Hello all,
Here is how i was able to access , read , write to sysfs from an android
application .
Ramdisk / device specific changes
#init.{hardware}.rc
>
> on property:sys.boot_completed=1
>
> #UART5 on my device
> chown root root /dev/ttymxc4
> chmod 0777 /dev/ttymxc4
> #GPIO5_IO14 (gpio_bank - 1) * 32 + gpio_bitwrite /sys/class/gpio/export
> 142
> write /sys/class/gpio/gpio142/edge "both"
>
> #ueventd.{hardware}.rc
> +/dev/ttymxc* 0666 system system
>
Then using JNI i was able to access uart and gpio pin .
Here are both application source code
UART: https://github.com/sooorajjj/BluemoonUART
<https://www.google.com/url?q=https://github.com/sooorajjj/BluemoonUART&sa=D&source=hangouts&ust=1527226851456000&usg=AFQjCNGparXoQ2yPbiFH74V9DUo9uXzIVA>
GPIO: https://github.com/sooorajjj/BluemoonGPIO
Note these application were not created by me , its available as example on
google i just had to make a few changes for it to work on my device .
GPIO led blink example and reading input from button is what i have tested
and works.
UART reading and writing using serial console works .
On Monday, April 3, 2017 at 9:30:05 PM UTC+5:30, himanshu wrote:
>
> Android application in java having permission issues when accessing sysfs
> entry.
>
> try{
> FileOutputStream fos = new
> FileOutputStream("/sys/class/shift_reg/shift_reg/value");
> byte mybyte = 1;
> fos.write(mybyte);
> fos.close();} catch ( Exception e) {
> Log.d(TAG, "Failed in writing to Shift Register"); <------- I am always
> getting this exception.}
>
>
> 1) Have tried putting 'setenforce 0'. Does't work. Even though enforce
> level is permissive.
>
> 2) Do I have to access using JNI way: ( android-app -> jni -> driver )
>
> 3) I have set file permission as 0777 for the sysfs node file.
>
>
> Dmesg Error message:
>
> [ 417.176302] type=1400 audit(418.589:63): avc: denied { write } for
> pid=3164 comm="com.android.cam" name="value" dev="sysfs" ino=9749
> scontext=u:r:untrusted_app:s0 tcontext=u:object_r:sysfs:s0 tclass=file
> permissive=1
>
> ps -Z
>
> u:r:untrusted_app:s0 u0_a67 4360 333
> com.android.cam
>
>
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