Re: [linux-usb-devel] Re: The evilness of struct usb_device->auto_pm

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On Friday, 28 September 2007 09:04, Oliver Neukum wrote:
> Am Donnerstag 27 September 2007 schrieb Rafael J. Wysocki:
> > On Thursday, 27 September 2007 21:59, Oliver Neukum wrote:
> > > Am Donnerstag 27 September 2007 schrieb Rafael J. Wysocki:
> > > > On Thursday, 27 September 2007 21:37, Oliver Neukum wrote:
> > > > > Am Donnerstag 27 September 2007 schrieb Rafael J. Wysocki:
> > > > > > > But there's a problem, in that the resume methods don't take a message 
> > > > > > > parameter.  So they wouldn't know whether they were doing a runtime 
> > > > > > > resume or a system resume.
> > > > > > 
> > > > > > This is a general problem with the .resume() routines.
> > > > > > 
> > > > > > If you want to use one for runtime resume, the driver needs to preserve
> > > > > > information allowing it to figure out what kind of resume is going to happen.
> > > > > 
> > > > > How? Suppose you
> > > > > 
> > > > > 1) runtime suspend
> > > > > 2) whole system suspend
> > > > > 3) whole system resume
> > > > > 
> > > > > What kind of resume do you do?
> > > > 
> > > > System resume, I'd guess.
> > > 
> > > How do you know unless resume() tells you to do so?
> > > 
> > > > Anyway, if we are going to stop using the freezer during suspend, the locking
> > > > requirements will probably have to unified between the runtime and system
> > > > suspend.
> > > 
> > > Even so, eg. for storage devices you should unquiesce them in case of runtime
> > > suspend, which makes no sense otherwise.
> > 
> > OK
> > 
> > What exactly would you like to do?
> 
> Put the stuff into struct device and move the autosuspend code into
> driver core.

Well, I thought that it would be nicer if drivers handled autosuspend in a
transparent (from the point of view of the core) way.

Now, it seems to follow from what you're saying that this is not possible in
general, because of USB mass storage devices that need some special handling.

I'm not familiar with the USB code, so can you please tell me how the USB
autosuspend is handled at present and what exactly the problem with that is?

Greetings,
Rafael

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