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SubjectRe: IDE changes that affect upper layer drivers
On 6 Jan 2003, Alan Cox wrote:

I really hope this isn't going to be a replay of "new modules" where
major stuff gets broken. I would really not like to contemplate turning
off DMA until all the drivers get rewritten. Going without modules costs
only a bit of memory, going without DMA costs a LOT of CPU with some

> I'm about to enable the vmda logic for non disk drivers. That means IDE
> tape, scsi, cd and friends need updating to follow the new rules
> Before it was simply:
> ->dma = 1 - do DMA
> Some devices and a lot of upcoming ones support DMA to the host while
> doing PIO to the device "Virtual DMA". That means the drivers now
> need to do
> 0 X PIO
> 1 0 Issue PIO commands, set up for DMA xfers
> 1 1 Issue DMA commands, set up for DMA xfers
> Alan

Wishing you the best of luck with this one...

bill davidsen <>
CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

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