Introduce an ability to specify microseconds bus scanning intervals in w1 core

PATCH Superseded Dmitry Khromov 4 participants 10 messages Apr 14, 2015 – May 13, 2015 2 messages not in the archive

Subsystems (2)

Documentation W1 dallas's 1-wire bus

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Dmitry Khromov

author

2015-04-14 07:48 UTC #2 lore raw

PATCH 1/1 Introduce an ability to specify microseconds bus scanning intervals in w1 core

DS1990* "iButtons" and compatible RFID card readers commonly found at physical access control systems are usually attached/generate presence for as short as 100 ms - hence the tens-to-hundreds milliseconds scan intervals are required.

Tested on Raspberry Pi model B+ with DS2482-100 bus master, tens-of-milliseconds intervals are easily achieved without significant CPU load (and with unknown accuracy), and though I doubt microseconds-scale intervals are really feasible in terms of practical use and underlying buses timings, I believe it makes sense to give the ability of using them to those willing to try.

Signed-off-by Dmitry Khromov <[email protected]>

Acked-by Evgeniy Polyakov <[email protected]>

 drivers/w1/w1.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

---

drivers/w1/w1.c +16 -1

index 181f41c..73b4e2d 100644
@@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <[email protected]>");
 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;

Randy Dunlap

reviewer

2015-04-14 17:15 UTC #3 lore raw

Quoted 25 lines · Dmitry Khromov

DS1990* "iButtons" and compatible RFID card readers commonly found at physical access control systems are usually attached/generate presence for as short as 100 ms - hence the tens-to-hundreds milliseconds scan intervals are required.
Tested on Raspberry Pi model B+ with DS2482-100 bus master, tens-of-milliseconds intervals are easily achieved without significant CPU load (and with unknown accuracy), and though I doubt microseconds-scale intervals are really feasible in terms of practical use and underlying buses timings, I believe it makes sense to give the ability of using them to those willing to try.
Signed-off-by Dmitry Khromov <[email protected]>
Acked-by Evgeniy Polyakov <[email protected]>
 drivers/w1/w1.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)
---
drivers/w1/w1.c +0 -0
index 181f41c..73b4e2d 100644
@@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <[email protected]>");
 MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol.");
 

drivers/w1/w1.c MODULE_AUTHOR("Evgeniy Polyakov <[email protected]>"); · line 57

Quoted 10 lines

drivers/w1/w1.c +4 -0

 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");

The description string needs a space between "slave" and "searches".

Quoted 3 lines

drivers/w1/w1.c +0 -0

 /* 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

Signature · 1 line

~Randy

Dmitry Khromov

author

2015-04-22 22:02 UTC #4 lore raw

PATCH v2 1/1 w1: introduce an ability to specify microseconds bus scanning intervals

Signed-off-by Dmitry Khromov <[email protected]>

---
 drivers/w1/w1.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

drivers/w1/w1.c +16 -1

index 181f41c..c9a7ff6 100644
@@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <[email protected]>");
 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;

Signature · 1 line

2.3.5

Evgeniy Polyakov

Acked-by on v2 1/1

2015-04-22 23:28 UTC #5 lore raw

Re: [PATCH v2] w1: introduce an ability to specify microseconds bus scanning intervals

Looks good to me. Greg, please pull it into your tree.

Acked-by Evgeniy Polyakov <[email protected]>

23.04.2015, 00:56, "Dmitry Khromov" <[email protected]>:

Quoted 68 lines

Signed-off-by Dmitry Khromov <[email protected]>

---
drivers/w1/w1.c | 17 ++++++++++++++++-

 1 file changed, 16 insertions(+), 1 deletion(-)

drivers/w1/w1.c +16 -2

index 181f41c..c9a7ff6 100644
@@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <[email protected]>");
  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

Greg KH

2015-04-23 09:20 UTC #6 lore raw

Re: [PATCH v2] w1: introduce an ability to specify microseconds bus scanning intervals

In reply to Dmitry Khromov

Quoted 4 lines · Dmitry Khromov

Signed-off-by Dmitry Khromov <[email protected]>
---
 drivers/w1/w1.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

You added a new sysfs file, without any documentation about it added to Documentation/ABI, nor any reason why this needs to be done in the changelog entry for the patch.

