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>
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@ -17,13 +17,16 @@ i2c-10, ...). All 256 minor device numbers are reserved for i2c.
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C example
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=========
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So let's say you want to access an i2c adapter from a C program. The
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first thing to do is "#include <linux/i2c-dev.h>". Please note that
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there are two files named "i2c-dev.h" out there, one is distributed
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with the Linux kernel and is meant to be included from kernel
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driver code, the other one is distributed with i2c-tools and is
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meant to be included from user-space programs. You obviously want
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the second one here.
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So let's say you want to access an i2c adapter from a C program.
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First, you need to include these two headers:
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#include <linux/i2c-dev.h>
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#include <i2c/smbus.h>
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(Please note that there are two files named "i2c-dev.h" out there. One is
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distributed with the Linux kernel and the other one is included in the
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source tree of i2c-tools. They used to be different in content but since 2012
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they're identical. You should use "linux/i2c-dev.h").
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Now, you have to decide which adapter you want to access. You should
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inspect /sys/class/i2c-dev/ or run "i2cdetect -l" to decide this.
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