高通平臺 GPIO interface Guide
A GPIO pin can be configured as a general input, output, or one of several alternate functions. When used as input, a GPIO pin can also be set up as an interrupt source, and a subset of GPIOs are capable of generating interrupts that can bring an MSMTM out of deep sleep (XO shutdown or VDD minimization). Also, GPIO can be configured to have internal pull (up, down, or no-pull) circuits and different driving strength.
The GPIO, or the Top-Level Module Multiplex (TLMM) driver is built on top of the Hardware Abstraction Layer (HAL) framework.
In the new software architecture, HAL provides a layer that insulates the drivers from the details of the underlying hardware design. Moreover, a Device Abstraction Layer (DAL) is also placed between the driver code and application code to provide similar insulation between the device drivers and application software.
可參考的博文總結：
http://blog.csdn.net/s_jason/article/details/73864103
配置學習總結高通平臺GPIO http://blog.csdn.net/Joymine/article/details/48161895
http://blog.csdn.net/eliot_shao/article/details/53836216高通GPIO配置簡介 http://blog.csdn.net/ldinvicible/article/details/52421640
高通平臺GPIO控制例子-http://www.elecfans.com/emb/dsp/20170223488002.html