Merge tag 'docs-4.13' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "There has been a fair amount of activity in the docs tree this time
  around. Highlights include:

   - Conversion of a bunch of security documentation into RST

   - The conversion of the remaining DocBook templates by The Amazing
     Mauro Machine. We can now drop the entire DocBook build chain.

   - The usual collection of fixes and minor updates"

* tag 'docs-4.13' of git://git.lwn.net/linux: (90 commits)
  scripts/kernel-doc: handle DECLARE_HASHTABLE
  Documentation: atomic_ops.txt is core-api/atomic_ops.rst
  Docs: clean up some DocBook loose ends
  Make the main documentation title less Geocities
  Docs: Use kernel-figure in vidioc-g-selection.rst
  Docs: fix table problems in ras.rst
  Docs: Fix breakage with Sphinx 1.5 and upper
  Docs: Include the Latex "ifthen" package
  doc/kokr/howto: Only send regression fixes after -rc1
  docs-rst: fix broken links to dynamic-debug-howto in kernel-parameters
  doc: Document suitability of IBM Verse for kernel development
  Doc: fix a markup error in coding-style.rst
  docs: driver-api: i2c: remove some outdated information
  Documentation: DMA API: fix a typo in a function name
  Docs: Insert missing space to separate link from text
  doc/ko_KR/memory-barriers: Update control-dependencies example
  Documentation, kbuild: fix typo "minimun" -> "minimum"
  docs: Fix some formatting issues in request-key.rst
  doc: ReSTify keys-trusted-encrypted.txt
  doc: ReSTify keys-request-key.txt
  ...

3 files changed, 217 insertions, 1 deletions

diff --git a/Documentation/core-api/assoc_array.rst b/Documentation/core-api/assoc_array.rst
index d83cfff9ea43..8231b915c939 100644
--- a/Documentation/core-api/assoc_array.rst
+++ b/Documentation/core-api/assoc_array.rst
@@ -10,7 +10,10 @@ properties:
 
 1. Objects are opaque pointers.  The implementation does not care where they
    point (if anywhere) or what they point to (if anything).
-.. note:: Pointers to objects _must_ be zero in the least significant bit.
+
+   .. note::
+
+      Pointers to objects _must_ be zero in the least significant bit.
 
 2. Objects do not need to contain linkage blocks for use by the array.  This
    permits an object to be located in multiple arrays simultaneously.
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