Wonky PS2-USB converter issues...

Wonky PS2-USB converter issues...

[Valdis Kletnieks]

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Quite some time ago, I posted about a problematic PS2-USB converter
that I used to connect an old PS2-connector keyboard to my laptop
dock, where the keyboard wouldn't be recognized at boot unless
I unplugged and reconnected it.

Well, I've recently figured out (partly by obtaining a converter
from a different vendor) that the converters both work correctly
when plugged into a USB port that's physically on my Dell Latitude
laptop - but they have issues and require a reconnect cycle when
plugged into the docking station for the laptop. (It took a long time
to figure this out, because *of course* you plug this sort of stuff
into the docking station specifically so you don't have to plug it
in every morning).

So obviously, it isn't the converter that is the problem, but the docking
station is doing "something stupid".  Anybody have suggestions on figuring out
what it's doing wrong?


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Re: Wonky PS2-USB converter issues...

[Greg Kroah-Hartman]

On Wed, Feb 20, 2013 at 05:48:38PM -0500, Valdis Kletnieks wrote:
> Quite some time ago, I posted about a problematic PS2-USB converter
> that I used to connect an old PS2-connector keyboard to my laptop
> dock, where the keyboard wouldn't be recognized at boot unless
> I unplugged and reconnected it.
> 
> Well, I've recently figured out (partly by obtaining a converter
> from a different vendor) that the converters both work correctly
> when plugged into a USB port that's physically on my Dell Latitude
> laptop - but they have issues and require a reconnect cycle when
> plugged into the docking station for the laptop. (It took a long time
> to figure this out, because *of course* you plug this sort of stuff
> into the docking station specifically so you don't have to plug it
> in every morning).
> 
> So obviously, it isn't the converter that is the problem, but the docking
> station is doing "something stupid".  Anybody have suggestions on figuring out
> what it's doing wrong?

PS-2 connectors can not normally handle hotplugging, the protocol
doesn't allow it, and for some unlucky devices, it could actually fry
the motherboard or the PS-2 device.

So that's probably the issue here, the device just doesn't support it,
sorry.

greg k-h

Re: Wonky PS2-USB converter issues...

[Valdis.Kletnieks]

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On Wed, 20 Feb 2013 16:07:49 -0800, Greg Kroah-Hartman said:

> PS-2 connectors can not normally handle hotplugging, the protocol
> doesn't allow it, and for some unlucky devices, it could actually fry
> the motherboard or the PS-2 device.
>
> So that's probably the issue here, the device just doesn't support it,
> sorry.

You mis-understood the problem.

This works:

PS/2 keyboard plugged into this device:
Bus 006 Device 002: ID 0e8f:0020 GreenAsia Inc. USB to PS/2 Adapter
USB side of device plugged into USB port on the Latitude laptop.
Power up, boot - the keyboard works.

If you plug the USB side of the GreenAsia adapter into a USB slot on
the dock, the keyboard is dead and not recognized by the system.  However,
replugging the USB, or unplug/plug the PS/2 side, and it becomes recognized
and starts working.

This tells me that the dock is doing something busted with USB that the laptop
does correctly, and not enumerating devices until something happens to whack it
upside the head. I was hoping to identify it and maybe quirk it.


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Re: Wonky PS2-USB converter issues...

[Alan Stern]

On Wed, 20 Feb 2013 Valdis.Kletnieks@vt.edu wrote:

> On Wed, 20 Feb 2013 16:07:49 -0800, Greg Kroah-Hartman said:
> 
> > PS-2 connectors can not normally handle hotplugging, the protocol
> > doesn't allow it, and for some unlucky devices, it could actually fry
> > the motherboard or the PS-2 device.
> >
> > So that's probably the issue here, the device just doesn't support it,
> > sorry.
> 
> You mis-understood the problem.
> 
> This works:
> 
> PS/2 keyboard plugged into this device:
> Bus 006 Device 002: ID 0e8f:0020 GreenAsia Inc. USB to PS/2 Adapter
> USB side of device plugged into USB port on the Latitude laptop.
> Power up, boot - the keyboard works.
> 
> If you plug the USB side of the GreenAsia adapter into a USB slot on
> the dock, the keyboard is dead and not recognized by the system.  However,
> replugging the USB, or unplug/plug the PS/2 side, and it becomes recognized
> and starts working.
> 
> This tells me that the dock is doing something busted with USB that the laptop
> does correctly, and not enumerating devices until something happens to whack it
> upside the head. I was hoping to identify it and maybe quirk it.

What happens if you prevent ehci-hcd from being loaded during boot and 
then load it manually afterward?  Does the keyboard/adapter/dock 
combination work then?

If it doesn't, try recording a usbmon trace.

Alan Stern