On Tue 2010-01-26 19:47:45, Rafael J. Wysocki wrote: > On Tuesday 26 January 2010, Pavel Machek wrote: > > On Mon 2010-01-25 22:54:37, Rafael J. Wysocki wrote: > > > On Monday 25 January 2010, Alan Cox wrote: > > > > > > But in that case we should be able to disable the VT switch disable > > > > > > path; we just have to check each driver as it's loaded. > > > > > > > > > > OK, what the right sequence of checks would be in that case and where to place > > > > > them? > > > > > > > > Why are we even driving a vt switch direct from the suspend/resume > > > > logic ? The problem starts there. If it was being handled off the device > > > > suspend/resume method then there wouldn't be a mess to start with ? > > > > > > > > Start at the beginning > > > > > > > > - Why do we switch to arbitarily chosen 'last vt' > > > > - Why isn't vt related suspend/resume handled by the device > > > > > > Well, that was added long ago as a workaround for some problems people > > > reported (presumably). I've never looked at that before, so I can't really > > > tell why someone did it this particular way. > > > > As X drives hardware, it is/was neccessary to get control out of X and > > console switch was convenient. > > > > Note that it needs to happen with userland still active -- before > > freezer. > > Well, that's a bit cumbersome. (which was one of reasons it got special casing). > > And yes, it should be per-driver these days. > > That would have to be done using suspend notifiers and should depend on what > driver actually controls the screen at the moment. And I guess the only case > in which we actually _need_ to do the kernel VT switch is when the hardware > is controlled by X and without KMS. We need vt switch when display is controlled by userland app directly accessing hw. It may or may not be X (svgalib anyone?, gtk-on-framebuffer? qtopia?). Ideally, userspace should explicitely tell us. KD_KERNEL_GRAPHICS console mode? Plus the switch is needed for any graphics app using fbcon -- I do not think we actually save the framebuffer over suspend. (This one should probably be fixed). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
