Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761774AbYGKNyx (ORCPT ); Fri, 11 Jul 2008 09:54:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759424AbYGKNsR (ORCPT ); Fri, 11 Jul 2008 09:48:17 -0400 Received: from zbr.yandex.ru ([213.180.219.33]:34991 "EHLO gavana.yandex.ru" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759437AbYGKNr6 (ORCPT ); Fri, 11 Jul 2008 09:47:58 -0400 From: Evgeniy Polyakov To: linux-kernel@vger.kernel.org Cc: Andrew Morton , David Fries , Evgeniy Polyakov Subject: [PATCH 6/30] W1: feature, w1_therm.c use strong pullup and documentation Date: Fri, 11 Jul 2008 17:51:21 +0400 Message-Id: <12157843061218-git-send-email-johnpol@2ka.mipt.ru> X-Mailer: git-send-email 1.5.2.5 In-Reply-To: <12157843054074-git-send-email-johnpol@2ka.mipt.ru> References: <12157843054074-git-send-email-johnpol@2ka.mipt.ru> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4469 Lines: 124 Added strong pullup to thermal sensor driver and general documentation on the sensor. Signed-off-by: David Fries Signed-off-by: Evgeniy Polyakov --- Documentation/w1/00-INDEX | 2 + Documentation/w1/slaves/00-INDEX | 4 +++ Documentation/w1/slaves/w1_therm | 41 ++++++++++++++++++++++++++++++++++++++ drivers/w1/slaves/w1_therm.c | 15 ++++++++++++- 4 files changed, 60 insertions(+), 2 deletions(-) diff --git a/Documentation/w1/00-INDEX b/Documentation/w1/00-INDEX index 5270cf4..cb49802 100644 --- a/Documentation/w1/00-INDEX +++ b/Documentation/w1/00-INDEX @@ -1,5 +1,7 @@ 00-INDEX - This file +slaves/ + - Drivers that provide support for specific family codes. masters/ - Individual chips providing 1-wire busses. w1.generic diff --git a/Documentation/w1/slaves/00-INDEX b/Documentation/w1/slaves/00-INDEX new file mode 100644 index 0000000..f8101d6 --- /dev/null +++ b/Documentation/w1/slaves/00-INDEX @@ -0,0 +1,4 @@ +00-INDEX + - This file +w1_therm + - The Maxim/Dallas Semiconductor ds18*20 temperature sensor. diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm new file mode 100644 index 0000000..0403aaa --- /dev/null +++ b/Documentation/w1/slaves/w1_therm @@ -0,0 +1,41 @@ +Kernel driver w1_therm +==================== + +Supported chips: + * Maxim ds18*20 based temperature sensors. + +Author: Evgeniy Polyakov + + +Description +----------- + +w1_therm provides basic temperature conversion for ds18*20 devices. +supported family codes: +W1_THERM_DS18S20 0x10 +W1_THERM_DS1822 0x22 +W1_THERM_DS18B20 0x28 + +Support is provided through the sysfs w1_slave file. Each open and +read sequence will initiate a temperature conversion then provide two +lines of ASCII output. The first line contains the nine hex bytes +read along with a calculated crc value and YES or NO if it matched. +If the crc matched the returned values are retained. The second line +displays the retained values along with a temperature in millidegrees +Centigrade after t=. + +Parasite powered devices are limited to one slave performing a +temperature conversion at a time. If none of the devices are parasite +powered it would be possible to convert all the devices at the same +time and then go back to read individual sensors. That isn't +currently supported. The driver also doesn't support reduced +precision (which would also reduce the conversion time). + +The module parameter strong_pullup can be set to 0 to disable the +strong pullup or 1 to enable. If enabled the 5V strong pullup will be +enabled when the conversion is taking place provided the master driver +must support the strong pullup (or it falls back to a pullup +resistor). The DS18b20 temperature sensor specification lists a +maximum current draw of 1.5mA and that a 5k pullup resistor is not +sufficient. The strong pullup is designed to provide the additional +current required. diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c index fb28aca..e87f464 100644 --- a/drivers/w1/slaves/w1_therm.c +++ b/drivers/w1/slaves/w1_therm.c @@ -37,6 +37,14 @@ MODULE_LICENSE("GPL"); MODULE_AUTHOR("Evgeniy Polyakov "); MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol, temperature family."); +/* Allow the strong pullup to be disabled, but default to enabled. + * If it was disabled a parasite powered device might not get the require + * current to do a temperature conversion. If it is enabled parasite powered + * devices have a better chance of getting the current required. + */ +static int w1_strong_pullup = 1; +module_param_named(strong_pullup, w1_strong_pullup, int, 0); + static u8 bad_roms[][9] = { {0xaa, 0x00, 0x4b, 0x46, 0xff, 0xff, 0x0c, 0x10, 0x87}, {} @@ -192,9 +200,12 @@ static ssize_t w1_therm_read_bin(struct kobject *kobj, int count = 0; unsigned int tm = 750; + /* 750ms strong pullup (or delay) after the convert */ + if (w1_strong_pullup) + w1_next_pullup(dev, tm); w1_write_8(dev, W1_CONVERT_TEMP); - - msleep(tm); + if (!w1_strong_pullup) + msleep(tm); if (!w1_reset_select_slave(sl)) { -- 1.4.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/