On Wed, Dec 12, 2012 at 08:37:44PM -0700, Toshi Kani wrote: > On Wed, 2012-12-12 at 16:55 -0800, Greg KH wrote: > > On Wed, Dec 12, 2012 at 05:39:36PM -0700, Toshi Kani wrote: > > > On Wed, 2012-12-12 at 15:56 -0800, Greg KH wrote: > > > > On Wed, Dec 12, 2012 at 04:17:12PM -0700, Toshi Kani wrote: > > > > > This patchset is an initial prototype of proposed hot-plug framework > > > > > for design review. The hot-plug framework is designed to provide > > > > > the common framework for hot-plugging and online/offline operations > > > > > of system devices, such as CPU, Memory and Node. While this patchset > > > > > only supports ACPI-based hot-plug operations, the framework itself is > > > > > designed to be platform-neural and can support other FW architectures > > > > > as necessary. > > > > > > > > > > The patchset has not been fully tested yet, esp. for memory hot-plug. > > > > > Any help for testing will be very appreciated since my test setup > > > > > is limited. > > > > > > > > > > The patchset is based on the linux-next branch of linux-pm.git tree. > > > > > > > > > > Overview of the Framework > > > > > ========================= > > > > > > > > <snip> > > > > > > > > Why all the new framework, doesn't the existing bus infrastructure > > > > provide everything you need here? Shouldn't you just be putting your > > > > cpus and memory sticks on a bus and handle stuff that way? What makes > > > > these types of devices so unique from all other devices that Linux has > > > > been handling in a dynamic manner (i.e. hotplugging them) for many many > > > > years? > > > > > > > > Why are you reinventing the wheel? > > > > > > Good question. Yes, USB and PCI hotplug operate based on their bus > > > structures. USB and PCI cards only work under USB and PCI bus > > > controllers. So, their framework can be composed within the bus > > > structures as you pointed out. > > > > > > However, system devices such CPU and memory do not have their standard > > > bus. ACPI allows these system devices to be enumerated, but it does not > > > make ACPI as the HW bus hierarchy for CPU and memory, unlike PCI and > > > USB. Therefore, CPU and memory modules manage CPU and memory outside of > > > ACPI. This makes sense because CPU and memory can be used without ACPI. > > > > > > This leads us an issue when we try to manage system device hotplug > > > within ACPI, because ACPI does not control everything. This patchset > > > provides a common hotplug framework for system devices, which both ACPI > > > and non-ACPI modules (i.e. CPU and memory modules) can participate and > > > are coordinated for their hotplug operations. This is analogous to the > > > boot-up sequence, which ACPI and non-ACPI modules can participate to > > > enable CPU and memory. > > > > Then create a "virtual" bus and put the devices you wish to control on > > that. That is what the "system bus" devices were supposed to be, it's > > about time someone took that code and got it all working properly in > > this way, that is why it was created oh so long ago. > > It may be the ideal, but it will take us great effort to make such > things to happen based on where we are now. It is going to be a long > way. I believe the first step is to make the boot-up flow and hot-plug > flow consistent for system devices. This is what this patchset is > trying to do. If you use the system "bus" for this, the "flow" will be identical, that is what the driver core provides for you. I don't see why you need to implement something that sits next to it and not just use what we already have here. thanks, greg 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>