关于库函数中结构体指针问题

关于库文件中typedef 结构体指针定义出现了好几种不同的定义方法：

以Hal结构体定义为例：

typedef struct _HAL_Obj_
{
  ADC_Handle    adcHandle;        //!< the ADC handle

  CLK_Handle    clkHandle;        //!< the clock handle
 
  CPU_Handle    cpuHandle;        //!< the CPU handle

  DRV8305_Handle drv8305Handle;   //!< the drv8305 interface handle
  DRV8305_Obj    drv8305;         //!< the drv8305 interface object

} HAL_Obj;


//! \brief      Defines the HAL handle
//! \details    The HAL handle is a pointer to a HAL object.  In all HAL functions
//!             the HAL handle is passed so that the function knows what peripherals
//!             are to be accessed.
//!
typedef struct _HAL_Obj_ *HAL_Handle;

在HAL初始化函数中：

HAL_Handle HAL_init(void *pMemory,const size_t numBytes)
{
uint_least8_t cnt;
HAL_Handle handle;
HAL_Obj *obj;

if(numBytes < sizeof(HAL_Obj))
return((HAL_Handle)NULL);

// assign the handle
handle = (HAL_Handle)pMemory;

// assign the object
obj = (HAL_Obj *)handle;

// initialize the watchdog driver
obj->wdogHandle = WDOG_init((void *)WDOG_BASE_ADDR,sizeof(WDOG_Obj));

// disable watchdog
HAL_disableWdog(handle);

// initialize the ADC
obj->adcHandle = ADC_init((void *)ADC_BASE_ADDR,sizeof(ADC_Obj));

return(handle);
}

handle和obj难道不都是两个结构体指针吗？为什么要定义两个？而且同样是两个，为什么还要采用两种不同的形式？

还有关于GPIO的结构体指针中还出现了其他版本：

第一个版本是FOC的28027的foc的lab例程中的

typedef struct _GPIO_Obj_
{
  volatile uint32_t GPACTRL;         //!< GPIO A Control Register
  volatile uint32_t GPAQSEL1;        //!< GPIO A Qualifier Select 1 Register
  volatile uint32_t GPAQSEL2;        //!< GPIO A Qualifier Select 2 Register
} GPIO_Obj;

//! \brief Defines the general purpose I/O (GPIO) handle
//!
typedef struct _GPIO_Obj_ *GPIO_Handle;

下面一个是F28027的controlSUITE的V2.30库函数中的：

typedef struct _GPIO_Obj_
{
    volatile uint32_t GPACTRL;         //!< GPIO A Control Register
    volatile uint32_t GPAQSEL1;        //!< GPIO A Qualifier Select 1 Register
    volatile uint32_t GPAQSEL2;        //!< GPIO A Qualifier Select 2 Register
} GPIO_Obj;

//! \brief Defines the general purpose I/O (GPIO) handle
//!
typedef struct GPIO_Obj   *GPIO_Handle;

这两种定义方式又有什么区别呢？了

typedef struct GPIO_Obj *GPIO_Handle;这么定义是不是应该去掉一个struct，因为GPIO_Obj就相当于struct _GPIO_Obj_ 了。