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libsysfs.txt
System Utilities sysfs Library - libsysfs ========================================= Version: 2.1.0 August 22, 2006 Contents -------- 1. Introduction 2. Requirements 3. Definitions 4. Overview 5. Data Structures 5.1 Attribute Data Structure 5.2 Bus Data Structure 5.3 Class Data Structures 5.4 Device Data Structure 5.5 Driver Data Structure 5.6 Module Data Structure 6. Functions 6.1 Calling Conventions in Libsysfs 6.2 Utility Functions 6.3 Attribute Functions 6.4 Bus Functions 6.5 Class Functions 6.6 Device Functions 6.7 Driver Functions 6.8 Module functions 7. Dlists 7.1 Navigating a dlist 7.2 Custom sorting using dlist_sort_custom() 7.3 Custom filtering and sorting using dlist_filter_sort() 8. Usage 9. Testsuite 10. Conclusion 1. Introduction --------------- Libsysfs' purpose is to provide a consistent and stable interface for querying system device information exposed through the sysfs filesystem. The library implements functions for querying filesystem information, such as reading directories and files. It also contains routines for working with buses, classes, and the device tree. 2. Requirements --------------- The library must satisfy the following requirements: - It must provide a stable programming interfaces that applications can be built upon. - It must provide functions to retrieve device Vital Product Data (VPD) information for Error Log Analysis (ELA) support. ELA will provide device driver and device bus address information. - It must provide access to all system devices and information exposed by sysfs. - It must provide a function to find sysfs' current mount point. - It must provide a function for udev to retrieve a device's major and minor numbers. 3. Definitions -------------- - sysfs: Sysfs is a virtual filesystem in 2.5+ Linux kernels that presents a hierarchical representation of all system physical and virtual devices. It presents system devices by bus, by class, and by topology. Callbacks to device drivers are exposed as files in device directories. Sysfs, for all purposes, is our tree of system devices. For more information, please see: http://www.kernel.org/pub/linux/kernel/people/mochel/doc/ - udev: Udev is Greg Kroah-Hartman's User Space implementation of devfs. Udev creates /dev nodes for devices upon Hotplug events. The Hotplug event provides udev with a sysfs directory location of the device. Udev must use that directory to grab device's major and minor number, which it will use to create the /dev node. For more information, please see: http://www.kernel.org/pub/linux/utils/kernel/hotplug/ Udev provides persistent device naming based on a set of user specified rules. The rules a device name is based on could one or a combination of a number of parameters such as the bus the device is on, the serial number of the device (in case of USB), the vendor name (in case of SCSI) and so on. Udev uses Libsysfs to retrieve relevent information to appropriately name devices. 4. Overview ----------- Libsysfs grew from a common need. There are several applications under development that need access to sysfs and system devices. Udev, on a hotplug event, must take a sysfs device path and create a /dev node. Our diagnostic client needs to list all system devices. Finally, our Error Log Analysis piece is required to retrieve VPD information for a failing device. We divided to create a single library interface rather than having these separate applications create their own accesses to sysfs involving reading directories and files. Libsysfs will also provide stability for applications to be built upon. Sysfs currently doesn't enforce any standards for callback or file names. File names change depending on bus or class. Sysfs is also changing, it is currently being developed. Libsysfs will provide a stable interface to applications while allowing sysfs to change underneath it. Like sysfs, the library will provide devices to applications by bus, by class, and by topology. The library will function similar to directories and files that lie underneath it. To query a device on a PCI bus, one would "open" the bus to scan or read devices and "close" the bus when completed. Besides supplying functions to retrieve devices, the library will also provide some utility functions like getting sysfs mount point. A paper on Libsysfs was presented at Linux.Conf.Au 2004 (Adelaide, January 2004). The paper is available online at: http://oss.software.ibm.com/linux/papers/libsysfs/libsysfs-linuxconfau2004.pdf 5. Data Structures ------------------ Libsysfs will classify system devices following sysfs' example, dividing them by bus, class, and devices. The library presents this information generically. It doesn't, for example, differentiate between PCI and USB buses. Device attributes are presented with values as they are exposed by sysfs, the values are not formatted. The library will provide standard definitions for working with sysfs and devices, here's some examples: #define SYSFS_FSTYPE_NAME "sysfs" #define SYSFS_PROC_MNTS "/proc/mounts" #define SYSFS_BUS_NAME "bus" #define SYSFS_CLASS_NAME "class" #define SYSFS_BLOCK_NAME "block" #define SYSFS_DEVICES_NAME "devices" #define SYSFS_DRIVERS_NAME "drivers" #define SYSFS_NAME_ATTRIBUTE "name" #define SYSFS_MOD_PARM_NAME "parameters" #define SYSFS_MOD_SECT_NAME "sections" #define SYSFS_UNKNOWN "unknown" #define SYSFS_PATH_ENV "SYSFS_PATH" The library uses some definitions to mark maximum size of a sysfs name or path length: #define SYSFS_PATH_MAX 256 #define SYSFS_NAME_LEN 64 #define SYSFS_BUS_ID_SIZE 32 NOTE: a. As of release 0.4.0 of sysfsutils, a number of changes have been made so that the dlists and "directory" references in all libsysfs's structures are not populated until such time that it is absolutely necessary. Hence, these elements may not contain valid data at all times (as was the case before). b. As of release 1.0.0 of sysfsutils, all dlists in the library are sorted in alphabetical order. It is now a requirement that the "name" and "path" be the first two elements of all libsysfs structures. c. There has been a major overhaul with 2.0.0 release of sysfsutils. We now have a much leaner and meaner library without the overhead of the sysfs_directory and related structures. The API list has also been pruned to contain the most frequently used calls and the lists are not populated all at once. This has lead to enormous speed improvements as well as reduction in the number of system calls. 5.1 Attribute Data Structure ------------------------------------------- The library implements structure to represent sysfs files. A file in sysfs represents a device or driver attribute. Attributes can be read only, write only, or read and write. File data can be ASCII and binary. The library has the following structure to represent files: struct sysfs_attribute { char name[SYSFS_NAME_LEN]; char path[SYSFS_PATH_MAX]; char *value; unsigned short len; /* value length */ enum sysfs_attribute_method method; /* show and store */ }; Path represents the file/attribute's full path. Value is used when reading from or writing to an attribute. "len" is the length of data in "value". Method is an enum for defining if the attribute supports show(read) and/or store(write). 5.2 Bus Data Structure ---------------------- All buses look similar in sysfs including lists of devices and drivers, therefore we use the following structure to represent all sysfs buses: struct sysfs_bus { char name[SYSFS_NAME_LEN]; char path[SYSFS_PATH_MAX]; struct dlist *attrlist; /* Private: for internal use only */ struct dlist *drivers; struct dlist *devices; }; The sysfs_bus structure contains the bus "name", while the "path" to bus directory is also stored. It also contains lists of devices on the bus and drivers that are registered on it. 5.3 Class Data Structures ------------------------- The library uses two data structures to represent classes in sysfs. Sysfs classes contains a class directory like "net" or "scsi_host" and then class devices like "eth0", "lo", or "eth1" for the "net" class. struct sysfs_class { char name[SYSFS_NAME_LEN]; char path[SYSFS_PATH_MAX]; struct dlist *attrlist; /* Private: for internal use only */ struct dlist *devices; }; The sysfs_class represents device classes in sysfs like "net". It contains the class "name", "path" to the class and a list of class devices struct sysfs_class_device { char name[SYSFS_NAME_LEN]; char path[SYSFS_PATH_MAX]; struct dlist *attrlist; char classname[SYSFS_NAME_LEN]; /* Private: for internal use only */ struct sysfs_class_device *parent; struct sysfs_device *sysdevice; /* NULL if virtual */ }; A class device isn't the same as a sysfs_device, it's specific to the class in which it belongs. The class device structure contains the name of the class the class device belongs to and its sysfs_device reference. It also contains the name of the class device - like "eth0", its parent (if present). 5.4 Device Data Structure ------------------------- The sysfs_device structure represents a system device that's exposed in sysfs under the /sys/devices directory structure. struct sysfs_device { char name[SYSFS_NAME_LEN]; char path[SYSFS_PATH_MAX]; struct dlist *attrlist; char bus_id[SYSFS_NAME_LEN]; char bus[SYSFS_NAME_LEN]; char driver_name[SYSFS_NAME_LEN]; char subsystem[SYSFS_NAME_LEN]; /* Private: for internal use only */ struct sysfs_device *parent; struct dlist *children; }; The sysfs_device structure contains a "parent" pointer, a list of child devices, if any, device's directory, its bus id - which is the name of device's directory, the bus name on which this device is registered and its driver name. The device structure also contains the absolute path to the device. 5.5 Driver Data Structure ------------------------- The sysfs_driver structure represents a device driver. struct sysfs_driver { char name[SYSFS_NAME_LEN]; char path[SYSFS_PATH_MAX]; struct dlist *attrlist; char bus[SYSFS_NAME_LEN]; /* Private: for internal use only */ struct sysfs_module *module; struct dlist *devices; }; The sysfs_driver structure contains a list of devices that use this driver, the name of the driver, the module it is using and a list of attributes for the driver. 