PCI: Skip attaching driver in device_add()

We want to add PCI devices to the device tree as early as possible but
delay attaching drivers.

device_add() adds a device to the device hierarchy and (via
device_attach()) attaches a matching driver and calls its .probe() method.
We want to separate adding the device to the hierarchy from attaching the
driver.

This patch does that by adding "match_driver" in struct pci_dev.  When
false, we return failure from pci_bus_match(), which makes device_attach()
believe there's no matching driver.

Later, we set "match_driver = true" and call device_attach() again, which
now attaches the driver and calls its .probe() method.

[bhelgaas: changelog, explicitly init dev->match_driver,
fold device_attach() call into pci_bus_add_device()]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 907b455..8ee7e4e 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -286,6 +286,7 @@
 	unsigned int	irq;
 	struct resource resource[DEVICE_COUNT_RESOURCE]; /* I/O and memory regions + expansion ROMs */
 
+	bool match_driver;		/* Skip attaching driver */
 	/* These fields are used by common fixups */
 	unsigned int	transparent:1;	/* Transparent PCI bridge */
 	unsigned int	multifunction:1;/* Part of multi-function device */