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Commit 8aba7848 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

docs-rst: convert librs book to ReST 



Use pandoc to convert documentation to ReST by calling
Documentation/sphinx/tmplcvt script.

Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent e85ca0a3

Documentation/DocBook/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ 


DOCBOOKS := \

	    lsm.xml \

	    mtdnand.xml librs.xml \

	    mtdnand.xml \

	    sh.xml



ifeq ($(DOCBOOKS),)

Documentation/DocBook/librs.tmpl

deleted100644 → 0
+0 −289
Original line number Diff line number Diff line 
<?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 &lt; 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>

Documentation/core-api/index.rst

+1 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ Core utilities 
   workqueue

   genericirq

   flexible-arrays

   librs



Interfaces for kernel debugging

===============================

Documentation/core-api/librs.rst

0 → 100644
+212 −0
Original line number Diff line number Diff line 
==========================================

Reed-Solomon Library Programming Interface

==========================================



:Author: Thomas Gleixner



Introduction

============



The generic Reed-Solomon Library provides encoding, decoding and error

correction functions.



Reed-Solomon codes are used in communication and storage applications to

ensure data integrity.



This documentation is provided for developers who want to utilize the

functions provided by the library.



Known Bugs And Assumptions

==========================



None.



Usage

=====



This chapter provides examples of how to use the library.



Initializing

------------



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.



::



    /* 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);





Encoding

--------



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.



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.



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.



::



    /* 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);





Decoding

--------



The decoder calculates the syndrome over the given data length and the

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.



Decoding with syndrome calculation, direct data correction

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



::



    /* 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);





Decoding with syndrome given by hardware decoder, direct data correction

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



::



    /* 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);





Decoding with syndrome given by hardware decoder, no direct data correction.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



Note: It's not necessary to give data and received parity to the

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]);

    }





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