Messages in this thread | | | Date | Thu, 28 Aug 2008 13:35:57 -0700 | From | Greg KH <> | Subject | Re: Fwd: Re: [PATCH] USB: add USB test and measurement class driver |
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On Thu, Aug 28, 2008 at 08:22:53PM +0200, Marcel Janssen wrote: > On Thursday 28 August 2008 18:21:09 Greg KH wrote: > > On Thu, Aug 28, 2008 at 11:37:24AM +0200, Marcel Janssen wrote: > > > Hello Greg, > > > > > > I've got me a bit confused there :-) > > > > > > We currently only use the suspend/resume in our device which works on a > > > received request from the PC. > > > Basically sending suspend will make the device enter this mode. When the > > > PC enters this mode, it's also clear it will send a resume when resuming > > > from standby. But, how is this supposed to work when the PC is not in > > > sleep mode.....how will the device wake up ? > > > > It should "automatically" wake up if something happens to it. The USB > > spec calls this out as to how this should work. If the devices don't > > support this, we don't have to add support for it :) > > Actually this is a good point. > > The USB spec mentions that the device should suspend when a constant idle > state is detected for more than 3.0ms. > > I either have not seen that happening before or I missed something when > writing my firmware. I'll keep an eye on my USB analyzer though :-) > Although it's a good thing to keep to the spec, I also believe that in the > case of a test and measurement device suspending the device may be an > unwanted behaviour but perhaps I do misinterpret this part of the spec here. > > Anyway, this is no issue for self-powered devices, which is probably the > majority in this class because most test & measurement devices need a good > power supply and USB just isn't fit for that unless you're able to make a > clean power from that (which is possible of course). > Our device is both USB and self powered, but when in USB powered mode it will > only suspend when the host goes in sleep mode. > > To be honest I would put suspend mode far down on the priority list :-)
Ok, thanks for letting us know, if they are self-powered, this shouldn't be much of an issue. Let's focus on getting the current driver working again :)
thanks,
greg k-h
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