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>

3 files changed, 11 insertions, 1 deletions

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 847f3ca47bb8..c8709c6fdb7c 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -177,10 +177,15 @@ int pci_bus_add_device(struct pci_dev *dev)
         if (retval)
                 return retval;
 
+        dev->match_driver = false;
         retval = device_add(&dev->dev);
         if (retval)
                 return retval;
 
+        dev->match_driver = true;
+        retval = device_attach(&dev->dev);
+        WARN_ON(retval < 0);
+
         dev->is_added = 1;
         pci_proc_attach_device(dev);
         pci_create_sysfs_dev_files(dev);
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index f79cbcd3944b..acdcc3c6ecdd 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -1186,9 +1186,13 @@ pci_dev_driver(const struct pci_dev *dev)
 static int pci_bus_match(struct device *dev, struct device_driver *drv)
 {
         struct pci_dev *pci_dev = to_pci_dev(dev);
-        struct pci_driver *pci_drv = to_pci_driver(drv);
+        struct pci_driver *pci_drv;
         const struct pci_device_id *found_id;
 
+        if (!pci_dev->match_driver)
+                return 0;
+
+        pci_drv = to_pci_driver(drv);
         found_id = pci_match_device(pci_drv, pci_dev);
         if (found_id)
                 return 1;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 907b455ab603..8ee7e4e46539 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -286,6 +286,7 @@ struct pci_dev {
         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 */