247 lines
7.0 KiB
Groff
247 lines
7.0 KiB
Groff
.\" $NetBSD: kprintf.9,v 1.7 1999/09/12 18:47:13 kleink Exp $
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.\"
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.\" Copyright (c) 1998 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jeremy Cooper.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd September 1, 1998
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.Dt KPRINTF 9
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.Os
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.Sh NAME
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.Nm printf, sprintf, vprintf, uprintf, ttyprintf
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.Nd kernel formatted output conversion
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.Sh SYNOPSIS
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.Fd #include <sys/systm.h>
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.Ft void
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.Fo "printf"
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.Fa "const char *format"
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.Fa "..."
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.Fc
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.Ft int
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.Fo "sprintf"
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.Fa "char *buf"
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.Fa "const char *format"
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.Fa "..."
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.Fc
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.Ft void
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.Fo "vprintf"
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.Fa "const char *format"
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.Fa "va_list ap"
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.Fc
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.Ft void
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.Fo "uprintf"
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.Fa "const char *format"
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.Fa "..."
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.Fc
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.Ft void
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.Fo "ttyprintf"
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.Fa "struct tty *tty"
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.Fa "const char *format"
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.Fa "..."
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.Fc
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.Sh DESCRIPTION
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The
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.Fn printf ,
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.Fn sprintf ,
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.Fn vprintf ,
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.Fn uprintf ,
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and
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.Fn ttyprintf
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functions allow the kernel to send formatted messages to various output
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devices.
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The functions
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.Fn printf
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and
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.Fn vprintf
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send formatted strings to the system console.
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The functions
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.Fn uprintf
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and
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.Fn ttyprintf
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send formatted strings to the current process's controlling tty and a specific
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tty,
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respectively.
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.Pp
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Since each of these kernel functions is a scaled down version of its user space
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counterpart
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.Po
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.Xr printf 3 ,
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.Xr sprintf 3 ,
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and
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.Xr vprintf 3
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.Pc ,
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this page describes only the differences between the user space and kernel
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versions, rather than describing all of their functional details.
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.Ss FORMAT OPTIONS
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In addition to the formatting specifiers that the user space functions
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accept in the format string
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.Fa format ,
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the kernel functions accept the following format specifiers.
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.Pp
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.Bl -tag -width "\e177"
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.It Li %b
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Bit field expansion.
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This format specifier is useful for decoding bit fields in device registers.
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It displays an integer using a specified radix
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.Pq base
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and an interpretation of
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the bits within that integer as though they were flags.
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It requires two arguments from the argument vector, the first argument being
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the bit field to be decoded
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.Pq "as an integer"
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and the second being a decoding directive string.
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.Pp
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The decoding directive string describes how the bitfield is to be interpreted
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and displayed.
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The first character of the string is a binary character representation of the
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output numeral base in which the bitfield will be printed before it is decoded.
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Recognized radix values
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.Pq "in C escape-character format"
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are
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.Li \e10
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.Pq octal ,
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.Li \e12
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.Pq decimal ,
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and
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.Li \e20
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.Pq hexadecimal .
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.Pp
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The remaining characters in the decoding directive string are interpreted as a
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list of bit-position\(endescription pairs.
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A bit-position\(endescription pair begins with a binary character value
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that represents the position of the bit being described.
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A bit position value of one describes the least significant bit.
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Whereas a position value of 32
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.Pq "octal 40, hexadecimal 20, the ASCII space character"
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describes the most significant bit.
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.Pp
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The remaining characters in a bit-position\(endescription pair are the
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characters to print should the bit being described be set.
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Description strings are delimited by the next bit position value character
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encountered
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.Pq "distinguishable by its value being \(<= 32" ,
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or the end of the decoding directive string itself.
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.It Li %:
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Inline format continuation.
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This format specifier allows for recursive formatted output.
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Its argument is the new formatting string to obey and the argument which
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follows it is a
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.Va va_list
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argument vector from which to obtain the data to be formatted.
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.It Li %r
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Integer value using current
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.Tn DDB
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radix.
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.Bf -emphasis
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This format specifier is only availble in kernels enabled with the
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.Tn DDB
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debugger.
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.Po
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See
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.Xr ddb 4
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.Pc .
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.Ef
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Displays an integer using the current
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.Tn DDB
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radix.
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.It Li %z
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Signed hexadecimal with
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.Ql 0x
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prefix.
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.Bf -emphasis
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This format specifier is only available in kernels enabled with the
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.Tn DDB
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debugger.
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.Po
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See
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.Xr ddb 4
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.Pc .
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.Ef
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Displays a signed integer using the C-style hexadecimal constant format.
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.El
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.Sh RETURN VALUES
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The
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.Fn sprintf
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function returns the number of characters it placed in the buffer
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.Fa buf .
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.Sh EXAMPLES
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An example use of the
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.Li %b
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format specifier for decoding device registers.
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.Bd -literal -offset indent
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printf("reg=%b\en", 3, "\e10\e2BITTWO\e1BITONE")
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\(rA "reg=3<BITTWO,BITONE>"
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printf("enablereg=%b\en", 0xe860,
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"\e20\ex10NOTBOOT\ex0fFPP\ex0eSDVMA\ex0cVIDEO"
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"\ex0bLORES\ex0aFPA\ex09DIAG\ex07CACHE"
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"\ex06IOCACHE\ex05LOOPBACK\ex04DBGCACHE")
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\(rA "enablereg=e860<NOTBOOT,FPP,SDVMA,VIDEO,CACHE,IOCACHE>"
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.Ed
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.Pp
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An example use of the
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.Li %:
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format specifier for recursive formatting.
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.Bd -literal -offset indent
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void
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bail(char *fmt, ...)
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{
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va_list ap;
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va_start (ap, fmt);
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printf("bailing out: %:\en", fmt, ap);
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va_end(ap);
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}
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bail("descriptor %d is invalid.", 5)
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\(rA "bailing out: descriptor 5 is invalid"
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.Ed
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.Sh SEE ALSO
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.\" The following page has not been written, but I am including a cross-
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.\" reference to it in the hopes that it will inspire someone to write it.
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.Xr printf 3 ,
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.Xr printf 1 ,
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.Xr ddb 4 ,
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.Xr tprintf 9
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.Sh CODE REFERENCES
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.Pa sys/kern/subr_prf.c
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.Sh BUGS
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The
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.Li %b
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format specifier cannot be used to decode integers greater than 32 bits in
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size.
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The
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.Fn uprintf
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and
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.Fn ttyprintf
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functions should be used sparingly, if at all.
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