Re: USB resume guarantees

On Sun, 11 Nov 2007 19:14:41 -0800, David Brownell wrote:
> On Sunday 11 November 2007, Tilman Schmidt wrote:
>> While trying to add suspend/resume support to the USB drivers I
>> maintain, I came across the following unexpected sequence of
>> events with kernel 2.6.24-rc2:
>> 
>> - I request suspend to disk by doing
>>   echo shutdown > /sys/power/disk ; echo disk > /sys/power/state
>> 
>> - My driver's suspend method is called, which uses
>>   tasklet_disable() to prevent a tasklet from resubmitting URBs.
> 
> It should also make sure no URBs are pending.

Sure, it does that too. Sorry for not mentioning it.

>> - My driver's disconnect method is called. *Not* the resume
>>   method, *not* the reset_resume method, *just* the disconnect
>>   method.
> 
> Which is perfectly fine.  If someone disconnected the device
> while the system was suspended, that's what would happen.

Ok, thanks for clearing that up. I'll adapt my drivers' suspend
logic accordingly.

>> From reading Documentation/usb/power-management.txt I gathered
>> the impression that suspend and resume/reset_resume calls would
>> be paired,
> 
> In the normal case, yes.  (Though I don't think I've doe
> more than skim that text ...)

I'll translate "in the normal case" to "not necessarily" for my
purposes. :-)

Thanks,
Tilman

-- 
Tilman Schmidt                    E-Mail: [email protected]
Bonn, Germany
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