From 125ff8087fca28e922e7ad6e082efcf04fe2f0f4 Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Sat, 23 Feb 2008 10:57:53 +0100 Subject: hwmon: Update the sysfs interface documentation * Document the characteristics of libsensors 3.0.0 and 3.0.1. * The sysfs interface is no longer subject to changes. Signed-off-by: Jean Delvare Acked-by: Juerg Haefliger Signed-off-by: Mark M. Hoffman --- Documentation/hwmon/sysfs-interface | 33 +++++++++++++-------------------- 1 file changed, 13 insertions(+), 20 deletions(-) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/sysfs-interface b/Documentation/hwmon/sysfs-interface index f4a8ebc1ef1a..2d845730d4e0 100644 --- a/Documentation/hwmon/sysfs-interface +++ b/Documentation/hwmon/sysfs-interface @@ -2,17 +2,12 @@ Naming and data format standards for sysfs files ------------------------------------------------ The libsensors library offers an interface to the raw sensors data -through the sysfs interface. See libsensors documentation and source for -further information. As of writing this document, libsensors -(from lm_sensors 2.8.3) is heavily chip-dependent. Adding or updating -support for any given chip requires modifying the library's code. -This is because libsensors was written for the procfs interface -older kernel modules were using, which wasn't standardized enough. -Recent versions of libsensors (from lm_sensors 2.8.2 and later) have -support for the sysfs interface, though. - -The new sysfs interface was designed to be as chip-independent as -possible. +through the sysfs interface. Since lm-sensors 3.0.0, libsensors is +completely chip-independent. It assumes that all the kernel drivers +implement the standard sysfs interface described in this document. +This makes adding or updating support for any given chip very easy, as +libsensors, and applications using it, do not need to be modified. +This is a major improvement compared to lm-sensors 2. Note that motherboards vary widely in the connections to sensor chips. There is no standard that ensures, for example, that the second @@ -35,19 +30,17 @@ access this data in a simple and consistent way. That said, such programs will have to implement conversion, labeling and hiding of inputs. For this reason, it is still not recommended to bypass the library. -If you are developing a userspace application please send us feedback on -this standard. - -Note that this standard isn't completely established yet, so it is subject -to changes. If you are writing a new hardware monitoring driver those -features can't seem to fit in this interface, please contact us with your -extension proposal. Keep in mind that backward compatibility must be -preserved. - Each chip gets its own directory in the sysfs /sys/devices tree. To find all sensor chips, it is easier to follow the device symlinks from /sys/class/hwmon/hwmon*. +Up to lm-sensors 3.0.0, libsensors looks for hardware monitoring attributes +in the "physical" device directory. Since lm-sensors 3.0.1, attributes found +in the hwmon "class" device directory are also supported. Complex drivers +(e.g. drivers for multifunction chips) may want to use this possibility to +avoid namespace pollution. The only drawback will be that older versions of +libsensors won't support the driver in question. + All sysfs values are fixed point numbers. There is only one value per file, unlike the older /proc specification. -- cgit v1.2.3