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From: Clint on 12 Sep 2006 15:51
Thanks Vetzak.

I'm trying to use the microchip device driver and was hoping to avoid
writing my own (driver code seems to be pretty involved). There
doesn't appear to be a way to switch off selective suspend in the
microchip driver though so I might, in the end, have no choice but to
write my own.

Thanks for the heads up on the tricky stuff with xp.

Clint

Vetzak wrote:
> Your driver decides when the device goes in and out USB selective
> suspend. To do so, your driver has to send down the wait-wake power IRP
> and then the IOCTL_INTERNAL_USB_SUBMIT_IDLE_NOTIFICATION IRP (see ddk
> docs and USB samples driver sources for details on these mechanisms).
>
> If you don't want USB selective suspend, just don't implement it in
> your driver. Also beware of the state of the "remote wake-up enable"
> bit in the USB configuration descriptor. If set, the USBD will activate
> RWU on te device, else it won't. Your driver doesn't send that
> SetFeature, REMOTE_WAKEUP control request.
>
> One more remark: USB selective suspend in WinXP sucks. Examples:
> * The MS information sources are confusing. First they said selective
> suspend wasn't supported for composite devices, afterwards tey said it
> is. In my experience selective suspend doesn't work properly on all
> systems. That's why we converted our composite devices into
> non-composite devices and wrote bus drivers.
> * The power mappings of root hubs are often wrong leading to strange
> behavior after standby and resume (like the system disconnects USB
> device but the driver isn't surprise-removed). Example wrong mapping:
> S0->D0, S1->D2, S2->D3, S3->D2, S3->D3, S4->D2, S5->D3.
> * If you manage to suspend a USB device, and connect a second device to
> the same (root) hub, the selective suspend is cancelled on the first
> one. So no selective suspend if 2 or more usb device are connected to
> the same (root) hub.
>
> I hope I didn't take the fun away ;-)
>
>
> Clint wrote:
> > Vetzak,
> > I'm using a custom driver.
> >
> > Any ideas how a custom driver indicates it doesn't support selective
> > suspend?
> >
> > Thanks,
> > Clint
> >
> > Vetzak wrote:
> > > Are you using a system driver are a custom driver? A.f.a.i.k. Most
> > > system drivers don't support selective suspend (for example, USB
> > > sticks).

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