[libudev] 함수정리

libudev Reference Manual 참고

 

udev 

 

Manual 을 토대로 번역 하였음.

vim ./usr/include/libudev.h

DeskTop PC  ----$ udevd --version  

 204

다음과 같은 기능으로 나누어진다.

 

udev — libudev context

udev_list — list operation

udev_device — kernel sys devices

udev_monitor — device event source

udev_enumerate — lookup and sort sys devices

udev_queue — access to currently active events

udev_util — utils

 

---

 

udev -  udev 문맥에는 설정파읽을 읽은 기본값들이 들어있으며 모든라이브러리에 전달된다.

/*
 * udev - library context
 *
 * reads the udev config and system environment
 * allows custom logging
 */
 
struct udev;
 
struct udev *udev_ref(struct udev *udev);   // 객체를 제거 후 인자인 udev 를 반환. 일반적으로 udev_unref사용.
 
struct udev *udev_unref(struct udev *udev); //객체를 제거하며 NULL 반환 한다.
 
struct udev *udev_new(void);   //새로운 udev 객체를 할당하고 포인터를 반환한다. 성공시 컨텍스트 포인터 반환 실패시 NULL
 
void udev_set_log_fn(struct udev *udev,
 
                            void (*log_fn)(struct udev *udev,
 
                                           int priority, const char *file, int line, const char *fn,
 
                                           const char *format, va_list args));
// log_fn : 로그 표출할 함수 등록
 
int udev_get_log_priority(struct udev *udev); // 현재 로그 우선순위값 반환
 
void udev_set_log_priority(struct udev *udev, int priority); // 로그 우선순위 설정
 
void *udev_get_userdata(struct udev *udev);  //저장된 사용자 데이터 반환 (콜백 액세스 용도)
 
void udev_set_userdata(struct udev *udev, void *userdata);// 사용자 데이터 저장                    Colored by Color Scripter

/*
 * udev_list
 *
 * access to libudev generated lists
 */
struct udev_list_entry;
struct udev_list_entry *udev_list_entry_get_next(struct udev_list_entry *list_entry); //현재 리스트 값을 인자로 사용, return 다음 리스트 ,NULL 일시 다음 엔트리 X
struct udev_list_entry *udev_list_entry_get_by_name(struct udev_list_entry *list_entry, const char *name);  // name 과 일치하는 값을 반환 , NULL 반환시 X
const char *udev_list_entry_get_name(struct udev_list_entry *list_entry); // 해당 엔트리의 이름 반환
const char *udev_list_entry_get_value(struct udev_list_entry *list_entry); // 해당 엔트리의 스트링값 반환
 
/**
 * udev_list_entry_foreach:
 * @list_entry: entry to store the current position
 * @first_entry: first entry to start with
 *
 * Helper to iterate over all entries of a list.
 */
#define udev_list_entry_foreach(list_entry, first_entry) \   //list_entry : 현재 값을 저장 , first_entry : 시작값
        for (list_entry = first_entry; \
             list_entry != NULL; \
             list_entry = udev_list_entry_get_next(list_entry))
 

udev_device

 커널 sys 장치들을 나타낸다. 커널의 sys 장치들을 syspath 에 의해 고유하게 식별된다. 

/*
 * udev_device
 *
 * access to sysfs/kernel devices
 */
struct udev_device;
struct udev_device *udev_device_ref(struct udev_device *udev_device); // udev 장치대 대한 참조를 가져온다. 
struct udev_device *udev_device_unref(struct udev_device *udev_device); // 참조된 디바이스 해제, zero 리턴시 해제되었음을 알수 있다.
struct udev *udev_device_get_udev(struct udev_device *udev_device); // udev에 대한 정보를 획득
struct udev_device *udev_device_new_from_syspath(struct udev *udev, const char *syspath); // 새 udev 장치를 만들고sys 장치 및 udev 데이터 베이스 항목에 정보를 생성. 초기 refcount는 1이며 장치의 리소를
해제하기 위해 감소시켜야 한다. 새로운 udev 장치 Ehsms  존재하지 않는경우 NULL 반환 

struct udev_device *udev_device_new_from_devnum(struct udev *udev, char type, dev_t devnum);  // type: character or block, devnum : device major/ minor Number , return : 존재하지 않는 경우 NULL, 성공시 new udev device
struct udev_device *udev_device_new_from_subsystem_sysname(struct udev *udev, const char *subsystem, const char *sysname); //subsystem : like "mem" /"zero", "block" /"sda" , sysname:  디바이스이름 , Return : udev_device , 존재하지 않는경우 NULL
struct udev_device *udev_device_new_from_device_id(struct udev *udev, char *id);   
struct udev_device *udev_device_new_from_environment(struct udev *udev);
/* udev_device_get_parent_*() does not take a reference on the returned device, it is automatically unref'd with the parent */
struct udev_device *udev_device_get_parent(struct udev_device *udev_device);

