forked from Minki/linux
docs-rst: convert librs book to ReST
Use pandoc to convert documentation to ReST by calling Documentation/sphinx/tmplcvt script. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
This commit is contained in:
Mauro Carvalho Chehab
parent
e85ca0a31f
commit
8aba784832
@ -8,7 +8,7 @@
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DOCBOOKS := \
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lsm.xml \
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mtdnand.xml librs.xml \
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mtdnand.xml \
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sh.xml
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ifeq ($(DOCBOOKS),)
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@ -1,289 +0,0 @@
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
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<book id="Reed-Solomon-Library-Guide">
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<bookinfo>
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<title>Reed-Solomon Library Programming Interface</title>
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<authorgroup>
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<author>
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<firstname>Thomas</firstname>
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<surname>Gleixner</surname>
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<affiliation>
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<address>
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<email>tglx@linutronix.de</email>
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</address>
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</affiliation>
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</author>
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</authorgroup>
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<copyright>
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<year>2004</year>
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<holder>Thomas Gleixner</holder>
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</copyright>
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<legalnotice>
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<para>
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This documentation is free software; you can redistribute
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it and/or modify it under the terms of the GNU General Public
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License version 2 as published by the Free Software Foundation.
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</para>
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<para>
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This program is distributed in the hope that it will be
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useful, but WITHOUT ANY WARRANTY; without even the implied
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warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the GNU General Public License for more details.
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</para>
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<para>
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You should have received a copy of the GNU General Public
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License along with this program; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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MA 02111-1307 USA
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</para>
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<para>
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For more details see the file COPYING in the source
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distribution of Linux.
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</para>
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</legalnotice>
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</bookinfo>
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<toc></toc>
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<chapter id="intro">
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<title>Introduction</title>
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<para>
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The generic Reed-Solomon Library provides encoding, decoding
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and error correction functions.
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</para>
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<para>
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Reed-Solomon codes are used in communication and storage
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applications to ensure data integrity.
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</para>
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<para>
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This documentation is provided for developers who want to utilize
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the functions provided by the library.
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</para>
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</chapter>
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<chapter id="bugs">
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<title>Known Bugs And Assumptions</title>
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<para>
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None.
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</para>
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</chapter>
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<chapter id="usage">
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<title>Usage</title>
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<para>
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This chapter provides examples of how to use the library.
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</para>
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<sect1>
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<title>Initializing</title>
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<para>
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The init function init_rs returns a pointer to an
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rs decoder structure, which holds the necessary
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information for encoding, decoding and error correction
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with the given polynomial. It either uses an existing
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matching decoder or creates a new one. On creation all
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the lookup tables for fast en/decoding are created.
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The function may take a while, so make sure not to
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call it in critical code paths.
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</para>
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<programlisting>
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/* the Reed Solomon control structure */
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static struct rs_control *rs_decoder;
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/* Symbolsize is 10 (bits)
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* Primitive polynomial is x^10+x^3+1
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* first consecutive root is 0
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* primitive element to generate roots = 1
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* generator polynomial degree (number of roots) = 6
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*/
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rs_decoder = init_rs (10, 0x409, 0, 1, 6);
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</programlisting>
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</sect1>
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<sect1>
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<title>Encoding</title>
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<para>
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The encoder calculates the Reed-Solomon code over
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the given data length and stores the result in
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the parity buffer. Note that the parity buffer must
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be initialized before calling the encoder.
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</para>
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<para>
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The expanded data can be inverted on the fly by
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providing a non-zero inversion mask. The expanded data is
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XOR'ed with the mask. This is used e.g. for FLASH
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ECC, where the all 0xFF is inverted to an all 0x00.
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The Reed-Solomon code for all 0x00 is all 0x00. The
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code is inverted before storing to FLASH so it is 0xFF
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too. This prevents that reading from an erased FLASH
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results in ECC errors.
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</para>
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<para>
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The databytes are expanded to the given symbol size
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on the fly. There is no support for encoding continuous
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bitstreams with a symbol size != 8 at the moment. If
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it is necessary it should be not a big deal to implement
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such functionality.
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</para>
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<programlisting>
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/* Parity buffer. Size = number of roots */
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uint16_t par[6];
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/* Initialize the parity buffer */
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memset(par, 0, sizeof(par));
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/* Encode 512 byte in data8. Store parity in buffer par */
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encode_rs8 (rs_decoder, data8, 512, par, 0);
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</programlisting>
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</sect1>
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<sect1>
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<title>Decoding</title>
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<para>
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The decoder calculates the syndrome over
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the given data length and the received parity symbols
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and corrects errors in the data.
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</para>
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<para>
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If a syndrome is available from a hardware decoder
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then the syndrome calculation is skipped.
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</para>
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<para>
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The correction of the data buffer can be suppressed
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by providing a correction pattern buffer and an error
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location buffer to the decoder. The decoder stores the
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calculated error location and the correction bitmask
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in the given buffers. This is useful for hardware
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decoders which use a weird bit ordering scheme.
