UDEV_DEVICE_NEW_FROM_SYSPudev3device_new_from_sUDEVtDEVICE_NEW_FROM_SYSPATH(3)
NAME
udev_device_new_from_syspath, udev_device_new_from_devnum,
udev_device_new_from_subsystem_sysname, udev_device_new_from_device_id,
udev_device_new_from_environment, udev_device_ref, udev_device_unref -
Create, acquire and release a udev device object
SYNOPSIS
#include <libudev.h>
struct udev_device *udev_device_new_from_syspath(struct udev *udev,
const char *syspath);
struct udev_device *udev_device_new_from_devnum(struct udev *udev,
char type,
dev_t devnum);
struct udev_device
*udev_device_new_from_subsystem_sysname(struct udev *udev,
const char *subsystem,
const char *sysname);
struct udev_device *udev_device_new_from_device_id(struct udev *udev,
const char *id);
struct udev_device
*udev_device_new_from_environment(struct udev *udev);
struct udev_device *udev_device_ref(struct udev_device *udev_device);
struct udev_device *udev_device_unref(struct udev_device *udev_device);
DESCRIPTION
udev_device_new_from_syspath(), udev_device_new_from_devnum(),
udev_device_new_from_subsystem_sysname(),
udev_device_new_from_device_id(), and
udev_device_new_from_environment() allocate a new udev device object
and returns a pointer to it. This object is opaque and must not be
accessed by the caller via different means than functions provided by
libudev. Initially, the reference count of the device is 1. You can
acquire further references, and drop gained references via
udev_device_ref() and udev_device_unref(). Once the reference count
hits 0, the device object is destroyed and freed.
udev_device_new_from_syspath(), udev_device_new_from_devnum(),
udev_device_new_from_subsystem_sysname(), and
udev_device_new_from_device_id() create the device object based on
information found in /sys/, annotated with properties from the
udev-internal device database. A syspath is any subdirectory of /sys/,
with the restriction that a subdirectory of /sys/devices (or a symlink
to one) represents a real device and as such must contain a uevent
file. udev_device_new_from_devnum() takes a device type, which can be
b for block devices or c for character devices, as well as a devnum
(see makedev(3)). udev_device_new_from_subsystem_sysname() looks up
devices based on the provided subsystem and sysname (see
udev_device_get_subsystem(3) and udev_device_get_sysname(3)) and
udev_device_new_from_device_id() looks up devices based on the provided
device ID, which is a special string in one of the following four
forms:
Table 1. Device ID strings
┌──────────────┬──────────────────────────┐
│Example │ Explanation │
├──────────────┼──────────────────────────┤
│b8:2 │ block device major:minor │
├──────────────┼──────────────────────────┤
│c128:1 │ char device major:minor │
├──────────────┼──────────────────────────┤
│n3 │ network device ifindex │
├──────────────┼──────────────────────────┤
│+sound:card29 │ kernel driver core │
│ │ subsystem:device name │
└──────────────┴──────────────────────────┘
udev_device_new_from_environment() creates a device from the current
environment (see environ(7)). Each key-value pair is interpreted in the
same way as if it was received in an uevent (see
udev_monitor_receive_device(3)). The keys DEVPATH, SUBSYSTEM, ACTION,
and SEQNUM are mandatory.
RETURN VALUE
On success, udev_device_new_from_syspath(),
udev_device_new_from_devnum(),
udev_device_new_from_subsystem_sysname(),
udev_device_new_from_device_id() and udev_device_new_from_environment()
return a pointer to the allocated udev device. On failure, NULL is
returned, and errno is set appropriately. udev_device_ref() returns
the argument that it was passed, unmodified. udev_device_unref()
always returns NULL.
SEE ALSO
udev_new(3), udev_device_get_syspath(3), udev_device_has_tag(3),
udev_enumerate_new(3), udev_monitor_new_from_netlink(3),
udev_list_entry(3), systemd(1),
systemd 252 UDEV_DEVICE_NEW_FROM_SYSPATH(3)
Generated by dwww version 1.15 on Wed Jun 26 18:06:09 CEST 2024.