On Thu, Jan 31, 2013 at 09:54:51PM +0100, Rafael J. Wysocki wrote: > > > But, again, I'm going to ask why you aren't using the existing cpu / > > > memory / bridge / node devices that we have in the kernel. Please use > > > them, or give me a _really_ good reason why they will not work. > > > > We cannot use the existing system devices or ACPI devices here. During > > hot-plug, ACPI handler sets this shp_device info, so that cpu and memory > > handlers (drivers/cpu.c and mm/memory_hotplug.c) can obtain their target > > device information in a platform-neutral way. During hot-add, we first > > creates an ACPI device node (i.e. device under /sys/bus/acpi/devices), > > but platform-neutral modules cannot use them as they are ACPI-specific. > > But suppose we're smart and have ACPI scan handlers that will create > "physical" device nodes for those devices during the ACPI namespace scan. > Then, the platform-neutral nodes will be able to bind to those "physical" > nodes. Moreover, it should be possible to get a hierarchy of device objects > this way that will reflect all of the dependencies we need to take into > account during hot-add and hot-remove operations. That may not be what we > have today, but I don't see any *fundamental* obstacles preventing us from > using this approach. I would _much_ rather see that be the solution here as I think it is the proper one. > This is already done for PCI host bridges and platform devices and I don't > see why we can't do that for the other types of devices too. I agree. > The only missing piece I see is a way to handle the "eject" problem, i.e. > when we try do eject a device at the top of a subtree and need to tear down > the entire subtree below it, but if that's going to lead to a system crash, > for example, we want to cancel the eject. It seems to me that we'll need some > help from the driver core here. I say do what we always have done here, if the user asked us to tear something down, let it happen as they are the ones that know best :) Seriously, I guess this gets back to the "fail disconnect" idea that the ACPI developers keep harping on. I thought we already resolved this properly by having them implement it in their bus code, no reason the same thing couldn't happen here, right? I don't think the core needs to do anything special, but if so, I'll be glad to review it. thanks, gre k-h -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>