mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-12 23:33:55 +08:00
58235413b2
librs docbook typo fixes. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
290 lines
8.0 KiB
XML
290 lines
8.0 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
|
|
|
|
<book id="Reed-Solomon-Library-Guide">
|
|
<bookinfo>
|
|
<title>Reed-Solomon Library Programming Interface</title>
|
|
|
|
<authorgroup>
|
|
<author>
|
|
<firstname>Thomas</firstname>
|
|
<surname>Gleixner</surname>
|
|
<affiliation>
|
|
<address>
|
|
<email>tglx@linutronix.de</email>
|
|
</address>
|
|
</affiliation>
|
|
</author>
|
|
</authorgroup>
|
|
|
|
<copyright>
|
|
<year>2004</year>
|
|
<holder>Thomas Gleixner</holder>
|
|
</copyright>
|
|
|
|
<legalnotice>
|
|
<para>
|
|
This documentation is free software; you can redistribute
|
|
it and/or modify it under the terms of the GNU General Public
|
|
License version 2 as published by the Free Software Foundation.
|
|
</para>
|
|
|
|
<para>
|
|
This program is distributed in the hope that it will be
|
|
useful, but WITHOUT ANY WARRANTY; without even the implied
|
|
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
|
|
See the GNU General Public License for more details.
|
|
</para>
|
|
|
|
<para>
|
|
You should have received a copy of the GNU General Public
|
|
License along with this program; if not, write to the Free
|
|
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
|
|
MA 02111-1307 USA
|
|
</para>
|
|
|
|
<para>
|
|
For more details see the file COPYING in the source
|
|
distribution of Linux.
|
|
</para>
|
|
</legalnotice>
|
|
</bookinfo>
|
|
|
|
<toc></toc>
|
|
|
|
<chapter id="intro">
|
|
<title>Introduction</title>
|
|
<para>
|
|
The generic Reed-Solomon Library provides encoding, decoding
|
|
and error correction functions.
|
|
</para>
|
|
<para>
|
|
Reed-Solomon codes are used in communication and storage
|
|
applications to ensure data integrity.
|
|
</para>
|
|
<para>
|
|
This documentation is provided for developers who want to utilize
|
|
the functions provided by the library.
|
|
</para>
|
|
</chapter>
|
|
|
|
<chapter id="bugs">
|
|
<title>Known Bugs And Assumptions</title>
|
|
<para>
|
|
None.
|
|
</para>
|
|
</chapter>
|
|
|
|
<chapter id="usage">
|
|
<title>Usage</title>
|
|
<para>
|
|
This chapter provides examples of how to use the library.
|
|
</para>
|
|
<sect1>
|
|
<title>Initializing</title>
|
|
<para>
|
|
The init function init_rs returns a pointer to an
|
|
rs decoder structure, which holds the necessary
|
|
information for encoding, decoding and error correction
|
|
with the given polynomial. It either uses an existing
|
|
matching decoder or creates a new one. On creation all
|
|
the lookup tables for fast en/decoding are created.
|
|
The function may take a while, so make sure not to
|
|
call it in critical code paths.
|
|
</para>
|
|
<programlisting>
|
|
/* the Reed Solomon control structure */
|
|
static struct rs_control *rs_decoder;
|
|
|
|
/* Symbolsize is 10 (bits)
|
|
* Primitive polynomial is x^10+x^3+1
|
|
* first consecutive root is 0
|
|
* primitive element to generate roots = 1
|
|
* generator polynomial degree (number of roots) = 6
|
|
*/
|
|
rs_decoder = init_rs (10, 0x409, 0, 1, 6);
|
|
</programlisting>
|
|
</sect1>
|
|
<sect1>
|
|
<title>Encoding</title>
|
|
<para>
|
|
The encoder calculates the Reed-Solomon code over
|
|
the given data length and stores the result in
|
|
the parity buffer. Note that the parity buffer must
|
|
be initialized before calling the encoder.
|
|
</para>
|
|
<para>
|
|
The expanded data can be inverted on the fly by
|
|
providing a non-zero inversion mask. The expanded data is
|
|
XOR'ed with the mask. This is used e.g. for FLASH
|
|
ECC, where the all 0xFF is inverted to an all 0x00.
|
|
The Reed-Solomon code for all 0x00 is all 0x00. The
|
|
code is inverted before storing to FLASH so it is 0xFF
|
|
too. This prevents that reading from an erased FLASH
|
|
results in ECC errors.
|
|
</para>
|
|
<para>
|
|
The databytes are expanded to the given symbol size
|
|
on the fly. There is no support for encoding continuous
|
|
bitstreams with a symbol size != 8 at the moment. If
|
|
it is necessary it should be not a big deal to implement
|
|
such functionality.
|
|
</para>
|
|
<programlisting>
|
|
/* Parity buffer. Size = number of roots */
|
|
uint16_t par[6];
|
|
/* Initialize the parity buffer */
|
|
memset(par, 0, sizeof(par));
|
|
/* Encode 512 byte in data8. Store parity in buffer par */
|
|
encode_rs8 (rs_decoder, data8, 512, par, 0);
|
|
</programlisting>
|
|
</sect1>
|
|
<sect1>
|
|
<title>Decoding</title>
|
|
<para>
|
|
The decoder calculates the syndrome over
|
|
the given data length and the received parity symbols
|
|
and corrects errors in the data.