5.6 Module Data Structure ------------------------- The sysfs_module structure represents the module loaded in the system. struct sysfs_module { char name[SYSFS_NAME_LEN]; char path[SYSFS_PATH_MAX]; struct dlist *attrlist; struct dlist *parmlist; struct dlist *sections; }; The sysfs_module structure contains a list of attributes, parameters and sections used by the corresponding module. It also contains name of the module, its path. The following functions can be used to retrive the information related to the module. struct dlist *sysfs_get_module_parms(struct sysfs_module *module) struct dlist *sysfs_get_module_sections(struct sysfs_module *module) struct dlist *sysfs_get_module_attributes(struct sysfs_module *module) 6. Functions ------------ Libsysfs will provide functions to access system devices by bus, by class, and by device. Functions will act like accessing directories and files, using "open" and "close". Open returns a structure and close is used to clean that structure up. 6.1 Calling Conventions in Libsysfs ----------------------------------- Libsysfs uses a simple API calling convention. APIs are classified to be one of "open", "get", "close" types. The convention is as follows: a. All "open" APIs have a corresponding "close" API. b. References obtained using "get" calls should not be closed explicitly. c. All "opened" references have to be closed with a call to their corresponding "close" call. This takes care of freeing structure references obtained with "get" calls. 6.2 Utility Functions --------------------- The library will provide a few utility functions for working with sysfs. ------------------------------------------------------------------------------- Name: sysfs_get_mnt_path Description: Function finds the mount path for filesystem type "sysfs". Arguments: char *mnt_path Mount path buffer size_t len Size of mount path buffer Returns: Zero with success. -1 with error. Errno will be set with error: - EINVAL for invalid argument, if buffer is NULL or if len is zero Prototype: sysfs_get_mnt_path(char *mnt_path, size_t len); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_name_from_path Description: Function returns the last directory or file name from the included path. Arguments: const char *path Path to parse name from char *name Buffer to put parsed name into size_t *len Size of name buffer Returns: 0 with success. -1 on Error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: int sysfs_get_name_from_path(const char *path, char *name, size_t *len) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_link Description: Sysfs readlink function, reads the link at supplied path and returns its target path. Arguments: const char *path Link's path char *target Buffer to place link's target size_t len Size of target buffer Returns: 0 with success -1 with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: int sysfs_get_link(const char *path, char *target, size_t len) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_close_list Description: Closes a given dlist. This can be used as a generic list close routine. Arguments: struct dlist *list List to be closed Prototype: void sysfs_close_list(struct dlist *list) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_path_is_dir Description: Utility function to verify if a given path is to a directory. Arguments: const char *path Path to verify Returns: 0 on success, 1 on error - EINVAL for invalid arguments Prototype: int sysfs_path_is_dir(const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_path_is_file Description: Utility function to verify if a given path is to a file. Arguments: const char *path Path to verify Returns: 0 on success, 1 on error - EINVAL for invalid arguments Prototype: int sysfs_path_is_file(const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_path_is_link Description: Utility function to verify if a given path is to a link. Arguments: const char *path Path to verify Returns: 0 on success, 1 on error - EINVAL for invalid arguments Prototype: int sysfs_path_is_link(const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_directory_list Description: Utility function to get list of all directories under path. Arguments: const char *path Path to read Returns: Directory list on success, NULL on error Prototype: struct dlist *sysfs_open_directory_list(const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_link_list Description: Utility function to get list of all links under path. Arguments: const char *path Path to read Returns: Links list on success, NULL on error Prototype: struct dlist *sysfs_open_link_list(const char *path) ------------------------------------------------------------------------------- 6.3 Attribute Functions ------------------------ Libsysfs provides a set of functions to open, read, and close attributes in sysfs. These