Re: current state of USB SUSPEND?
Oliver Neukum <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
Am Freitag, 20. April 2007 13:02 schrieb Sven Anders:
> David Brownell schrieb:
> > On Friday 20 April 2007 12:53 am, Oliver Neukum wrote:
> >> Am Freitag, 20. April 2007 09:46 schrieb Sven Anders:
> >>> Oliver Neukum schrieb:
> >>>> Am Mittwoch, 18. April 2007 13:22 schrieb Jeroen Janssen:
> >>>>> Hello,
> >>>>>
> >>>>> I noticed several recent USB SUSPEND related patches on this
> >>>>> mailinglist and I was
> >>>>> wondering if someone could tell me what the current state of USB SUSPEND is.
> >>>> It basically works, but is supported in few drivers.
> >>> Is there a list of the supported drivers?
> >> As of 2.6.21-rc7: hub, usblp, kaweth, skeleton
> >
> > Mr. Grep reports more:
> >
> > input/{appletouch,hid-core}.c
> > misc/usbtest.c
> > net/{asix,cdc_ether,cdc_subset,dm9601,gl620a,mcs7830,net1080,
> > pegasus,plusb,rndis_host,rtl8150,zaurus}.c
> > storage/usb.c
> >
> > The HID stuff even handles remote wakeup...
> >
> > ISTR the usb audio driver needs suspend()/resume() methods too.
>
> Basically does it mean, if the USB driver has the suspend()/resume() methods
> implemented, the autosuspend feature is supported?
No. These methods are a necessary prerequisite to do autosuspend.
They are not sufficient to do autosuspend. They do allow a system wide
suspend.
> I'm interested in adding support for 'autosuspend' to the appletouch driver.
> It has the suspend()/resume() methods. The driver is using a USB interrupt
> method and will get constantly data from the touchpad hardware.
> How does the autosuspend framework know, that it can suspend it, if it is
> constantly sending it's data?
It doesn't. How to do autosuspend for input devices is tricky. The solution
is currently getting the finishing touches.
> The driver could detect, if there is no finger on the pad and can release
> the driver for suspending, is this implemented or does it generally work
> some other way?
If you can reliably detect the finger leaving the pad and do a remote wakeup
if it comes back, you've got a working strategy for autosuspend. Is that
the case?
Regards
Oliver
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