lis_register_strdev.9

7号信令功能代码,为开源代码

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.TH LIS_REGISTER_STRDEV 9 "2004/01/12 23:33:06" "LiS-2_16_18-8" "Linux STREAMS DDI/DKI"
.SH NAME
.B lis_register_strdev
\- register a \fISTREAMS\fR device
.SH SYNOPSIS
.PP
.B #include <sys/stream.h>
.HP 8
.BI "int " retval " = lis_register_strdev(major_t " major ", struct streamtab *" strtab ", int " nminor ", const char *" name );
.SH DESCRIPTION
.PP
.BR lis_register_strdev ()
allocates a major device number and
registers a new
.IR STREAMS (4)
device with the
.B Linux
kernel against that major device
number.
Once a
.IR STREAMS (4)
device is registered, opening a device with the registered major device number
will result in a call to the
.IR STREAMS (4)
driver's open routine.
.PP
.BR lis_register_strdev ()
is an LiS-specific function.
.[
LiS
.]
.IR STREAMS (4)
devices registered with
.BR lis_register_strdev ()
can be deregistered with
.BR lis_unregister_strdev (9).
.PP
.BR lis_register_strdev ()
registers the
.IR STREAMS (4)
device with the
.B streamtab
structure pointed to by
.I strtab
and the name pointed to by
.IR name .
When
.I major
is specified as zero (0),
.BR lis_register_strdev ()
will attempt to assign a major device number to the device.
When
.I major
is non-zero,
.BR lis_regsiter_strdev ()
will attempt to use the major device number specified by
.IR major .
.PP
.BR lis_register_strdev ()
uses the
.B Linux
kernel function
.BR register_chrdev ()
to register the character special device.
.PP
.BR lis_register_strdev ()
ignores the
.I nminor
argument.  This argument used to allocate a range of minors in previous
versions of LiS,
.[
LiS
.]
but is no longer used.
.SS "Linux Kernel Module Loading"
.PP
.B Linux
has the feature that if a character major device is unassigned and an attempt
is made to open a character device with the major device number, the
.B Linux
kernel will attempt to load the kernel module
\fB\)char-major-\fI\)XXX\fR\),
where
.I XXX
is the ascii major device number.
.PP
This is a feature of
.B Linux
and is not specific to
.B LiS\c
.
.[
LiS
.]
.SH "RETURN VALUES"
.PP
Upon success,
.BR lis_register_strdev ()
returns a positive integer representing the major device number assigned to
the
.IR STREAMS (4)
device.
.PP
Upon failure,
.BR lis_register_strdev ()
returns a negative error number.
.SH ERRORS
.PP
When
.BR lis_regsister_strdev ()
fails it returns the negative of one of the following errors:
.TP
.RB [ EIO ]
The device major number specified by
.I major
could not be assigned; or, if
.I major
was zero, a new major device number could not be assigned.
.TP
.RB [ EINVAL ]
The
.B streamtab
pointer
.I strtab
is
.BR NULL .
.TP
.RB [ EBUSY ]
The specified major device number is already in use by another
.IR STREAMS (4)
character special device.
.SH CAVEATS
.PP
.B LiS
.[
LiS
.]
uses a fixed size switch table to contain registered devices.
is 
.SH EXAMPLES
.PP
The following example demonstrates how 4 major device numbers could be
registered against a
.IR STREAMS (4)
driver:
.sp
.in +4
.nf
\fC\s-2\
#define X_MAJOR 222
#define X_NMAJOR 4
#define X_NMINOR 255
#define X_DRV_NAME "example"

int x_initialized = 0;
ushort x_majors[X_NMAJOR] = { X_CMAJOR, };

void x_init(void)
{
    int err, mindex;
    for (mindex = 0; mindex < X_NMAJOR; mindex++) {
	if ((err = lis_register_strdev(x_majors[mindex], &x_info,
				       X_NMINOR, X_DRV_NAME)) < 0) {
	    if (!mindex) {
		cmn_err(CE_PANIC,
			"%s: could not register 1'st major %d",
			X_DRV_NAME, x_majors[mindex]);
		x_initialized = err;
		return;
	    }
	    cmn_err(CE_WARN, "%s: could not register %d'th major",
		    X_DRV_NAME, mindex + 1);
	    x_majors[mindex] = 0;
	} else if (mindex)
	    x_majors[mindex] = err;
    }
    x_initialized = 1;
    return;
}

void x_terminate(void)
{
    int err, mindex;
    for (mindex = 0; mindex < X_NMAJOR; mindex++) {
	if (x_majors[mindex]) {
	    if ((err = lis_unregister_strdev(x_majors[mindex])))
		cmn_err(CE_PANIC, "%s: could not unregister major %d",
			X_DRV_NAME, x_majors[mindex]);
	    if (mindex)
		x_majors[mindex] = 0;
	}
    }
    return;
}
\s+2\fR
.fi
.PP
Where the example above is compiled into a
.B Linux
kernel module named
\fB\)streams-\fI\)x\fB\).o\fR\),
placing a line such as follows in the
.BR /etc/modules.conf " or " /etc/conf.modules
file will cause the
.B Linux
kernel to load the streams module on demand.
.sp
.in +4
.nf
\fC\s-2\
alias char-major-222 streams-x  # demand load streams device x
\s+2\fR
.fi

.B 
.SH FILES
.B /etc/conf.modules
.br
.B /etc/modules.conf
.SH "SEE ALSO"
.PP
.BR lis_register_strmod (9),
.BR lis_unregister_strdev (9),
.BR lis_unregister_strmod (9).
.\"
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