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</para>
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<para>
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The databytes are expanded to the given symbol size
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on the fly. There is no support for decoding continuous
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bitstreams with a symbolsize != 8 at the moment. If
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it is necessary it should be not a big deal to implement
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such functionality.
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</para>
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<sect2>
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<title>
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Decoding with syndrome calculation, direct data correction
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</title>
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<programlisting>
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/* Parity buffer. Size = number of roots */
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uint16_t par[6];
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uint8_t data[512];
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int numerr;
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/* Receive data */
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.....
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/* Receive parity */
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.....
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/* Decode 512 byte in data8.*/
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numerr = decode_rs8 (rs_decoder, data8, par, 512, NULL, 0, NULL, 0, NULL);
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</programlisting>
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</sect2>
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<sect2>
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<title>
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Decoding with syndrome given by hardware decoder, direct data correction
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</title>
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<programlisting>
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/* Parity buffer. Size = number of roots */
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uint16_t par[6], syn[6];
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uint8_t data[512];
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int numerr;
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/* Receive data */
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.....
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/* Receive parity */
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.....
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/* Get syndrome from hardware decoder */
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.....
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/* Decode 512 byte in data8.*/
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numerr = decode_rs8 (rs_decoder, data8, par, 512, syn, 0, NULL, 0, NULL);
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</programlisting>
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</sect2>
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<sect2>
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<title>
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Decoding with syndrome given by hardware decoder, no direct data correction.
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</title>
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<para>
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Note: It's not necessary to give data and received parity to the decoder.
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</para>
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<programlisting>
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/* Parity buffer. Size = number of roots */
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uint16_t par[6], syn[6], corr[8];
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uint8_t data[512];
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int numerr, errpos[8];
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/* Receive data */
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.....
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/* Receive parity */
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.....
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/* Get syndrome from hardware decoder */
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.....
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/* Decode 512 byte in data8.*/
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numerr = decode_rs8 (rs_decoder, NULL, NULL, 512, syn, 0, errpos, 0, corr);
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for (i = 0; i < numerr; i++) {
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do_error_correction_in_your_buffer(errpos[i], corr[i]);
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}
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</programlisting>
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</sect2>
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</sect1>
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<sect1>
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<title>Cleanup</title>
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<para>
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The function free_rs frees the allocated resources,
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if the caller is the last user of the decoder.
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</para>
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<programlisting>
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/* Release resources */
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free_rs(rs_decoder);
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</programlisting>
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</sect1>
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</chapter>
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<chapter id="structs">
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<title>Structures</title>
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<para>
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This chapter contains the autogenerated documentation of the structures which are
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used in the Reed-Solomon Library and are relevant for a developer.
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</para>
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!Iinclude/linux/rslib.h
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</chapter>
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<chapter id="pubfunctions">
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<title>Public Functions Provided</title>
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<para>
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This chapter contains the autogenerated documentation of the Reed-Solomon functions
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which are exported.
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</para>
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!Elib/reed_solomon/reed_solomon.c
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</chapter>
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<chapter id="credits">
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<title>Credits</title>
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<para>
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The library code for encoding and decoding was written by Phil Karn.
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</para>
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<programlisting>
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Copyright 2002, Phil Karn, KA9Q
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May be used under the terms of the GNU General Public License (GPL)
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</programlisting>
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<para>
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The wrapper functions and interfaces are written by Thomas Gleixner.
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</para>
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<para>
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Many users have provided bugfixes, improvements and helping hands for testing.
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Thanks a lot.
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</para>
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<para>
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The following people have contributed to this document:
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</para>
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<para>
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Thomas Gleixner<email>tglx@linutronix.de</email>
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</para>
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</chapter>
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</book>
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@ -19,6 +19,7 @@ Core utilities
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workqueue
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genericirq
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flexible-arrays
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librs
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Interfaces for kernel debugging
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===============================
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212
Documentation/core-api/librs.rst
Normal file
212
Documentation/core-api/librs.rst
Normal file
@ -0,0 +1,212 @@
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==========================================
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Reed-Solomon Library Programming Interface
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==========================================
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:Author: Thomas Gleixner
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Introduction
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============
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The generic Reed-Solomon Library provides encoding, decoding and error
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correction functions.
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Reed-Solomon codes are used in communication and storage applications to
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ensure data integrity.
|
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|
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This documentation is provided for developers who want to utilize the
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functions provided by the library.
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Known Bugs And Assumptions
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==========================
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None.
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Usage
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=====
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This chapter provides examples of how to use the library.
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Initializing
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------------
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The init function init_rs returns a pointer to an rs decoder structure,
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which holds the necessary information for encoding, decoding and error
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correction with the given polynomial. It either uses an existing
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matching decoder or creates a new one. On creation all the lookup tables
|
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for fast en/decoding are created. The function may take a while, so make
|
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sure not to call it in critical code paths.
