On 05/07/2015 11:03 PM, Rafael J. Wysocki wrote: > 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.
Yeah, I tried to make clear that I don't think that this is generally achievable. But in the ChromeOS hardware that I have here, the input event is there for userspace to read when it wakes up. But if there's traction for adding upstream a more generic mechanism that works in a broader range of machines, I'm all for it. Regards, Tomeu -- 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/
