Tejun Heo wrote:
Alan Cox wrote:
polling for media change which involves reading maybe a few tens of
bytes. The overhead of doing those using PIO wouldn't be too much more
than the cost of writing CDBs out. It would help more if we can cut
down the number of commands used for testing media changed event (on my
to do list).
Actually the overhead is foul on some laptops as the command byte write
wakes up the controller, which then whirrs away for a bit recovering its
status before deciding to give us an answer.
Yeah, but that happens whether DMA is used or not. Probably what's
needed is disabling media presence polling according to power profile.
Does module parameter / sysfs node sound good enough to you?
You mean like the existing "dma" one we already have which lets you turn
on/off atapi DMA and could be extended with another bit so we went from
1 - disk
2 - cd
4 - cf
to
1 - disk
2 - cd (basic commands)
4 - cf
8 - cd (all)
(The idea being that its ordered so troubleshooting almost always comes
down to 1,3 - or 1,3,7 with this). So we have 99.9% of this
Basically, yes but I think it would be nice to be able to change the
value on the fly.
It would also be nice to change it per-device rather than globally...
Jeff
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