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::
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/* the Reed Solomon control structure */
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static struct rs_control *rs_decoder;
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/* Symbolsize is 10 (bits)
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* Primitive polynomial is x^10+x^3+1
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* first consecutive root is 0
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* primitive element to generate roots = 1
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* generator polynomial degree (number of roots) = 6
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*/
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rs_decoder = init_rs (10, 0x409, 0, 1, 6);
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Encoding
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--------
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The encoder calculates the Reed-Solomon code over the given data length
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and stores the result in the parity buffer. Note that the parity buffer
|
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must be initialized before calling the encoder.
|
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|
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The expanded data can be inverted on the fly by providing a non-zero
|
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inversion mask. The expanded data is XOR'ed with the mask. This is used
|
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e.g. for FLASH ECC, where the all 0xFF is inverted to an all 0x00. The
|
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Reed-Solomon code for all 0x00 is all 0x00. The code is inverted before
|
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storing to FLASH so it is 0xFF too. This prevents that reading from an
|
||||
erased FLASH results in ECC errors.
|
||||
|
||||
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
|
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the moment. If it is necessary it should be not a big deal to implement
|
||||
such functionality.
|
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|
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::
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/* Parity buffer. Size = number of roots */
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uint16_t par[6];
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/* Initialize the parity buffer */
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memset(par, 0, sizeof(par));
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/* Encode 512 byte in data8. Store parity in buffer par */
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encode_rs8 (rs_decoder, data8, 512, par, 0);
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Decoding
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--------
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The decoder calculates the syndrome over the given data length and the
|
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received parity symbols and corrects errors in the data.
|
||||
|
||||
If a syndrome is available from a hardware decoder then the syndrome
|
||||
calculation is skipped.
|
||||
|
||||
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.
|
||||
|
||||
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.
|
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|
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Decoding with syndrome calculation, direct data correction
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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::
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/* Parity buffer. Size = number of roots */
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uint16_t par[6];
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uint8_t data[512];
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int numerr;
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/* Receive data */
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||||
.....
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/* Receive parity */
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||||
.....
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||||
/* Decode 512 byte in data8.*/
|
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numerr = decode_rs8 (rs_decoder, data8, par, 512, NULL, 0, NULL, 0, NULL);
|
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Decoding with syndrome given by hardware decoder, direct data correction
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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::
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/* Parity buffer. Size = number of roots */
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uint16_t par[6], syn[6];
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uint8_t data[512];
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int numerr;
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/* Receive data */
|
||||
.....
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/* Receive parity */
|
||||
.....
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/* Get syndrome from hardware decoder */
|
||||
.....
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||||
/* Decode 512 byte in data8.*/
|
||||
numerr = decode_rs8 (rs_decoder, data8, par, 512, syn, 0, NULL, 0, NULL);
|
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|
||||
|
||||
Decoding with syndrome given by hardware decoder, no direct data correction.
|
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Note: It's not necessary to give data and received parity to the
|
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decoder.
|
||||
|
||||
::
|
||||
|
||||
/* 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]);
|
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}
|
||||
|
||||
|
||||
Cleanup
|
||||
-------
|
||||
|
||||
The function free_rs frees the allocated resources, if the caller is
|
||||
the last user of the decoder.
|
||||
|
||||
::
|
||||
|
||||
/* Release resources */
|
||||
free_rs(rs_decoder);
|
||||
|
||||
|
||||
Structures
|
||||
==========
|
||||
|
||||
This chapter contains the autogenerated documentation of the structures
|
||||
which are used in the Reed-Solomon Library and are relevant for a
|
||||
developer.
|
||||
|
||||
.. kernel-doc:: include/linux/rslib.h
|
||||
:internal:
|
||||
|
||||
Public Functions Provided
|
||||
=========================
|
||||
|
||||
This chapter contains the autogenerated documentation of the
|
||||
Reed-Solomon functions which are exported.
|
||||
|
||||
.. kernel-doc:: lib/reed_solomon/reed_solomon.c
|
||||
:export:
|
||||
|
||||
Credits
|
||||
=======
|
||||
|
||||
The library code for encoding and decoding was written by Phil Karn.
|
||||
|
||||
::
|
||||
|
||||
Copyright 2002, Phil Karn, KA9Q
|
||||
May be used under the terms of the GNU General Public License (GPL)
|
||||
|
||||
|
||||
The wrapper functions and interfaces are written by Thomas Gleixner.
|
||||
|
||||
Many users have provided bugfixes, improvements and helping hands for
|
||||
testing. Thanks a lot.
|
||||
|
||||
The following people have contributed to this document:
|
||||
|
||||
Thomas Gleixner\ tglx@linutronix.de
|
||||
Loading…
Reference in New Issue
Block a user