Outport and Inport with Microsoft Visual C++

[Jeko]

I always develop with gcc, but now I'm developing with visual C++ from Microsoft.
With gcc I use this functions for outport and inport:

Code: Select all

inline unsigned char inportb(unsigned short int port)
{
        unsigned char ret;
        asm volatile ("inb %%dx,%%al":"=a" (ret):"d"(port));
        return ret;
}

inline void outportb(unsigned short int port, unsigned char value)
{
        asm volatile ("outb %%al,%%dx": :"d" (port), "a"(value));
}

How can I make this with Visual C++?[/code]

[delroth]

With Visual C++, you can use Intel syntax for inline assembler.
So your code is :

Code: Select all

inline unsigned char inportb(unsigned short int port) 
{ 
        unsigned char ret; 
        __asm
        {
                in port, ret
        }
        return ret; 
} 
 
inline void outportb(unsigned short int port, unsigned char value) 
{ 
        __asm
        {
                out port, value
        }
}

[Thomac]

With Intel syntax you are still restricted to using registers with IN and OUT.
OUT and IN only accept DX as the address, and any 8 bit register as input/output. (AL, BL, BH, AH, etcetera)

This snippet shouldn't throw opcode/syntax errors:

Code: Select all

inline unsigned char inportb(unsigned short int port)
{
        _asm
        {
                mov dx, word ptr [port]
                in dx, al
                stos byte ptr [port]
        }
        return port;
}
 
inline void outportb(unsigned short int port, unsigned char value)
{
        _asm
        {
                mov dx, word ptr [port]
                lods byte ptr [value]
                out dx, al
        }
}

[Jeko]

thank you very much!

[Jeko]

There are some errors in your code!
They don't work!

[Thomac]

For some reason I can't get the IN instruction to work.
I managed to get outportb to work though:

Code: Select all

_inline void outportb(unsigned short int port, unsigned char value)
{
        _asm
        {
                mov dx, word ptr [port]
                mov al, byte ptr [value]
                out dx, al
        }
}

[Jeko]

thank you, outportb works!
But, what can I make with inportb?

[Thomac]

I forgot that dx and al's positions are reversed with IN.
Here's a working version:

Code: Select all

_inline char outportb(unsigned short int port)
{
        _asm
        {
                mov dx, word ptr [port]
                in al, dx
                mov al, byte ptr [port]
        }
        return (char)port;
}

[Jeko]

thank you! Now it works