functions mirror their filesystem function counterparts. Along with the usual open, read, and close functions, libsysfs provides a couple other functions for accessing attribute values. ------------------------------------------------------------------------------- Name: sysfs_open_attribute Description: Opens up a file in sysfs and creates a sysfs_attribute structure. File isn't read with this function. Arguments: const char *path File/Attribute's path Returns: struct sysfs_attribute * with success. NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_attribute *sysfs_open_attribute(const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_close_attribute Description: Cleans up and closes sysfs_attribute structure. Arguments: struct sysfs_attribute *sysattr Attribute to close Prototype: void sysfs_close_attribute(struct sysfs_attribute *sysattr) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_read_attribute Description: Reads the supplied attribute. Since the maximum transfer from a sysfs attribute is a pagesize, function reads in up to a page from the file and stores it in the "value" field in the attribute. Arguments: struct sysfs_attribute *sysattr Attribute to read Returns: 0 with success. -1 with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: int sysfs_read_attribute(struct sysfs_attribute *sysattr) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_write_attribute Description: Writes to the supplied attribute. Function validates if the given attribute is writable, and writes the new value to the attribute. Value to write as well as its length is user supplied. In case the length written is not equal to the length requested to be written, the original value is restored and an error is returned. Arguments: struct sysfs_attribute *sysattr Attribute to write to const char *new_value sysattr's new value size_t len Length of "new_value" Returns: 0 with success. -1 with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: int sysfs_write_attribute(struct sysfs_attribute *sysattr, const char *new_value, size_t len) ------------------------------------------------------------------------------- 6.4 Bus Functions ----------------- The library provides a functions for viewing buses represented in sysfs. The sysfs_open_bus opens a bus in the /sys/bus directory, such as "pci", "usb", or "scsi". The open command returns a sysfs_bus structure that contains a list of the bus' devices. The sysfs_close_bus function is used to clean up the bus structure. Given a device or a driver, functions are provided to determine what bus they are on. ------------------------------------------------------------------------------- Name: sysfs_open_bus Description: Function opens up one of the buses represented in sysfs in the /sys/bus directory. It returns a sysfs_bus structure that includes a list of bus devices and drivers. Arguments: const char *name Bus name to open, like "pci"... Returns: struct sysfs_bus * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_bus *sysfs_open_bus(const char *name) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_close_bus Description: Function closes up the sysfs_bus structure including its devices, and drivers and the list of attributes. Arguments: sysfs_bus *bus Bus structure to close Prototype: void sysfs_close_bus(struct sysfs_bus *bus) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_bus_devices Description: Function returns a list of devices that are registered with this bus. Arguments: struct sysfs_bus *bus Bus whose devices list to return Returns: struct dlist * of sysfs_devices on success NULL with error. Errno will be sent with error, returning - EINVAL for invalid arguments Prototype: struct dlist *sysfs_get_bus_devices(struct sysfs_bus *bus) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_bus_drivers Description: Function returns a list of drivers that are registered with this bus. Arguments: struct sysfs_bus *bus Bus whose drivers list to return Returns: struct dlist * of sysfs_drivers on success NULL with error. Errno will be sent with error, returning - EINVAL for invalid arguments Prototype: struct dlist *sysfs_get_bus_drivers(struct sysfs_bus *bus) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_bus_device Description: Function takes a sysfs_bus structure(obtained on a successful return from a sysfs_open_bus() call) and looks for the given device on this bus. On success, it returns a sysfs_device structure corresponding to the device. Arguments: struct sysfs_bus *bus Bus structure on which to search char *id Device to look for Returns: struct sysfs_device * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_device *sysfs_get_bus_device (struct sysfs_bus *bus, char *id) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_bus_driver Description: Function takes a sysfs_bus structure (obtained on a successful return from a sysfs_open_bus() call) and looks for the given driver on this bus. On success, it returns a sysfs_driver structure corresponding to the driver. Arguments: struct