On Mon, 3 Dec 2012, Andy Green wrote:
> Unless someone NAKs it for sure already (if you're already sure you're
> going to, please do so to avoid wasting time), I'll issue a try#2 of my
> code later which demonstrates what I mean. At least I guess it's useful
> for comparative purposes.
Before you go writing a whole lot more code, we should discuss the
basics a bit more clearly. There are several unsettled issues here:
1. Should the LAN95xx stuff be associated with the ehci-omap.0's
driver or with the hub port? The port would be more flexible,
offering the ability to turn the power off and on while the
system is running without affecting anything else. But the
port code is currently in flux, which could cause this new
addition to be delayed.
(On the other hand, since the LAN95xx is the only thing
connected to the root hub, it could be powered off and on by
unbinding the ehci-omap.0 device from its driver and rebinding
it.)
2. If we do choose the port, do we want to identify it by matching
against a device name string or by matching a sequence of port
numbers (in this case, a length-1 sequence)? The port numbers
are fixed by the board design, whereas the device name strings
might get changed in the future. On the other hand, the port
numbers apply only to USB whereas device names can be used by
any subsystem.
3. Should the matching mechanism go into the device core or into
the USB port code? (This is related to the previous question.)
4. Should this be implemented simply as a regulator (or a pair of
regulators)? Or should it be generalized to some sort of PM
domain thing? The generic_pm_domain structure defined in
include/linux/pm_domain.h seems like overkill, but maybe it's
the most appropriate thing to use.
Until we decide on the answers to these questions, there's no point
writing detailed patches.
Alan Stern
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