Messages in this thread Patch in this message | | | Date | Tue, 14 Apr 2015 10:40:55 +0300 | From | Dmitry Khromov <> | Subject | [PATCH] Introduce an ability to specify microseconds bus scanning intervals in w1 core |
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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 <dk@icelogic.net> Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
drivers/w1/w1.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) --- diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c index 181f41c..73b4e2d 100644 --- a/drivers/w1/w1.c +++ b/drivers/w1/w1.c @@ -46,11 +46,15 @@ MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>"); 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;
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