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i2c: slave: docs: be more precise about the prerequsites 

There was some confusion what was needed to utilize the slave support,
so let's be more precise about this. Add an introductory paragraph to
the development section while we are here.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Wolfram Sang 2015-05-14 14:40:04 +02:00 committed by Wolfram Sang
parent 1fb2ad9565
commit 976cf2056c
1 changed files with 15 additions and 10 deletions
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25
Documentation/i2c/slave-interface
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@ -3,16 +3,16 @@ Linux I2C slave interface description
by Wolfram Sang <wsa@sang-engineering.com> in 2014-15
Linux can also be an I2C slave in case I2C controllers have slave support.
Besides this HW requirement, one also needs a software backend providing the
actual functionality. An example for this is the slave-eeprom driver, which
acts as a dual memory driver. While another I2C master on the bus can access it
like a regular EEPROM, the Linux I2C slave can access the content via sysfs and
retrieve/provide information as needed. The software backend driver and the I2C
bus driver communicate via events. Here is a small graph visualizing the data
flow and the means by which data is transported. The dotted line marks only one
example. The backend could also use e.g. a character device, be in-kernel
only, or something completely different:
Linux can also be an I2C slave if the I2C controller in use has slave
functionality. For that to work, one needs slave support in the bus driver plus
a hardware independent software backend providing the actual functionality. An
example for the latter is the slave-eeprom driver, which acts as a dual memory
driver. While another I2C master on the bus can access it like a regular
EEPROM, the Linux I2C slave can access the content via sysfs and handle data as
needed. The backend driver and the I2C bus driver communicate via events. Here
is a small graph visualizing the data flow and the means by which data is
transported. The dotted line marks only one example. The backend could also
use a character device, be in-kernel only, or something completely different:
e.g. sysfs I2C slave events I/O registers
@ -43,6 +43,11 @@ behaviour and setup.
Developer manual
================
First, the events which are used by the bus driver and the backend will be
described in detail. After that, some implementation hints for extending bus
drivers and writing backends will be given.
I2C slave events
----------------