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Documentation/i2c: sync docs with current state of i2c-tools 

Currently, Documentation/i2c/dev-interface describes the use of
i2c_smbus_* helper routines as static inlined functions provided by
linux/i2c-dev.h.  Work has been done to refactor the linux/i2c-dev.h file
in the i2c-tools project out into its own library.  As a result, these
docs have become stale.

This patch corrects the discrepancy and directs the reader to the
i2c-tools project for more information.

Signed-off-by: Sam Hansen <hansens@google.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Sam Hansen 2018-04-13 10:42:56 -07:00 committed by Wolfram Sang
parent 675edea10b
commit b50cb3eaf7
1 changed files with 5 additions and 11 deletions
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Documentation/i2c/dev-interface
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@ -23,11 +23,6 @@ First, you need to include these two headers:
#include <linux/i2c-dev.h>
#include <i2c/smbus.h>
(Please note that there are two files named "i2c-dev.h" out there. One is
distributed with the Linux kernel and the other one is included in the
source tree of i2c-tools. They used to be different in content but since 2012
they're identical. You should use "linux/i2c-dev.h").
Now, you have to decide which adapter you want to access. You should
inspect /sys/class/i2c-dev/ or run "i2cdetect -l" to decide this.
Adapter numbers are assigned somewhat dynamically, so you can not
@ -140,8 +135,8 @@ ioctl(file, I2C_RDWR, struct i2c_rdwr_ioctl_data *msgset)
set in each message, overriding the values set with the above ioctl's.
ioctl(file, I2C_SMBUS, struct i2c_smbus_ioctl_data *args)
Not meant to be called directly; instead, use the access functions
below.
If possible, use the provided i2c_smbus_* methods described below instead
of issuing direct ioctls.
You can do plain i2c transactions by using read(2) and write(2) calls.
You do not need to pass the address byte; instead, set it through
@ -166,10 +161,9 @@ what happened. The 'write' transactions return 0 on success; the
returns the number of values read. The block buffers need not be longer
than 32 bytes.
The above functions are all inline functions, that resolve to calls to
the i2c_smbus_access function, that on its turn calls a specific ioctl
with the data in a specific format. Read the source code if you
want to know what happens behind the screens.
The above functions are made available by linking against the libi2c library,
which is provided by the i2c-tools project. See:
https://git.kernel.org/pub/scm/utils/i2c-tools/i2c-tools.git/.
Implementation details