Hi all,
I'm creating a hardware platform and I want to make a platform device
hot-pluggable using ACPI. The SoC I'm using (AMD A11xx) has ethernet
on-board, and the main board has a plug-in card which contains a media
converter and the actual network media jack. When the plug-in card is
present I want the ethernet device to be shown in tools like ifconfig
(-a), and when it's not present I want the ethernet device to not be shown.
In reading the spec, I feel like this could be implemented like a
docking station or port replicator and that I should be able to make an
ACPI device which is a dock (containing _DCK) and have my ethernet
device be an ejection-dependent device (_EJD) of the dock, much like the
example in section 6.3.2 of the ACPI spec.
When I do this though, it doesn't work. In the device removal case, the
execution in the kernel goes through dock_notify() and
hot_remove_dock_devices() which calls dock_hotplug_event() which fails
because adev->hp is NULL, as there is no hotplug context. This makes
some sense because the ethernet IP block on the SoC is memory-mapped and
not capable of being hot-plugged.
My naive ideas about this are that even without a hotplug context, if
the ACPI reports the device to be gone (and not to be used), that
device_release_driver() could be called on each physical node in
adev->physical_node_list, causing the driver(s) to be unloaded.
I've also tried doing this without using a docking station device[1],
but the same things ultimately happen. Without a hotplug context,
nothing happens to the physical device.
One thing that's not clear to me is whether a _DCK docking station
Device is valid if it's not under a PCI node. The spec doesn't say this,
but all the examples I can find in ACPI documents are this way.
Is there a way to do what I'm wanting to do that I'm missing, or am I
completely misunderstanding how this works? Unfortunately the spec is
ambiguous and real life examples are hard to come by.
Thanks for any help,
Alan.
[1] This second method is where the Notify() is called for the ethernet
device itself (rather than using a dock device) and an _STA in the
ethernet device returns that it's not present. I've seen this in one
example.
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