AD5274 userspace driver

Question

We are using the ad5274 device to control an LCD contrast pin. I have successfully instantiated the ad5274 linux driver. The driver exposes a couple of files in /sys/bus/i2c/devices/000-02c. The files of note are rdac0, otp0en, and otp0. I can't find any documentation that explains how someone is to use these files to program the ad5274 device. Any help?

mhennerich · Accepted Answer

Hi Michael, 
 Sorry for the delay - we tested the AD5272/5274 support using a AD5272 which always worked flawless. 
 In fact there is typo which caused the AD5274 read-back problems. 
 A fix was send mainline: 
 LKML: <michael.hennerich@analog ...: [PATCH] drivers/misc/ad525x_dpot: AD5274 fix RDAC read back errors 
 Testing: 
 root@linaro-ubuntu-desktop:~# cd /sys/bus/i2c/devices/0-002f/ 
 root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# ls -al 
 total 0 
 drwxr-xr-x 3 root root 0 Jan 1 1970 . 
 drwxr-xr-x 6 root root 0 Jan 1 1970 .. 
 lrwxrwxrwx 1 root root 0 Feb 22 09:36 driver -> ../../../../../../bus/i2c/drivers/ad_dpot 
 -r--r--r-- 1 root root 4096 Feb 22 09:36 modalias 
 -r--r--r-- 1 root root 4096 Feb 22 09:36 name 
 lrwxrwxrwx 1 root root 0 Feb 22 09:36 of_node -> ../../../../../../firmware/devicetree/base/amba/i2c@e0004000/ad5172@2f 
 -rw-r--r-- 1 root root 4096 Feb 22 09:36 otp0 
 -rw-r--r-- 1 root root 4096 Feb 22 09:36 otp0en 
 drwxr-xr-x 2 root root 0 Feb 22 09:36 power 
 -rw-r--r-- 1 root root 4096 Feb 22 09:36 rdac0 
 lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem -> ../../../../../../bus/i2c 
 -rw-r--r-- 1 root root 4096 Jan 1 1970 uevent 
 root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# grep "" * 
 modalias:i2c:ad5274 
 name:ad5274 
 otp0:42 
 otp0en:disabled 
 rdac0:42 
 uevent:DRIVER=ad_dpot 
 uevent:OF_NAME=ad5172 
 uevent:OF_FULLNAME=/amba/i2c@e0004000/ad5172@2f 
 uevent:OF_COMPATIBLE_0=ad5274 
 uevent:OF_COMPATIBLE_N=1 
 uevent:MODALIAS=i2c:ad5274 
 root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# for i in `seq 0 255`; do echo $i > rdac0;cat rdac0; done; 
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 [ --snip-- ] 
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 255 
 root@linaro-ubuntu-desktop:/sys/bus/i2c/devices/0-002f# 
 -Michael)

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AD5274 userspace driver