These functions handle file descriptor owner related ioctls and related signal delivery. Device drivers and other parts of the kernel call these functions from ioctl entry functions or I/O notification functions.
fsetown() sets the owner of file.
cmd is an ioctl command, one of
SIOCSPGRP,
FIOSETOWN, and
TIOCSPGRP.
data is interpreted as a pointer to a signed integer, the integer being the ID of the owner. The
cmd determines how exactly
data should be interpreted. If
cmd is
TIOCSPGRP, the ID needs to be positive and is interpreted as process group ID. For
SIOCSPGRP and
FIOSETOWN, the passed ID is the process ID if positive, or the process group ID if negative.
fgetown() returns the current owner of the file.
cmd is an ioctl command, one of
SIOCGPGRP,
FIOGETOWN, and
TIOCGPGRP.
data is interpreted as a pointer to a signed integer, and the value is set according to the passed
cmd. For
TIOCGPGRP, the returned
data value is positive process group ID if the owner is the process group, or negative process ID if the owner is a process. For other ioctls, the returned value is the positive process ID if the owner is a process, or the negative process group ID if the owner is a process group.
fownsignal() schedules the
signo signal to be sent to the current file descriptor owner. The signals typically used with this function are
SIGIO and
SIGURG. The
code and
band arguments are sent along with the signal as additional signal specific information if
SA_SIGINFO is activated. If the information is not available from the context of the
fownsignal() call, these should be passed as zero.
fdescdata is used to lookup the file descriptor for
SA_SIGINFO signals. If it is specified, the file descriptor number is sent along with the signal as additional signal specific information. If file descriptor data pointer is not available in the context of the
fownsignal() call,
NULL should be used instead.
Note that a
fcntl(2) F_SETOWN request is translated by the kernel to a
FIOSETOWN ioctl, and
F_GETOWN is translated to
FIOGETOWN. This is done transparently by generic code, before the device- or subsystem-specific ioctl entry function is called.