Re: Devices without power management support

[mlelstv%serpens.de@localhost (Michael van Elst)]

paul%whooppee.com@localhost (Paul Goyette) writes:

>Don't forget to deregister the device if the xxx_attach() later exits...

I think the point was to not do this, so that a failed attach doesn't
prevent the system from entering sleep mode.

Here, calling pmf_register first on attachment is then required,
but then you have to think on how to handle failures of pmf_register.
You wouldn't want the device to fail attachment in that case,
but rather accept that you cannot suspend in that situation.

You also have to think about drivers that are left only partially
configured after a failed attachment. That is already unsafe with
drivers that only do a dummy pmf registration, but what about
hardware that actually needs support routines ? Registering these
for a partially configured driver may not work either. Unregister
again and register dummy routines ?

An easy solution would be to make attach actually fail, autoconf
could then detached the driver immediately and it won't interfere
with pmf.

N.B. if autoconf API is changed, you could also integrate pmf
into cfattach.