On Mon, 2013-02-04 at 20:45 +0100, Rafael J. Wysocki wrote: > On Monday, February 04, 2013 09:46:18 AM Toshi Kani wrote: > > On Mon, 2013-02-04 at 04:46 -0800, Greg KH wrote: > > > On Sun, Feb 03, 2013 at 05:28:09PM -0700, Toshi Kani wrote: > > > > On Sat, 2013-02-02 at 16:01 +0100, Greg KH wrote: > > > > > On Fri, Feb 01, 2013 at 01:40:10PM -0700, Toshi Kani wrote: > > > > > > On Fri, 2013-02-01 at 07:30 +0000, Greg KH wrote: > > > > > > > On Thu, Jan 31, 2013 at 06:32:18PM -0700, Toshi Kani wrote: > > > > > > > > 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. > > > > > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > > > There are three different approaches suggested for system device > > > > > > > > hot-plug: > > > > > > > > A. Proceed within system device bus scan. > > > > > > > > B. Proceed within ACPI bus scan. > > > > > > > > C. Proceed with a sequence (as a mini-boot). > > > > > > > > > > > > > > > > Option A uses system devices as tokens, option B uses acpi devices as > > > > > > > > tokens, and option C uses resource tables as tokens, for their handlers. > > > > > > > > > > > > > > > > Here is summary of key questions & answers so far. I hope this > > > > > > > > clarifies why I am suggesting option 3. > > > > > > > > > > > > > > > > 1. What are the system devices? > > > > > > > > System devices provide system-wide core computing resources, which are > > > > > > > > essential to compose a computer system. System devices are not > > > > > > > > connected to any particular standard buses. > > > > > > > > > > > > > > Not a problem, lots of devices are not connected to any "particular > > > > > > > standard busses". All this means is that system devices are connected > > > > > > > to the "system" bus, nothing more. > > > > > > > > > > > > Can you give me a few examples of other devices that support hotplug and > > > > > > are not connected to any particular buses? I will investigate them to > > > > > > see how they are managed to support hotplug. > > > > > > > > > > Any device that is attached to any bus in the driver model can be > > > > > hotunplugged from userspace by telling it to be "unbound" from the > > > > > driver controlling it. Try it for any platform device in your system to > > > > > see how it happens. > > > > > > > > The unbind operation, as I understand from you, is to detach a driver > > > > from a device. Yes, unbinding can be done for any devices. It is > > > > however different from hot-plug operation, which unplugs a device. > > > > > > Physically, yes, but to the driver involved, and the driver core, there > > > is no difference. That was one of the primary goals of the driver core > > > creation so many years ago. > > > > > > > Today, the unbind operation to an ACPI cpu/memory devices causes > > > > hot-unplug (offline) operation to them, which is one of the major issues > > > > for us since unbind cannot fail. This patchset addresses this issue by > > > > making the unbind operation of ACPI cpu/memory devices to do the > > > > unbinding only. ACPI drivers no longer control cpu and memory as they > > > > are supposed to be controlled by their drivers, cpu and memory modules. > > > > > > I think that's the problem right there, solve that, please. > > > > We cannot eliminate the ACPI drivers since we have to scan ACPI. But we > > can limit the ACPI drivers to do the scanning stuff only. This is > > precisely the intend of this patchset. The real stuff, removing actual > > devices, is done by the system device drivers/modules. > > In case you haven't realized that yet, the $subject patchset has no future. That's really disappointing, esp. the fact that this basic approach has been proven to work on other OS for years... > Let's just talk about how we can get what we need in more general terms. So, are we heading to an approach of doing everything in ACPI? I am not clear about which direction we have agreed with or disagreed with. As for the eject flag approach, I agree with Greg. Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
