Oliver Neukum wrote:
> Am Mittwoch, 5. Juni 2002 01:46 schrieb David Brownell:
> 
>>>  http://marc.theaimsgroup.com/?l=linux-kernel&m=102320879912115&w=2
>>>  http://marc.theaimsgroup.com/?l=linux-kernel&m=102320879912113&w=2
>>>  http://marc.theaimsgroup.com/?l=linux-kernel&m=102320879912119&w=2
>>
>>By the way, this suggests that USB devices should have two new
>>optional methods in struct usb_driver:
>>
>>  int         (*suspend) (struct usb_device *dev, u32 state, u32 level);
>>  int (*resume) (struct usb_device *dev, u32 level);
>>
>>Currently calls of those names are there, commented out (no
>>infrastructure), and with slightly different syntax (state/level stuff
>>unresolved).
> 
> 
> That sounds reasonable. If you want them optional, you need
> some reasonable defaults.

Today's defaults are that neither method exists, so both are
presumed to succeed.  Trying to change that would make trouble.


>>Seems to me that upcoming USB patches ought to
>>
>>(a) add those two calls
>>(b) add usbcore glue to turn struct device suspend/resume
>>     calls into ones made on usb device drivers
>>(c) teach at least the "hub" driver what to do there ... like
>>     for starters, suspend should disconnect devices when the
>>     power rules mean they won't be suspending.
> 
> 
> No, no, no. You walk the subtree below the pivotal hub
> and tell all devices to suspend into the off state.

No, generic device tree code does that.  Though it's not yet
clear to me how that should map to USB ... the multi-level
suspend() levels need to accomodate some top-down constraints
from USB hubs that aren't going to be able to maintain power
over suspend, but I only noticed a bottom-up model there.

- Dave



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