I'm trying to write an IDE driver with busmaster DMA support.
My problem is that I can't get the right controller registers addresses.
In the IDE BusMaster DMA specification :
"The control registers for the controller are allocated via the
devices Base Address register at offset 0x20 in PCI configuration
space."
If I read the word at offset 0x20 in the PCI configuration space, I get
0xc001. But if I boot qemu with a linux live-cd, it tells me that BM-DMA
is at 0xc000
Do I have to init the PCI IDE controller or something ?
Bit 0 encodes if the registers are in IO (1) or in memory (0) space.
You get the IO base address by using a 0xfffffffe mask.
For memory space the mask is 0xfffffff0, the low four bits encode
a few memory properties (prefetch, 32-bit vs. 64-bit memory addresses).
See the PCI spec for more details. Or for example the PCI_BASE_* defines here:
http://cvs.opensolaris.org/source/xref/usr/src/uts/common/sys/pci.h#519