Mark Lord wrote:
Tejun Heo wrote:
Alan Cox wrote:
..
Because we can't use DMA uniformly, I went the other way and tried to
use PIO uniformly. Another important point is that the other OS which
is probably the only platform most ATAPI device vendors test against use
PIO for these commands.
- Control over the DMA/PIO strategy belongs with the driver. If we mess
that up it will cost us dearly later.
And I don't get what we'll lose. Care to deliberate?
..
Mmmm.. so what happens with the various controllers that can do PIO
using host-DMA and host-queuing ? Dropping to *real* PIO mode can
be quite expensive on those, especially when the channel is shared
with a hard disk.
..
Or, for that matter, shared with a port multiplier and several other devices ?
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