Re: [linux-pm] swsusp regression [Was: 2.6.17-mm1]

[Alan Stern]

On Thu, 22 Jun 2006, Greg KH wrote:

> > There are several possible ways to fix this.  One is to add suspend and 
> > resume routines to the endpoint-device driver.  Another is to change the 
> > code that checks for the children being suspended, to make it check only 
> > for child USB devices and not child endpoints.
> 
> I think it needs to check for _USB_ devices, not just any old device
> that could possibly be attached to the main USB device (as this one is.)
> What's to stop any other struct device to bind here and cause the same
> problem?

In my upcoming patches for USB core suspend improvements, one of the 
changes affects this very piece of code.  Instead of looping over all 
child devices in the driver-model sense, it loops over all interfaces in 
the active configuration, which is all we care about right here.

> Ok, the problem is in verify_suspended(), we are not detecting what type
> of device this is.
> 
> Alan, what are you trying to check for here?  What "bogus requests" were
> you seeing from sysfs that you are trying to filter out?

I didn't write that routine, Dave Brownell did.  It has been there for
ages.  The "bogus requests" are attempts by the user to suspend a USB
device (by writing to /sys/devices/.../power/state) without first
suspending all its children and interfaces.

(This can't happen when doing a global suspend because the PM core 
iterates through the entire device tree.  It matters only for "runtime" or 
"selective" suspend.)

The two easiest ways to fix the problem are:

	Change the code to look through the interfaces in the active
	configuration instead of using device_for_each_child;

or

	Revert your "endpoints are devices" patch until my upcoming
	changes are in place.

Alan Stern

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