|
|
</para>
|
|
<para>
|
|
If a syndrome is available from a hardware decoder
|
|
then the syndrome calculation is skipped.
|
|
</para>
|
|
<para>
|
|
The correction of the data buffer can be suppressed
|
|
by providing a correction pattern buffer and an error
|
|
location buffer to the decoder. The decoder stores the
|
|
calculated error location and the correction bitmask
|
|
in the given buffers. This is useful for hardware
|
|
decoders which use a weird bit ordering scheme.
|
|
</para>
|
|
<para>
|
|
The databytes are expanded to the given symbol size
|
|
on the fly. There is no support for decoding continuous
|
|
bitstreams with a symbolsize != 8 at the moment. If
|
|
it is necessary it should be not a big deal to implement
|
|
such functionality.
|
|
</para>
|
|
|
|
<sect2>
|
|
<title>
|
|
Decoding with syndrome calculation, direct data correction
|
|
</title>
|
|
<programlisting>
|
|
/* Parity buffer. Size = number of roots */
|
|
uint16_t par[6];
|
|
uint8_t data[512];
|
|
int numerr;
|
|
/* Receive data */
|
|
.....
|
|
/* Receive parity */
|
|
.....
|
|
/* Decode 512 byte in data8.*/
|
|
numerr = decode_rs8 (rs_decoder, data8, par, 512, NULL, 0, NULL, 0, NULL);
|
|
</programlisting>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>
|
|
Decoding with syndrome given by hardware decoder, direct data correction
|
|
</title>
|
|
<programlisting>
|
|
/* Parity buffer. Size = number of roots */
|
|
uint16_t par[6], syn[6];
|
|
uint8_t data[512];
|
|
int numerr;
|
|
/* Receive data */
|
|
.....
|
|
/* Receive parity */
|
|
.....
|
|
/* Get syndrome from hardware decoder */
|
|
.....
|
|
/* Decode 512 byte in data8.*/
|
|
numerr = decode_rs8 (rs_decoder, data8, par, 512, syn, 0, NULL, 0, NULL);
|
|
</programlisting>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>
|
|
Decoding with syndrome given by hardware decoder, no direct data correction.
|
|
</title>
|
|
<para>
|
|
Note: It's not necessary to give data and received parity to the decoder.
|
|
</para>
|
|
<programlisting>
|
|
/* Parity buffer. Size = number of roots */
|
|
uint16_t par[6], syn[6], corr[8];
|
|
uint8_t data[512];
|
|
int numerr, errpos[8];
|
|
/* Receive data */
|
|
.....
|
|
/* Receive parity */
|
|
.....
|
|
/* Get syndrome from hardware decoder */
|
|
.....
|
|
/* Decode 512 byte in data8.*/
|
|
numerr = decode_rs8 (rs_decoder, NULL, NULL, 512, syn, 0, errpos, 0, corr);
|
|
for (i = 0; i < numerr; i++) {
|
|
do_error_correction_in_your_buffer(errpos[i], corr[i]);
|
|
}
|
|
</programlisting>
|
|
</sect2>
|
|
</sect1>
|
|
<sect1>
|
|
<title>Cleanup</title>
|
|
<para>
|
|
The function free_rs frees the allocated resources,
|
|
if the caller is the last user of the decoder.
|
|
</para>
|
|
<programlisting>
|
|
/* Release resources */
|
|
free_rs(rs_decoder);
|
|
</programlisting>
|
|
</sect1>
|
|
|
|
</chapter>
|
|
|
|
<chapter id="structs">
|
|
<title>Structures</title>
|
|
<para>
|
|
This chapter contains the autogenerated documentation of the structures which are
|
|
used in the Reed-Solomon Library and are relevant for a developer.
|
|
</para>
|
|
!Iinclude/linux/rslib.h
|
|
</chapter>
|
|
|
|
<chapter id="pubfunctions">
|
|
<title>Public Functions Provided</title>
|
|
<para>
|
|
This chapter contains the autogenerated documentation of the Reed-Solomon functions
|
|
which are exported.
|
|
</para>
|
|
!Elib/reed_solomon/reed_solomon.c
|
|
</chapter>
|
|
|
|
<chapter id="credits">
|
|
<title>Credits</title>
|
|
<para>
|
|
The library code for encoding and decoding was written by Phil Karn.
|
|
</para>
|
|
<programlisting>
|
|
Copyright 2002, Phil Karn, KA9Q
|
|
May be used under the terms of the GNU General Public License (GPL)
|
|
</programlisting>
|
|
<para>
|
|
The wrapper functions and interfaces are written by Thomas Gleixner.
|
|
</para>
|
|
<para>
|
|
Many users have provided bugfixes, improvements and helping hands for testing.
|
|
Thanks a lot.
|
|
</para>
|
|
<para>
|
|
The following people have contributed to this document:
|
|
</para>
|
|
<para>
|
|
Thomas Gleixner<email>tglx@linutronix.de</email>
|
|
</para>
|
|
</chapter>
|
|
</book>
|