On Fri, Nov 16, 2007 at 12:01:40AM -0800, Mohammad M Molla wrote: > I am a bit confused by the relation between a DMA controller and > device - (let's say NIC) support of DMA. > > My questions are - > > 1. Is it possible to perform DMA operation on a system without any > central DMA controller? Yes, many PCI devices can do busmaster DMA. Check the output of "lspci -vvv" and look for "BusMaster+". > 2. How are different DMA channels distributed among different devices? Depends on the architecture. The PC architecture has ISA DMA channels which can be used (with many ifs and buts) for a couple of IO mapped devices. > 3. When we program DMA for a device, we program the registers on > the device or on the DMA controller? Depends on the device. For a PCI device, you program the device. How that works is not specified, you have to look it up in the device data sheets. Erik -- They're all fools. Don't worry. Darwin may be slow, but he'll eventually get them. -- Matthew Lammers in alt.sysadmin.recovery
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