i2c: Add kernel documentation

Generate I2C kerneldoc; fix various glitches and add "context" sections to
that documentation.  Most I2C and SMBus functions still have no kerneldoc.

Let me suggest providing kerneldoc for all the i2c_smbus_*() functions as
a small and mostly self-contained project for anyone so inclined.  :)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 55 insertions, 0 deletions

diff --git a/Documentation/DocBook/kernel-api.tmpl b/Documentation/DocBook/kernel-api.tmpl
index 8c5698a8c2e1..46bcff2849bd 100644
--- a/Documentation/DocBook/kernel-api.tmpl
+++ b/Documentation/DocBook/kernel-api.tmpl
@@ -643,6 +643,60 @@ X!Idrivers/video/console/fonts.c
 !Edrivers/spi/spi.c
   </chapter>
 
+  <chapter id="i2c">
+     <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
+
+     <para>
+        I<superscript>2</superscript>C (or without fancy typography, "I2C")
+        is an acronym for the "Inter-IC" bus, a simple bus protocol which is
+        widely used where low data rate communications suffice.
+        Since it's also a licensed trademark, some vendors use another
+        name (such as "Two-Wire Interface", TWI) for the same bus.
+        I2C only needs two signals (SCL for clock, SDA for data), conserving
+        board real estate and minimizing signal quality issues.
+        Most I2C devices use seven bit addresses, and bus speeds of up
+        to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
+        found wide use.
+        I2C is a multi-master bus; open drain signaling is used to
+        arbitrate between masters, as well as to handshake and to
+        synchronize clocks from slower clients.
+     </para>
+
+     <para>
+        The Linux I2C programming interfaces support only the master
+        side of bus interactions, not the slave side.
+        The programming interface is structured around two kinds of driver,
+        and two kinds of device.
+        An I2C "Adapter Driver" abstracts the controller hardware; it binds
+        to a physical device (perhaps a PCI device or platform_device) and
+        exposes a <structname>struct i2c_adapter</structname> representing
+        each I2C bus segment it manages.
+        On each I2C bus segment will be I2C devices represented by a
+        <structname>struct i2c_client</structname>.  Those devices will
+        be bound to a <structname>struct i2c_driver</structname>,
+        which should follow the standard Linux driver model.
+        (At this writing, a legacy model is more widely used.)
+        There are functions to perform various I2C protocol operations; at
+        this writing all such functions are usable only from task context.
+     </para>
+
+     <para>
+        The System Management Bus (SMBus) is a sibling protocol.  Most SMBus
+        systems are also I2C conformant.  The electrical constraints are
+        tighter for SMBus, and it standardizes particular protocol messages
+        and idioms.  Controllers that support I2C can also support most
+        SMBus operations, but SMBus controllers don't support all the protocol
+        options that an I2C controller will.
+        There are functions to perform various SMBus protocol operations,
+        either using I2C primitives or by issuing SMBus commands to
+        i2c_adapter devices which don't support those I2C operations.
+     </para>
+
+!Iinclude/linux/i2c.h
+!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
+!Edrivers/i2c/i2c-core.c
+  </chapter>
+
   <chapter id="splice">
       <title>splice API</title>
   <para>)
@@ -654,4 +708,5 @@ X!Idrivers/video/console/fonts.c
 !Ffs/splice.c
   </chapter>
 
+
 </book>