From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752886AbbDNHsN (ORCPT ); Tue, 14 Apr 2015 03:48:13 -0400 Received: from forward4o.mail.yandex.net ([37.140.190.33]:38130 "EHLO forward4o.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751664AbbDNHsE (ORCPT ); Tue, 14 Apr 2015 03:48:04 -0400 X-Greylist: delayed 423 seconds by postgrey-1.27 at vger.kernel.org; Tue, 14 Apr 2015 03:48:04 EDT Authentication-Results: smtp2o.mail.yandex.net; dkim=pass header.i=@icelogic.net Message-ID: <552CC487.70402@icelogic.net> Date: Tue, 14 Apr 2015 10:40:55 +0300 From: Dmitry Khromov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:36.0) Gecko/20100101 Firefox/36.0 SeaMonkey/2.33.1 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org CC: gregkh@linuxfoundation.org, Evgeniy Polyakov Subject: [PATCH] Introduce an ability to specify microseconds bus scanning intervals in w1 core References: <55292A69.5020106@icelogic.net> <1040571428797306@web8j.yandex.ru> In-Reply-To: <1040571428797306@web8j.yandex.ru> Content-Type: text/plain; charset=KOI8-R; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Acked-by: Evgeniy Polyakov 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 "); 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;