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authorJean Delvare <khali@linux-fr.org>2008-02-23 10:57:53 +0100
committerMark M. Hoffman <mhoffman@lightlink.com>2008-06-19 06:50:31 -0400
commit125ff8087fca28e922e7ad6e082efcf04fe2f0f4 (patch)
tree1bbe653c5542fa7cd2d7303c177fc6a54fae5bfd
parented4ec814e45ae8b1596aea0a29b92f6c3614acaa (diff)
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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 <khali@linux-fr.org> Acked-by: Juerg Haefliger <juergh at gmail.com> Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>
-rw-r--r--Documentation/hwmon/sysfs-interface33
1 files changed, 13 insertions, 20 deletions
diff --git a/Documentation/hwmon/sysfs-interface b/Documentation/hwmon/sysfs-interface
index f4a8ebc..2d84573 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.