Re: [lm-sensors] Application using i2c-imx.c

[Jean Delvare <khali@linux-fr.org>]

Hi Javier,

What about NOT TOP-POSTING, as I requested once already?

On Wed, 9 Dec 2009 16:29:34 +0100, Javier Zugasti wrote:
> Thank you very much for your reply Jean.
> I patched the kernel tree with the patch you linked me to and then selected
> the hwmon and lm73 option in the menuconfig options (together with the i2c
> of course).
> 
> After that I used a cross-compiler to compile the kernel for my board and
> transferred the images to my board and started my linux there.
> 
> I assume the system supports i2c now.
> No i2c devices appear in the /dev directory or in /sys/bus/i2c/devices

Which kernel are you running? I2C adapters only show
in /sys/bus/i2c/devices since kernel 2.6.32. For older kernels you
would look for them in /sys/class/i2c-adapter.

Assuming you run an older kernel, please list the entries
under /sys/class/i2c-adapter.

, but
> the lm73 appears in /sys/bus/i2c/drivers and i2c appears in the file
> /proc/devices:
> 
> cat /proc/devices
> Character devices:
> ...
> *89 i2c*
> ...

This means i2c-dev is loaded, but you shouldn't need it, see below.

> So now, how can I write an application in the user space that reads the
> temperature from the lm73? Do I have to use IOCTL calls or how do I do it?

With the lm73 driver you're using, access to the LM73 chip is done
through sysfs, very easily. You would have to go through ioctls
on /dev/i2c* nodes only if you did _not_ have a kernel driver for the
LM73.

-- 
Jean Delvare
http://khali.linux-fr.org/wishlist.html

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