>I've written a working bootloader, and part of its task is
>to scan the PCI bus and allocate memory. There are two bits
>per device, indicating whther or not th device needs I/O
>and/or Memory access. There are straightforward to set up.
>However, there is a this bit, to decide whether or not
>Bus-Master access is required: how do I determine whether a
>certain slot requires this access, so that I know whether to
>set/clear this bit?

Just always set it to 1.  If a device isn't busmaster capable it will 
hardwire this bit to zero and you won't be able to write it.  That bit is just 
there to prevent devices from going off and doing busmaster operations when 
you don't want them to.

p.