sysfs_bus *bus Bus structure on which to search char *drvname Driver to look for Returns: struct sysfs_driver * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_device *sysfs_get_bus_driver (struct sysfs_bus *bus, char *drvname) ------------------------------------------------------------------------------- 6.5 Class Functions ------------------- Libsysfs provides functions to open sysfs classes and their class devices. These functions too operate with open and close, close must be called to clean up the class structures. Given a class device name, functions are provided to determine what class they belong to. Once a class device name and the class it belongs to is known, a function to open the class device is provided. This method can be used when details of a single class device is required. ------------------------------------------------------------------------------- Name: sysfs_open_class Description: Function opens up one of the classes represented in sysfs in the /sys/class directory. It returns a sysfs_class structure that includes a list of class devices. Arguments: const char *name Class name to open, like "net".. Returns: struct sysfs_class * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_class *sysfs_open_class(const char *name) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_close_class Description: Function closes up the sysfs_class structure including its class devices. Arguments: sysfs_class *cls Class structure to close Prototype: void sysfs_close_class(struct sysfs_class *cls); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_class_device_path Description: Function opens up one of the class devices represented in sysfs in sysfs/class/"class"/ directory. It returns a sysfs_class_device structure. Arguments: const char *path Path to class device Returns: struct sysfs_class_device * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_class_device *sysfs_open_class_device_path (const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_close_class_device Description: Function closes up the sysfs_class_device structure. Arguments: sysfs_class_device *dev Class device structure to close Prototype: void sysfs_close_class_device(struct sysfs_class_device *dev) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_class_device Description: Function takes a sysfs_class structure(obtained on a successful return from a sysfs_open_class() call) and looks for the given device in this class. On success, it returns a sysfs_class_device structure corresponding to the class device. Arguments: struct sysfs_class *cls Class on which to search char *name Class device "name" to look for Returns: struct sysfs_class_device * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_class_device *sysfs_get_class_device (struct sysfs_class *cls, char *name) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_class_devices Description: Function returns a list of class devices for the given class. Arguments: struct sysfs_class *cls Class whose class device list is required Returns: struct dlist * of sysfs_class_devices on success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct dlist *sysfs_get_class_devices(struct sysfs_class *cls) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_class_device Description: Given the name of the class on which to look for, this function locates a given class device and returns a sysfs_class_device structure corresponding to the requested class device. NOTE: 1. The sysfs_class_device structure obtained upon successful return from this function has to be closed by calling sysfs_close_class_device(). 2. Class this device belongs to must be known prior to calling this function. Arguments: const char *classname Class on which to search char *name Class device "name" to open Returns: struct sysfs_class_device * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_class_device *sysfs_open_class_device (const char *classname, char *name) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_classdev_device Description: Function returns the sysfs_device reference (if present) for the given class device. Arguments: struct sysfs_class_device *clsdev Class device whose sysfs_device reference is required Returns: struct sysfs_device * on success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_device *sysfs_get_classdev_device (struct sysfs_class_device *clsdev) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_classdev_parent Description: Function returns the sysfs_class_device reference for the parent (if present) of the given class device. Arguments: struct sysfs_class_device *clsdev Class device whose parent reference is required Returns: struct sysfs_class_device * on success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_class_device *sysfs_get_classdev_parent (struct sysfs_class_device *clsdev) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_classdev_attributes Description: Function takes a sysfs_class_device structure and returns a list of attributes for the class device. Arguments: