On Friday, June 17, 2016 04:07:38 PM Lukas Wunner wrote:

On Fri, Jun 17, 2016 at 02:54:56PM +0200, Rafael J. Wysocki wrote:

quoted

On Fri, Jun 17, 2016 at 12:36 PM, Lukas Wunner [off-list ref] wrote:

quoted

On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote:

quoted

From: "Rafael J. Wysocki" <redacted>

We also have such a functional dependency for Thunderbolt on Macs:
On resume from system sleep, the PCIe hotplug ports may not resume
before the thunderbolt driver has reestablished the PCI tunnels.
Currently this is enforced by quirk_apple_wait_for_thunderbolt()
in drivers/pci/quirks.c. It would be good if we could represent
this dependency using something like Rafael's approach instead of
open coding it, however one detail in Rafael's patches is problematic:

quoted

New links are added by calling device_link_add() which may happen
either before the consumer device is probed or when probing it, in
which case the caller needs to ensure that the driver of the
supplier device is present and functional and the DEVICE_LINK_PROBE_TIME
flag should be passed to device_link_add() to reflect that.

The thunderbolt driver cannot call device_link_add() before the
PCIe hotplug ports are bound to a driver unless we amend portdrv
to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs
if the thunderbolt driver isn't loaded.

It would therefore be beneficial if device_link_add() can be
called even *after* the consumer is bound.

I don't quite follow.

Who's the provider and who's the consumer here?

thunderbolt.ko is the supplier.

But it binds to the children of the ports that are supposed to be its
consumers?

Why is that even expected to work?

Thanks,
Rafael