Can i write data to bar reg ?

[hushunkui]

Hi, sir:
when i get bar address, can i write or read data to bar reg? ex: bar+0, bar+1..........

[karcherm]

You can't access the device itself using pci. That tool is only meant to configure PCI devices, not to access PCI devices. The incomplete and not yet documented tool hw on the other hand can already access I/O ports described by the BAR of a PCI device. If BAR1 of function 3 of device 7 on bus 0 is an I/O range, this invocation of hw is supposed to work:

hw inb 00:07.3$1+7

This will read the port at offset 7 inside the I/O region described by BAR1 (counting starts at BAR0). As hw is still unfinished, it's not yet included in a release, but you would need to compile it yourself.

Memory access in hw is not yet implemented, and implementing access to arbitrary memory space from a 16-bit DOS executable is non-trivial to implement. The goal of hw is that as long as you don't use the PCI features, it can be used on a legacy model 5150 IBM PC. It should not grow too big to comfortably fit on a 360KB floppy, so I am hesitant to add a DOS extender to it. I might resort to using the "extended memory copy" service provided by the AT (+later) BIOS, and hope that they do a proper WORD and/or DWORD access, but I'm not convinced that call does so in all cases.

[karcherm]

I just checked a random BIOS implementation: INT 15h, AH=87h does not allow byte access, so it seems inappropriate for accessing byte registers in MMIO areas. Too bad. At least, that implementation (Award 4.51) can be used for word and doubleword access without issues.