struct sysfs_class_device *cdev Class device for which attributes are required Returns: struct dlist * of attributes with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct dlist *sysfs_get_classdev_attributes (struct sysfs_class_device *cdev) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_classdev_attr Description: Searches supplied class device's attributes by name and returns the attribute. Arguments: struct sysfs_class_device *clsdev Device to search const char *name Attribute name to find Returns: struct sysfs_attribute * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_attribute *sysfs_get_classdev_attr (struct sysfs_class_device *clsdev, const char *name) ------------------------------------------------------------------------------- 6.6 Device Functions -------------------- Devices represent everything in sysfs under /sys/devices, which is a hierarchical view of system devices. Besides the expected open and close functions, libsysfs provides open and close functions for root devices. These functions recursively open or close a device and all of its children. ------------------------------------------------------------------------------- Name: sysfs_open_device_path Description: Opens up a device at a specific path. It opens the device's directory, reads the directory, and returns a sysfs_device structure. Arguments: const char *path Path to device Returns: struct sysfs_device * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_device *sysfs_open_device_path(const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_close_device Description: Function closes up the sysfs_device structure. Arguments: sysfs_device *dev Device structure to close Prototype: void sysfs_close_device(struct sysfs_device *dev) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_device_tree Description: Function opens up the device tree at the specified path. Arguments: const char *path Path at which to open the device tree Returns: struct sysfs_device * with success NULL with error, Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_device *sysfs_open_device_tree(const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_close_device_tree Description: Function closes the device tree originating at the given sysfs_device. Arguments: struct sysfs_device *devroot Device from which the device tree has to be closed Prototype: void sysfs_close_device_tree(struct sysfs_device *devroot) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_device_parent Description: Function returns the sysfs_device reference for the parent (if present) of the given sysfs_device. Arguments: struct sysfs_device *dev sysfs_device whose parent reference is required Returns: struct sysfs_device * on success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_device *sysfs_get_device_parent (struct sysfs_device *dev) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_device_attr Description: Searches supplied device's attributes by name and returns the attribute. Arguments: struct sysfs_device *dev Device to search const char *name Attribute name to find Returns: struct sysfs_attribute * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_attribute *sysfs_get_device_attr (struct sysfs_device *dev, const char *name) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_device_attributes Description: Function takes a sysfs_device structure and returns a list of attributes for the device. Arguments: struct sysfs_device *device Device for which attributes are required Returns: struct dlist * of attributes with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct dlist *sysfs_get_device_attributes (struct sysfs_device *device) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_device Description: Given the name of the bus on which to look for, this function locates a given device and returns a sysfs_device structure corresponding to the requested device. Arguments: const char *bus Bus on which to search const char *bus_id Device to look for Returns: struct sysfs_device * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_device *sysfs_open_device (const char *bus, const char *bus_id) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_device_bus Description: Given a sysfs_device, this function fills in the bus this device is on in the sysfs_device->bus field. Arguments: struct sysfs_device *dev Device whose bus name to find Returns: 0 with success. -1 with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: int sysfs_get_device_bus(struct sysfs_device *dev) ------------------------------------------------------------------------------- 6.7 Driver Functions -------------------- Drivers are represented in sysfs under the /sys/bus/xxx/drivers (xxx being the bus type, such as "pci", "usb, and so on). Functions are provided to open and close drivers. ------------------------------------------------------------------------------- Name: sysfs_open_driver_path Description: Opens driver at specific path. Arguments: const char *path Path to driver Returns: struct