[ixp1200] DMA transfers to host?

Hi. I would like to know how to send data from the ENP-2505s sdram to the host disk. I read from the archive that it is possible to communicate between different pci devices, but I need more information on the subject. What exactly does the pci_dma instruction do? Can I use this to send data to the host? How can I fetch data from the host? -- Øyvind Hvamstad