I need _some_ kind of information here, sorry, I can't take this as-is.

thanks,

greg k-h

Dmitry Khromov

author

2015-04-23 11:30 UTC #7 lore raw

Re: [PATCH v2] w1: introduce an ability to specify microseconds bus scanning intervals

Quoted 9 lines · Greg KH

Quoted 4 lines · Dmitry Khromov
Signed-off-by Dmitry Khromov <[email protected]>
---
  drivers/w1/w1.c | 17 ++++++++++++++++-
  1 file changed, 16 insertions(+), 1 deletion(-)
You added a new sysfs file, without any documentation about it added to Documentation/ABI, nor any reason why this needs to be done in the changelog entry for the patch.

Sorry for that, the complete reason was given in the original version of the patch, I've added a short summary in the changelog for v3. Thanks for reminding about the documentation. I've added a short description and minor cosmetics to Documentation/w1/w1.generic to give a slightly more detailed idea on what's going on during the bus scan.

Please review.

Signature · 2 lines

Regards,
- Dmitry

Dmitry Khromov

author

2015-04-23 11:40 UTC #8 lore raw

PATCH v3 1/1 w1: introduce an ability to specify microseconds bus scanning intervals

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 <[email protected]>

---
 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

Documentation/ABI/stable/sysfs-bus-w1 new file +11 -0

new file mode 100644
index 0000000..140d85b
@@ -0,0 +1,11 @@
+What:		/sys/bus/w1/devices/.../w1_master_timeout_us
+Date:		April 2015
+Contact:	Dmitry Khromov <[email protected]>
+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

Documentation/w1/w1.generic +19 ~~-11~~

index b2033c6..b3ffaf8 100644
@@ -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
 ------------------------------------------------------------------

drivers/w1/w1.c +16 -1

index 181f41c..c9a7ff6 100644
@@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <[email protected]>");
 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;

Signature · 1 line

2.3.5

Dmitry Khromov

author

2015-05-12 19:30 UTC #9 lore raw

PATCH v3 1/1 w1: introduce an ability to specify microseconds bus scanning intervals

In reply to Greg KH

Signed-off-by Dmitry Khromov <[email protected]>

---
 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

Documentation/ABI/stable/sysfs-bus-w1 new file +11 -0

new file mode 100644
index 0000000..140d85b
@@ -0,0 +1,11 @@
+What:		/sys/bus/w1/devices/.../w1_master_timeout_us
+Date:		April 2015
+Contact:	Dmitry Khromov <[email protected]>
+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

Documentation/w1/w1.generic +19 ~~-11~~

index b2033c6..b3ffaf8 100644
@@ -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
 ------------------------------------------------------------------

drivers/w1/w1.c +16 -1

index 181f41c..c9a7ff6 100644
@@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <[email protected]>");
 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;

Signature · 1 line

2.3.5

Evgeniy Polyakov

Acked-by on v3 1/1

2015-05-13 15:01 UTC #10 lore raw

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

12.05.2015, 22:30, "Dmitry Khromov" <[email protected]>:

Quoted 5 lines

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 <[email protected]>

Greg, please pull it upstream

Acked-by Evgeniy Polyakov <[email protected]>

[email protected]

2015-05-13 15:31 UTC #11 lore raw

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

Quoted 11 lines · Evgeniy Polyakov

Hi
12.05.2015, 22:30, "Dmitry Khromov" <[email protected]>:
Quoted 5 lines
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 <[email protected]>
Greg, please pull it upstream
Acked-by Evgeniy Polyakov <[email protected]>

Ok, will do.