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authorLinus Torvalds <torvalds@linux-foundation.org>2014-06-08 22:31:16 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-08 22:31:16 +0400
commit3f17ea6dea8ba5668873afa54628a91aaa3fb1c0 (patch)
treeafbeb2accd4c2199ddd705ae943995b143a0af02 /Documentation/hwmon/hwmon-kernel-api.txt
parent1860e379875dfe7271c649058aeddffe5afd9d0d (diff)
parent1a5700bc2d10cd379a795fd2bb377a190af5acd4 (diff)
downloadlinux-3f17ea6dea8ba5668873afa54628a91aaa3fb1c0.tar.xz
Merge branch 'next' (accumulated 3.16 merge window patches) into master
Now that 3.15 is released, this merges the 'next' branch into 'master', bringing us to the normal situation where my 'master' branch is the merge window. * accumulated work in next: (6809 commits) ufs: sb mutex merge + mutex_destroy powerpc: update comments for generic idle conversion cris: update comments for generic idle conversion idle: remove cpu_idle() forward declarations nbd: zero from and len fields in NBD_CMD_DISCONNECT. mm: convert some level-less printks to pr_* MAINTAINERS: adi-buildroot-devel is moderated MAINTAINERS: add linux-api for review of API/ABI changes mm/kmemleak-test.c: use pr_fmt for logging fs/dlm/debug_fs.c: replace seq_printf by seq_puts fs/dlm/lockspace.c: convert simple_str to kstr fs/dlm/config.c: convert simple_str to kstr mm: mark remap_file_pages() syscall as deprecated mm: memcontrol: remove unnecessary memcg argument from soft limit functions mm: memcontrol: clean up memcg zoneinfo lookup mm/memblock.c: call kmemleak directly from memblock_(alloc|free) mm/mempool.c: update the kmemleak stack trace for mempool allocations lib/radix-tree.c: update the kmemleak stack trace for radix tree allocations mm: introduce kmemleak_update_trace() mm/kmemleak.c: use %u to print ->checksum ...
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+The Linux Hardware Monitoring kernel API.
+=========================================
+
+Guenter Roeck
+
+Introduction
+------------
+
+This document describes the API that can be used by hardware monitoring
+drivers that want to use the hardware monitoring framework.
+
+This document does not describe what a hardware monitoring (hwmon) Driver or
+Device is. It also does not describe the API which can be used by user space
+to communicate with a hardware monitoring device. If you want to know this
+then please read the following file: Documentation/hwmon/sysfs-interface.
+
+For additional guidelines on how to write and improve hwmon drivers, please
+also read Documentation/hwmon/submitting-patches.
+
+The API
+-------
+Each hardware monitoring driver must #include <linux/hwmon.h> and, in most
+cases, <linux/hwmon-sysfs.h>. linux/hwmon.h declares the following
+register/unregister functions:
+
+struct device *hwmon_device_register(struct device *dev);
+struct device *
+hwmon_device_register_with_groups(struct device *dev, const char *name,
+ void *drvdata,
+ const struct attribute_group **groups);
+
+struct device *
+devm_hwmon_device_register_with_groups(struct device *dev,
+ const char *name, void *drvdata,
+ const struct attribute_group **groups);
+
+void hwmon_device_unregister(struct device *dev);
+void devm_hwmon_device_unregister(struct device *dev);
+
+hwmon_device_register registers a hardware monitoring device. The parameter
+of this function is a pointer to the parent device.
+This function returns a pointer to the newly created hardware monitoring device
+or PTR_ERR for failure. If this registration function is used, hardware
+monitoring sysfs attributes are expected to have been created and attached to
+the parent device prior to calling hwmon_device_register. A name attribute must
+have been created by the caller.
+
+hwmon_device_register_with_groups is similar to hwmon_device_register. However,
+it has additional parameters. The name parameter is a pointer to the hwmon
+device name. The registration function wil create a name sysfs attribute
+pointing to this name. The drvdata parameter is the pointer to the local
+driver data. hwmon_device_register_with_groups will attach this pointer
+to the newly allocated hwmon device. The pointer can be retrieved by the driver
+using dev_get_drvdata() on the hwmon device pointer. The groups parameter is
+a pointer to a list of sysfs attribute groups. The list must be NULL terminated.
+hwmon_device_register_with_groups creates the hwmon device with name attribute
+as well as all sysfs attributes attached to the hwmon device.
+
+devm_hwmon_device_register_with_groups is similar to
+hwmon_device_register_with_groups. However, it is device managed, meaning the
+hwmon device does not have to be removed explicitly by the removal function.
+
+hwmon_device_unregister deregisters a registered hardware monitoring device.
+The parameter of this function is the pointer to the registered hardware
+monitoring device structure. This function must be called from the driver
+remove function if the hardware monitoring device was registered with
+hwmon_device_register or with hwmon_device_register_with_groups.
+
+devm_hwmon_device_unregister does not normally have to be called. It is only
+needed for error handling, and only needed if the driver probe fails after
+the call to devm_hwmon_device_register_with_groups.
+
+The header file linux/hwmon-sysfs.h provides a number of useful macros to
+declare and use hardware monitoring sysfs attributes.
+
+In many cases, you can use the exsting define DEVICE_ATTR to declare such
+attributes. This is feasible if an attribute has no additional context. However,
+in many cases there will be additional information such as a sensor index which
+will need to be passed to the sysfs attribute handling function.
+
+SENSOR_DEVICE_ATTR and SENSOR_DEVICE_ATTR_2 can be used to define attributes
+which need such additional context information. SENSOR_DEVICE_ATTR requires
+one additional argument, SENSOR_DEVICE_ATTR_2 requires two.
+
+SENSOR_DEVICE_ATTR defines a struct sensor_device_attribute variable.
+This structure has the following fields.
+
+struct sensor_device_attribute {
+ struct device_attribute dev_attr;
+ int index;
+};
+
+You can use to_sensor_dev_attr to get the pointer to this structure from the
+attribute read or write function. Its parameter is the device to which the
+attribute is attached.
+
+SENSOR_DEVICE_ATTR_2 defines a struct sensor_device_attribute_2 variable,
+which is defined as follows.
+
+struct sensor_device_attribute_2 {
+ struct device_attribute dev_attr;
+ u8 index;
+ u8 nr;
+};
+
+Use to_sensor_dev_attr_2 to get the pointer to this structure. Its parameter
+is the device to which the attribute is attached.