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authorCengiz C <cengizc@gmail.com>2017-12-12 19:43:09 +0300
committerJonathan Corbet <corbet@lwn.net>2017-12-21 13:39:30 -0700
commit91b28aeb17ce13065d745a1f92c95011c10ba75a (patch)
tree426ec7d073a1ff2ed0b75ca5b3ae77af8550874f
parent90b2a01e68167665a3f86c477414e795cd4a0139 (diff)
i2c: update i2c-dev.h warning in documentation
`Documentation/i2c/dev-interface` gives examples for accessing i2c from userspace. There's a note that warns developers about the two `i2c-dev.h` header files which were shipped with the kernel and i2c-tools separately. However, following i2c-tools commits suggest that the header files are now identical (in functionality) and `i2c_*` helper functions are now defined in a separate header called `i2c/smbus.h`, which is distributed with i2c-tools: commit 652619121974 ("Minimize differences with kernel flavor") commit 93caf007f4cb ("Move SMBus helper functions to include/i2c/smbus.h") Thus, I've converted the warning paragraph into a historical note and updated the suggested header files. Signed-off-by: Cengiz Can <cengizc@gmail.com> Cc: Wolfram Sang <wsa@the-dreams.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
-rw-r--r--Documentation/i2c/dev-interface17
1 files changed, 10 insertions, 7 deletions
diff --git a/Documentation/i2c/dev-interface b/Documentation/i2c/dev-interface
index 5ff19447ac44..d04e6e4964ee 100644
--- a/Documentation/i2c/dev-interface
+++ b/Documentation/i2c/dev-interface
@@ -17,13 +17,16 @@ i2c-10, ...). All 256 minor device numbers are reserved for i2c.
C example
=========
-So let's say you want to access an i2c adapter from a C program. The
-first thing to do is "#include <linux/i2c-dev.h>". Please note that
-there are two files named "i2c-dev.h" out there, one is distributed
-with the Linux kernel and is meant to be included from kernel
-driver code, the other one is distributed with i2c-tools and is
-meant to be included from user-space programs. You obviously want
-the second one here.
+So let's say you want to access an i2c adapter from a C program.
+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.