Usually the GPIOs for sensors are directly implemented in the drivers and exposed to the Android HAL for that particular device, same for the hardware buttons on phones/tablets. Android Linux runtime usually does not use /sys or /dev devices with some rare exceptions... it's not a general purpose OS. That's not to say you can't write a driver that exposes GPIOs through the HAL as an Android service, maybe there is already somehting like that around somewhere...
Look at : http://de.slideshare.net/linaroorg/sfo15...or-android for an example how I2C and GPIO can be implemented
Look at : http://de.slideshare.net/linaroorg/sfo15...or-android for an example how I2C and GPIO can be implemented
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