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>

2 files changed, 213 insertions, 0 deletions

diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index 62abd36bfffb..0606be3a3111 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -19,6 +19,7 @@ Core utilities
    workqueue
    genericirq
    flexible-arrays
+   librs
 
 Interfaces for kernel debugging
 ===============================
diff --git a/Documentation/core-api/librs.rst b/Documentation/core-api/librs.rst
new file mode 100644
index 000000000000..6010f5bc5bf9
--- /dev/null
+++ b/Documentation/core-api/librs.rst
@@ -0,0 +1,212 @@
+==========================================
+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