On Thursday, June 13, 2013 03:28:59 PM Toshi Kani wrote: > On Thu, 2013-06-13 at 01:23 +0200, Rafael J. Wysocki wrote: > > Hi All, > > > > It turns out that some BIOSes add container device IDs as _CIDs to device > > object that in principle may be matched against the other scan handlers (or > > ACPI drivers, but that's not a problem, because the container scan handler > > can co-exist with an ACPI driver). That's why our recent fix for an issue > > related to the ACPI video driver had to be reverted right before -rc5. > > I am familiar with this firmware, although I no longer have access to > the systems. An SBA device object has _HID with an HP-specific PNPID > and _CID with a generic container PNPID. The _HID allows an OS with the > HP SBA driver (which recognizes the _HID) to enable the SBA's I/O TLB > functionality, while the _CID allows an OS without the HP SBA driver to > boot-up by treating this SBA as a container. The _CID is needed because > some OS skips scanning underneath when it finds an unrecognized object. How cute. > > Although I submitted an alternative fix for that bug, I think the problem > > with the container scan handler possibly matching devices already having > > some other scan handlers attached needs addressing, because we may need to > > use the container hotplug profile for those devices. The following patch > > series is supposed to address it. > > When the HP SBA driver is bound to the SBA object, this driver needs to > handle a hotplug request when it is supported. This is because the I/O > TLB functionality requires its hot-delete operation as well. The > container scan handler can be used only when this driver is bound to the > SBA object as a container and therefore its I/O TLB functionality is not > used. Ah, so in fact those device IDs are kind of mutually exclusive? That is, we only should use the _CID if we don't use the _HID, right? We have a bug there, then, but it probably is bening enough for 3.10 to be left as is. > > [1/5] ACPI / scan: Do not bind ACPI drivers to objects with scan handlers > > (this version shouldn't break the Tony's IA64 HP box the previous one broke) > > [2/5] ACPI / scan: Separate hotplug profiles from scan handlers > > [3/5] ACPI / scan: Add hotplug profile pointer to struct acpi_device > > [4/5] ACPI / scan: Use container hotplug profile for matching device objects > > [5/5] ACPI / ia64 / sba_iommu: Use ACPI scan handler for discovery > > > > Patches [1-4/5] were run on my Toshiba test box and didn't break it, but it > > really doesn't do any ACPI hotplug notifications. > > > > Patch [5/5] is kind of additional, but it wouldn't work correctly without the > > previous ones (to be honest, I haven't tried to compile it yet, but here it > > goes for completness). > > I think we only need patch [5/5] to address the problem. We have > enhanced the match function of scan handlers to match a proper driver > with respect to their priority order, i.e. matching with _HID first and > then with _CIDs. Patch [5/5] should assure that the HP SBA driver is > bound to an SBA object when this driver is configured to the kernel. OK, but then I'd like to apply a modified version of [1/5] that won't check if the scan handler is the container handler, but will just return -EINVAL if any scan handler has been set already. And the changelog of [5/5] needs to be modified slightly. Tony promised me to test those patches on his box, so we'll know for sure in a while. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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
