On Wed, 16 Jul 2014, Dmitry Torokhov wrote: > We are not planning on implementing the policy in kernel, that's > indeed task for userspace; but unless we bring in the heavy hammer of > forcibly unbinding drivers, we do not currently have universal > mechanism of quiescing devices.
We sort of do: the ->freeze() callback. But it wasn't intended for this kind of use; drivers may very well expect that userspace will already be frozen when the callback runs. Besides, ->freeze() is supposed to quiesce devices without powering them down, whereas you want to do both. What you're asking for is different from anything the PM subsystem has done before. Given this fact, I don't see any alternatives to adding a new API or repurposing an existing API. Either one would be somewhat painful. For example, we could arrange to invoke ->suspend(). However, since the circumstances would be unusual (userspace is still running, ->prepare() was not called beforehand, ->suspend_irq() won't be called afterward), subsystems and drivers may very well react inappropriately. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
