EnableDisplayHeader

Synopsis

Header: fxcg/display.h
Syscall index: 0x1D7F
Function signature: void EnableDisplayHeader(int action, int value)

The function of this syscall is still unknown.

Parameters

• action If action == 0 clear 0xFD80178C. If action == 2 set 0xFD80178C to value. If action is any other value return 0xFD80178C unmodified.
• value Used only if action == 2
  

Returns

The final value of 0xFD80178C which may be modified depending on the value of action.

Comments

Similar functions have been proven to use different addresses depending on the OS version. Versions of this code from other OS versions have not been documented. Unless it is proven that all OS versions use the same address use this function instead of relying on 0xFD80178C being the same for all OS versions.

! If r4==0 clear 0xFD80178C
! If r4==2 set 0xFD80178C to r5
! Other	values of r4 will cause	the function to	simply return the contents of 0xFD80178C

EnableDisplayHeader:
		tst	r4, r4
		bf	r4NonZero	! Branch if r4 is non-zero
		mov.l	#unk_FD80178C, r4 ! If r4 is zero set r4 to 0xFD80178C
		mov	#0, r2
		bra	EnableDisplayHeader_exit
		mov.l	r2, @r4		! Before branching clear the contents of 0xFD80178C
! ---------------------------------------------------------------------------

r4NonZero:
		mov	r4, r0
		cmp/eq	#2, r0
		bf	EnableDisplayHeader_exit ! Branch if r4!=2 without delay
		mov.l	#unk_FD80178C, r4
		mov.l	r5, @r4

EnableDisplayHeader_exit:
		mov.l	#unk_FD80178C, r4
		rts
		mov.l	@r4, r0		! Return the contents of 0xFD80178C
! End of function EnableDisplayHeader