That's debatable, but never mind.
"Don't autosuspend" _is_ a reasonable default policy. It's what Linux
has been doing all along.
No it doesn't. If the kernel fails to provide the mechanism there's
nothing that userspace can do about it anyway. If the kernel does
provide the mechanism and userspace ignores it, then things continue to
work the same as they always have.
It's not analogous. Autosuspend involves setting an idle-delay time,
which depends on the type of device and how it is being used. DMA
doesn't involve anything like that.
But forget about the delay for the moment. If there were a high
percentage of disk drives which would fail when DMA was enabled, then
yes, the decision should be left to userspace. If the percentage is
low enough (and shrinking as vendors become more clueful) then moving
the decision into the kernel is acceptable. At the moment USB
autosuspend is not in this position, as we have learned painfully.
This isn't a question of not being able to boot, like the udev fiasco;
this is a question of saving a few watts of power. While it may be
important for laptop users, it is not critical.
Alan Stern
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