sysfs_driver * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_driver *sysfs_open_driver_path(const char *path) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_close_driver Description: Closes and cleans up sysfs_driver structure. Arguments: sysfs_driver *driver Driver structure to close Prototype: void sysfs_close_driver(struct sysfs_driver *driver) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_driver_devices Description: Function returns a list of devices that use this driver. Arguments: struct sysfs_driver *driver Driver whose devices list is required Returns: struct dlist * of sysfs_devices on success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct dlist *sysfs_get_driver_devices (struct sysfs_driver *driver) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_driver_attr Description: Searches supplied driver's attributes by name and returns the attribute. Arguments: struct sysfs_driver *drv Driver to search const char *name Attribute name to find Returns: struct sysfs_attribute * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_attribute *sysfs_get_driver_attr (struct sysfs_driver *drv, const char *name) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_driver_attributes Description: Function takes a sysfs_driver structure and returns a list of attributes for the driver. Arguments: struct sysfs_driver *driver Driver for which attributes are required Returns: struct dlist * of attributes with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct dlist *sysfs_get_driver_attributes (struct sysfs_driver *driver) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_driver Description: Given the name of the bus on which to look for, this function locates a given driver and returns a sysfs_driver structure corresponding to the requested device. NOTE: 1. The sysfs_driver structure obtained upon successful return from this function has to be closed by calling sysfs_close_driver_by_name(). Arguments: const char *bus_name Bus on which to search const char *drv_name Driver name to look for Returns: struct sysfs_driver * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct sysfs_driver *sysfs_open_driver(const char *bus_name, const char *drv_name) ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_driver_module Description: Function takes a sysfs_driver structure and returns the module that the driver is using. Arguments: struct sysfs_driver *drv Driver for which the module details are required Returns: struct sysfs_module * with success NULL with error. Errno will be set with error, returning - EINVAL for invalid arguments Prototype: struct dlist *sysfs_get_driver_module (struct sysfs_driver *drv) ------------------------------------------------------------------------------- 6.8 Module Functions -------------------- Modules are represented in sysfs under the /sys/module. Functions are provided to open and close modules. ------------------------------------------------------------------------------- Name: sysfs_close_module Description: Closes and cleans up the sysfs_module structure Arguments: struct sysfs_module *module sysfs_module device to close Prototype: void sysfs_close_module(struct sysfs_module *module); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_module_path Description: Opens and populates the sysfs_module struct Arguments: const char *path path to the module to open Returns: struct sysfs_module * with success and NULL if error Prototype: struct sysfs_module *sysfs_open_module_path(const char *path); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_open_module Description: Opens specific module on a system Arguments: const char *name Name of the module to open Returns: struct sysfs_module * with success or NULL if error Prototype: struct sysfs_module *sysfs_open_module(const char *name); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_module_parms Description: Get modules list of parameters Arguments: sysfs_module whose parmameter list is required Returns: dlist of parameters on SUCCESS and NULL on error Prototype: struct dlist *sysfs_get_module_parms(struct sysfs_module *module); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_module_sections Description: Get the set of sections for this module Arguments: sysfs_module whose list of sections is required Returns: dlist of sections on SUCCESS and NULL on error Prototype: struct dlist *sysfs_get_module_sections(struct sysfs_module *module); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_module_attributes Description: Get dlist of attributes for the requested sysfs_module Arguments: sysfs_module for which attributes are needed Returns: a dlist of attributes if exists, NULL otherwise Prototype: struct dlist *sysfs_get_module_attributes(struct sysfs_module *module); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_module_attr Description: searches module's attributes by name Arguments: module: to look through name: name of the attribute Returns: sysfs_attribute reference with success or NULL with error Prototype: struct