On Thu, Sep 22, 2011 at 7:13 PM, Matthew Garrett [off-list ref] wrote:

We're seeing an increasing number of machines that use acpi
notifications to trigger rescans of devices - for instance, SD readers
that only appear on the PCI bus once a card has been inserted. These
often fail to flag themselves as removable or ejectable, so the acpiphp
core never binds. I think we need to fix this pretty urgently, for PCI
if nothing else.

Can you elaborate on this a bit?  I certainly agree that Prarit's
process hang needs to be fixed, but it sounds like you're talking
about the larger issue of the ACPI core not supporting hotplug.

I think that since the core doesn't do hotplug, we can't deal with
hot-add of any ACPI devices unless we have already loaded a driver
that has hotplug support for that device.  And acpiphp is not really a
"driver," in the sense that it doesn't bind to a specific PNP ID and
there isn't a good way to autoload it.

If we moved most of the notification parts of acpiphp into the core,
maybe that would be a step towards handling these SD readers and
similar devices?