linux-kernel - Re: A desktop environment[1] kernel wishlist

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Date:	Thu, 07 May 2015 23:03:32 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Chirantan Ekbote <chirantan@...omium.org>,
	Olof Johansson <olof@...om.net>,
	John Stultz <john.stultz@...aro.org>,
	Bastien Nocera <hadess@...ess.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	snanda@...omium.org, Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: A desktop environment[1] kernel wishlist

On Thursday, May 07, 2015 05:54:56 PM One Thousand Gnomes wrote:
> On Tue, 05 May 2015 14:31:26 +0200
> 
> > For example, when you wake up from S3 on ACPI-based systems, the best you
> > can get is what devices have generated the wakeup events, but there's
> > no input available from that (like you won't know which key has been
> > pressed).  You may not get that even.  You may only know what GPEs have
> > caused the wakeup to happen and they may be shared.
> > 
> > For PCI wakeup, the wakeup event may be out of band.  You need to walk
> > the hierarchy and check the PME status bits to identify the wakeup device
> > and then you need to be careful enough not to reset it while putting into
> > D0 for the input data associated with the event to be available.  I'm not
> > sure how many device/driver combinations this actually works for.
> > 
> > For USB wakeup, you get the wakeup event from the controller which may be
> > a PCI device.  Getting to the USB device itself from there requires some
> > work and even then the device may not "remember" what exactly happened.
> > 
> > Further, if you wake up via the PC keyboard from suspend-to-idle, the
> > wakeup key code is not available, the only thing you know is that the
> > interrupts has occured (that may be changed, but it's how the current
> > code works).
> 
> It's probably got to change, otherwise once machines get able to sleep
> between keypresses it's going to suck every time you pause and think for
> a minute then begin typing. Remember display being off for suspend is
> purely a limitation of most current display panels.

Right.

It is just one example, though.

Take a PCI device in D3hot for another one.  It may not even have a buffer
to store input data while in that state.  The only thing it may be able to
do is to signal a PME from it.

Rafael

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