sysfs_attribute *sysfs_get_module_attr (struct sysfs_module *module, const char *name); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_module_parm Description: searches module's parameters by name Arguments: sysfs_module: to look through parm: parameter name Returns: sysfs_attribute on SUCCESS and NULL on error Prototype: struct sysfs_attribute *sysfs_get_module_parm (struct sysfs_module *module, const char *parm); ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Name: sysfs_get_module_section Description: searches module's sections by name Arguments: sysfs_module: to look through section: section name Returns: sysfs_attribute * on SUCCESS and NULL on error Prototype: struct sysfs_attribute *sysfs_get_module_section (struct sysfs_module *module, const char *section); ------------------------------------------------------------------------------- 7 Dlists -------- Libsysfs uses (yet another) list implementation thanks to Eric J Bohm. 7.1 Navigating a dlist ---------------------- Some library functions return a dlist of devices/drivers/attributes, etc. To navigate the list returned the macro "dlist_for_each_data" is to be used. ------------------------------------------------------------------------------ Function/Macro name: dlist_for_each_data Description: Walk the given list, returning a known data type/ structure in each iteration. Arguments: struct dlist *list List pointer data_iterator Data type/structure variable contained in the list datatype Data type/structure contained in the list Returns: On each iteration, "data_iterator" will contain a list element of "datatype" Usage example: The function sysfs_get_classdev_attributes() returns a dlist of attributes. To navigate the list: struct sysfs_attribute *attr = NULL; struct dlist *attrlist = NULL; . . . attrlist = sysfs_get_classdev_attributes (struct sysfs_class_device *cdev) if (attrlist != NULL) { dlist_for_each_data(attrlist, attr, struct sysfs_attribute) { . . . } } ------------------------------------------------------------------------------- 7.2 Custom sorting using dlist_sort_custom() -------------------------------------------- As of release 1.2.0, libsysfs provides a new interface for custom sorting of dlists. The API dlist_sort_custom() has been added for this purpose. Applications that would like to define their own sorter function can now make use of this API. The sorter function must conform to the following prototype: int compare(void *a, void*b) dlist_sort_custom() expects that the compare function will: return >0 for a before b return <0 for b before a return 0 for a == b 7.3 Custom filtering and sorting using dlist_filter_sort() ---------------------------------------------------------- From release 2.0.0, libsysfs provides a new interface for custom filtering and sorting of dlists. This API is similar to scandir() system call. Applications can call this API with the following arguments: the list, pointer to the filter function, pointer to the sorter function as in dlist_sort_custom. The filter function must conform to the following prototype: int filter(void *a) dlist_filter_sort expects that the filter function will: return 0 for unwanted nodes return 1 for required nodes 8. Usage -------- Accessing devices through libsysfs is supposed to mirror accessing devices in the filesystem it represents. Here's a typical order of operation: - get sysfs mount point - "open" sysfs category, ie. bus, class, or device - work with category - "close" sysfs category 9. Testsuite ------------ From version 2.0.0 sysfsutils ships with a comprehensive testsuite. The testsuite shipped as part of the "test" directory of the sysfsutils source package, results in an executable "testlibsysfs". Some of the salient features of the testsuite are: a. Tests _every_ API exported by the library. b. Tests are performed for all possible combinations of input parameters. c. Detailed output is provided for the correct case. d. Facility to redirect output of the tests to a normal file. e. Number of iterations of tests can be specified. The testsuite comes with its own configuration file "libsysfs.conf" in the "test" directory. This file is used to generate a header file at the time the tests are built. To use the testsuite: a. Modify the variables libsysfs.conf file to appropriate values for your system. (The libsysfs.conf file contains comments describing what each variable stands for and, in some cases, how to determine an appropriate value for the system under test). b. Build testsuite. c. Run the testsuite: testlibsysfs <number of iterations> <logfile> The default logfile is stdout. NOTE: If the libsysfs.conf file is changed, make sure to run "make clean" in the test directory and then a "make" for the changes to take effect. 10. Conclusion -------------- Libsysfs is meant to provide a stable application programming interface to sysfs. Applications can depend upon the library to access system devices and functions exposed through sysfs.
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