts by 1.

w1 slave sysfs interface
------------------------------------------------------------------
diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index 181f41c..c9a7ff6 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <zbr@xxxxxxxxxxx>");
MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol.");

static int w1_timeout = 10;
+static int w1_timeout_us = 0;
int w1_max_slave_count = 64;
int w1_max_slave_ttl = 10;

module_param_named(timeout, w1_timeout, int, 0);
MODULE_PARM_DESC(timeout, "time in seconds between automatic slave searches");
+module_param_named(timeout_us, w1_timeout_us, int, 0);
+MODULE_PARM_DESC(timeout, "time in microseconds between automatic slave"
+ " searches");
/* A search stops when w1_max_slave_count devices have been found in that
* search. The next search will start over and detect the same set of devices
* on a static 1-wire bus. Memory is not allocated based on this number, just
@@ -317,6 +321,14 @@ static ssize_t w1_master_attribute_show_timeout(struct device *dev, struct devic
return count;
}

+static ssize_t w1_master_attribute_show_timeout_us(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ ssize_t count;
+ count = sprintf(buf, "%d\n", w1_timeout_us);
+ return count;
+}
+
static ssize_t w1_master_attribute_store_max_slave_count(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
@@ -543,6 +555,7 @@ static W1_MASTER_ATTR_RO(slave_count, S_IRUGO);
static W1_MASTER_ATTR_RW(max_slave_count, S_IRUGO | S_IWUSR | S_IWGRP);
static W1_MASTER_ATTR_RO(attempts, S_IRUGO);
static W1_MASTER_ATTR_RO(timeout, S_IRUGO);
+static W1_MASTER_ATTR_RO(timeout_us, S_IRUGO);
static W1_MASTER_ATTR_RO(pointer, S_IRUGO);
static W1_MASTER_ATTR_RW(search, S_IRUGO | S_IWUSR | S_IWGRP);
static W1_MASTER_ATTR_RW(pullup, S_IRUGO | S_IWUSR | S_IWGRP);
@@ -556,6 +569,7 @@ static struct attribute *w1_master_default_attrs[] = {
&w1_master_attribute_max_slave_count.attr,
&w1_master_attribute_attempts.attr,
&w1_master_attribute_timeout.attr,
+ &w1_master_attribute_timeout_us.attr,
&w1_master_attribute_pointer.attr,
&w1_master_attribute_search.attr,
&w1_master_attribute_pullup.attr,
@@ -1108,7 +1122,8 @@ int w1_process(void *data)
/* As long as w1_timeout is only set by a module parameter the sleep
* time can be calculated in jiffies once.
*/
- const unsigned long jtime = msecs_to_jiffies(w1_timeout * 1000);
+ const unsigned long jtime =
+ usecs_to_jiffies(w1_timeout * 1000000 + w1_timeout_us);
/* remainder if it woke up early */
unsigned long jremain = 0;

--
2.3.5

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