于 2012/9/23 3:54, Rafael J. Wysocki 写道:
On Friday, September 21, 2012, Peter Stuge wrote:
Sarah Sharp wrote:
If userspace really wants the port off (e.g. to disconnect and
reconnect a misbehaving device), then it can set the sysfs file
to off.
And unless all ganged ports are also off it will fail. Userspace will
want to know about that, and why, along with a reference that can be
matched against the list of ganged sets of ports.
Ah, right. Yes, we should probably add some dmesg info lines about
why we can't turn off a port right now.
dmesg isn't very programmable. Maybe ioctl after all? Trust me that I
don't have a preference, it's just that I don't know how sysfs could
report back the relevant failure info in a race-free way.
Well, we actually need to handle power domains appropriately.
Unfortunately, ACPI doesn't support the power domain concept directly and
tries to kind of hide them behind power resources, but let's face it, they
are what they are.
Some work in that direction has been done in the ARM space, where we have
much more direct access to hardware, and I suppose it may be extended to
things like "ganged sets of ports" (which actually are power domains).
Do you mean arm has used generic pm domain but ACPI has not yet?
We should associate ACPI power resource with generic pm domain.
Has generic pm domain been exposed to usr space? (e.g via sysfs)
Thanks,
Rafael
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Best regards
Tianyu Lan
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