/*
 서브시스템 및 디바이스 타입과 일치하는 장치를 검색 , devtype ="NULL" 일시 subsystem 함목만 검사 
 return : 일치하는 장치가 없는경우 NULL 반환
*/
struct udev_device *udev_device_get_parent_with_subsystem_devtype(struct udev_device *udev_device,
                                                                  const char *subsystem, const char *devtype);
/* retrieve device properties */
const char *udev_device_get_devpath(struct udev_device *udev_device);
const char *udev_device_get_subsystem(struct udev_device *udev_device);
const char *udev_device_get_devtype(struct udev_device *udev_device);
const char *udev_device_get_syspath(struct udev_device *udev_device);
const char *udev_device_get_sysname(struct udev_device *udev_device);
const char *udev_device_get_sysnum(struct udev_device *udev_device);
const char *udev_device_get_devnode(struct udev_device *udev_device);
int udev_device_get_is_initialized(struct udev_device *udev_device);
struct udev_list_entry *udev_device_get_devlinks_list_entry(struct udev_device *udev_device);
struct udev_list_entry *udev_device_get_properties_list_entry(struct udev_device *udev_device);
struct udev_list_entry *udev_device_get_tags_list_entry(struct udev_device *udev_device);
struct udev_list_entry *udev_device_get_sysattr_list_entry(struct udev_device *udev_device);
const char *udev_device_get_property_value(struct udev_device *udev_device, const char *key);
const char *udev_device_get_driver(struct udev_device *udev_device);
dev_t udev_device_get_devnum(struct udev_device *udev_device);
const char *udev_device_get_action(struct udev_device *udev_device);
unsigned long long int udev_device_get_seqnum(struct udev_device *udev_device);
unsigned long long int udev_device_get_usec_since_initialized(struct udev_device *udev_device);

// 속성값을 가져온다. return : sys 속성파일의 내용, 속성 값이 없으면 NULL
const char *udev_device_get_sysattr_value(struct udev_device *udev_device, const char *sysattr);
int udev_device_set_sysattr_value(struct udev_device *udev_device, const char *sysattr, char *value);
int udev_device_has_tag(struct udev_device *udev_device, const char *tag);

/*
 * udev_monitor
 *
 * access to kernel uevents and udev events
 */
struct udev_monitor;  // 이벤트 소스를 처리하는 객체
struct udev_monitor *udev_monitor_ref(struct udev_monitor *udev_monitor); 
struct udev_monitor *udev_monitor_unref(struct udev_monitor *udev_monitor); // destroy the udev monitor
struct udev *udev_monitor_get_udev(struct udev_monitor *udev_monitor); // monitor 가 참조한 udev 가져오기

/* kernel and udev generated events over netlink 
   udev : udev 객체
   name : 이벤트 소스 이름 ex)"udev"
   return : new udev monitor, NULL인경우 에러
*/
struct udev_monitor *udev_monitor_new_from_netlink(struct udev *udev, const char *name);

/* bind socket
  retrun: 0=success , -1 error
 */
int udev_monitor_enable_receiving(struct udev_monitor *udev_monitor);
int udev_monitor_set_receive_buffer_size(struct udev_monitor *udev_monitor, int size);

// udev_monitor 에 대한 파일디스크립터를 반환
int udev_monitor_get_fd(struct udev_monitor *udev_monitor);
struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monitor);

/* in-kernel socket filters to select messages that get delivered to a listener 
 모니터링 할 subsystem 과 devtype 을 등록한다. 
 return : 0= Success , 음수값 오류
*/
int udev_monitor_filter_add_match_subsystem_devtype(struct udev_monitor *udev_monitor,
                                                    const char *subsystem, const char *devtype);
int udev_monitor_filter_add_match_tag(struct udev_monitor *udev_monitor, const char *tag);
int udev_monitor_filter_update(struct udev_monitor *udev_monitor);
int udev_monitor_filter_remove(struct udev_monitor *udev_monitor);

udev_enumerate - sys 장치를 조회 및 정렬한다.

