Re: [PATCH] Fix OTG HNP for hub.c (USB OTG HNP (can you find any other appropriate TLAs?)

* Felipe Balbi <[email protected]> [070529 16:34]:
> <snip>
>
>> > The behavioral difference would be that WHEN ("not 'IF'")
>> > the whitelist (which is very easily checked against product
>> > documentation) diverges from the list of configured drivers
>> > (no easy way to crosscheck that and docs) things would not
>> > act the same.
>>
>> I guess HNP should be offered for peripherals even if not
>> on whitelist, but only peripherals on whitelist (with HNP
>> or not) should be allowed.
>
> Or maybe we run a set_feature (b_hnp_enabled) just before the
> suspend... can we do that dave?? It doesn't seem really correct when
> typing... but...
>
> If I'm not wrong... every device can accept a b_hnp_enable set_feature
> command... if the controller doesn't support it just return a
> "stall".. or something like that... so... we could just forget about
> the whitelist for now.. can't we?
>
> If the device supports HNP it will get the b_hnp_enable command and
> after a_host enters in suspend mode... it will try to do HNP (if the
> user wants...)

AFAIK, all OTG devices need to support b_hnp_enable, but it's just
a way to tell it that host supports HNP, it does not mean HNP should
enabled. Enabling HNP should be done by the user on the b-device.

>> > This is more or less what you were trying to achieve,
>> > yes?  But it leads to surprising behavior in cases
>> > like:
>> >
>> >    * hook up non-OTG peripheral #1 ... acts just
>> >      the way you'd normally expect
>> >
>> >    * hook up OTG peripheral #2 ... surprise!  it
>> >      refuses to act as a peripheral at first.
>> >
>> > The "principle of least astonishment" argues that
>> > the "peripheral #1" model should be followed for
>> > as long as possible.  Customer service calls would
>> > be a lot simpler too...
>>
>> Yeh I guess in that case it needs to wait for autosuspend
>> until #1 is done.
>>
>> But if #2 is not on whitelist and can do HNP, then
>> it just gets rejected and never gets it's HNP opportunity.
>>
>> Hmmm...

I guess the non-whitelisted b-device should sit waiting for HNP
mode start when the host autosuspend suspends the bus?

Tony

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