I got this working!
Basically I did not realize that SYSFS was more sophisticated than /
proc and actually supported file permissions.
This is basically what I did to access a GPIO from Java land.
echo "128" >/sys/class/gpio/export
echo "out" > /sys/devices/virtual/gpio/gpio128/direction
chmod 0666 /sys/devices/virtual/gpio/gpio128/value
Now you have GPIO #128 exported in sysfs, configured as an output and
accessible to your Java application.
Anything else that is accessible via sysfs can be handled in a similar
way.
Enjoy!
On Dec 29, 4:36 pm, A Curtis <ajcurti...@gmail.com> wrote:
> Chris,
>
> Have you tried to access sysfs directly frdom Java? I have not been
> able to get this to work.
>
> Could you provide a code fragment?
>
> TIA
>
> On Nov 23, 10:12 am, Chris Stratton <cs07...@gmail.com> wrote:
>
>
>
>
>
>
>
> > On Nov 23, 5:33 am, Mikkel Christensen <mikkel.christen...@ixonos.com>
> > wrote:
>
> > > If the LED is already exposed in sysfs you are lucky and it should be
> > > quite easy. Otherwise create a Kernel device driver that does the
> > > exposure of the LED to sysfs.
>
> > If it's already exposed in sysfs, you don't need to use native code.
> > You should be able to access the special file directly from java if
> > you have the permissions set right. If they are wrong, you can't
> > access it from the ndk either.
>
> > > Then in the /jni/native.cpp function do the proper write to the sysfs
> > > entry like this (note: this depends on how the led is exposed trough
> > > sysfs):
>
> > > ret = system("echo 1 > /sys/class/leds/red/brightness");
>
> > Chaining the echo command seems wasteful. Why not just write to the
> > special file yourself?
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