/*
 * udev_enumerate
 *
 * search sysfs for specific devices and provide a sorted list
 */
struct udev_enumerate;
struct udev_enumerate *udev_enumerate_ref(struct udev_enumerate *udev_enumerate);
struct udev_enumerate *udev_enumerate_unref(struct udev_enumerate *udev_enumerate);
struct udev *udev_enumerate_get_udev(struct udev_enumerate *udev_enumerate);
struct udev_enumerate *udev_enumerate_new(struct udev *udev);
/* device properties filter */
int udev_enumerate_add_match_subsystem(struct udev_enumerate *udev_enumerate, const char *subsystem); // 항목에 포함할 필터를 등록 0리턴시 성공
int udev_enumerate_add_nomatch_subsystem(struct udev_enumerate *udev_enumerate, const char *subsystem);
int udev_enumerate_add_match_sysattr(struct udev_enumerate *udev_enumerate, const char *sysattr, const char *value);
int udev_enumerate_add_nomatch_sysattr(struct udev_enumerate *udev_enumerate, const char *sysattr, const char *value);

/* 목록에 포함시킬 속성 필터를 등록한다. 
   property : 해당 속성
   value : 값
   return: 0= Success, - Fail
*/
int udev_enumerate_add_match_property(struct udev_enumerate *udev_enumerate, const char *property, const char *value);
int udev_enumerate_add_match_sysname(struct udev_enumerate *udev_enumerate, const char *sysname);
int udev_enumerate_add_match_tag(struct udev_enumerate *udev_enumerate, const char *tag);
int udev_enumerate_add_match_parent(struct udev_enumerate *udev_enumerate, struct udev_device *parent);
int udev_enumerate_add_match_is_initialized(struct udev_enumerate *udev_enumerate);
int udev_enumerate_add_syspath(struct udev_enumerate *udev_enumerate, const char *syspath);
/* run enumeration with active filters */
int udev_enumerate_scan_devices(struct udev_enumerate *udev_enumerate);  // return= 0 Success, - Fail
int udev_enumerate_scan_subsystems(struct udev_enumerate *udev_enumerate);
/* return device list */
struct udev_list_entry *udev_enumerate_get_list_entry(struct udev_enumerate *udev_enumerate);

/*
 * udev_queue
 *
 * access to the currently running udev events
 */
struct udev_queue;
struct udev_queue *udev_queue_ref(struct udev_queue *udev_queue);
struct udev_queue *udev_queue_unref(struct udev_queue *udev_queue);
struct udev *udev_queue_get_udev(struct udev_queue *udev_queue);
struct udev_queue *udev_queue_new(struct udev *udev);
unsigned long long int udev_queue_get_kernel_seqnum(struct udev_queue *udev_queue);
unsigned long long int udev_queue_get_udev_seqnum(struct udev_queue *udev_queue);
int udev_queue_get_udev_is_active(struct udev_queue *udev_queue);
int udev_queue_get_queue_is_empty(struct udev_queue *udev_queue);
int udev_queue_get_seqnum_is_finished(struct udev_queue *udev_queue, unsigned long long int seqnum);
int udev_queue_get_seqnum_sequence_is_finished(struct udev_queue *udev_queue,
                                               unsigned long long int start, unsigned long long int end);
struct udev_list_entry *udev_queue_get_queued_list_entry(struct udev_queue *udev_queue);
 

/*
 *  udev_hwdb
 *
 *  access to the static hardware properties database
 */
struct udev_hwdb;
struct udev_hwdb *udev_hwdb_new(struct udev *udev);
struct udev_hwdb *udev_hwdb_ref(struct udev_hwdb *hwdb);
struct udev_hwdb *udev_hwdb_unref(struct udev_hwdb *hwdb);
struct udev_list_entry *udev_hwdb_get_properties_list_entry(struct udev_hwdb *hwdb, const char *modalias, unsigned int flags);

/*
 * udev_util
 *
 * udev specific utilities
 */
int udev_util_encode_string(const char *str, char *str_enc, size_t len);
 

참고사이트

  libudev Reference Manual: https://www.kernel.org/pub/linux/utils/kernel/hotplug/libudev/ch01.html