Merge branch 'dynamic_sg' into rdma.git for-next

From Maor Gottlieb says:

====================
This series extends __sg_alloc_table_from_pages to allow chaining of new
pages to an already initialized SG table.

This allows for drivers to utilize the optimization of merging contiguous
pages without a need to pre allocate all the pages and hold them in a very
large temporary buffer prior to the call to SG table initialization.

The last patch changes the Infiniband core to use the new API. It removes
duplicate functionality from the code and benefits from the optimization
of allocating dynamic SG table from pages.

In huge pages system of 2MB page size, without this change, the SG table
would contain x512 SG entries.
====================

* branch 'dynamic_sg':
  RDMA/umem: Move to allocate SG table from pages
  lib/scatterlist: Add support in dynamic allocation of SG table from pages
  tools/testing/scatterlist: Show errors in human readable form
  tools/testing/scatterlist: Rejuvenate bit-rotten test

1 files changed, 34 insertions, 16 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 7e73e989645b..b351962279e4 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -269,8 +269,30 @@ static int usb_probe_device(struct device *dev)
 	if (error)
 		return error;
 
+	/* Probe the USB device with the driver in hand, but only
+	 * defer to a generic driver in case the current USB
+	 * device driver has an id_table or a match function; i.e.,
+	 * when the device driver was explicitly matched against
+	 * a device.
+	 *
+	 * If the device driver does not have either of these,
+	 * then we assume that it can bind to any device and is
+	 * not truly a more specialized/non-generic driver, so a
+	 * return value of -ENODEV should not force the device
+	 * to be handled by the generic USB driver, as there
+	 * can still be another, more specialized, device driver.
+	 *
+	 * This accommodates the usbip driver.
+	 *
+	 * TODO: What if, in the future, there are multiple
+	 * specialized USB device drivers for a particular device?
+	 * In such cases, there is a need to try all matching
+	 * specialised device drivers prior to setting the
+	 * use_generic_driver bit.
+	 */
 	error = udriver->probe(udev);
-	if (error == -ENODEV && udriver != &usb_generic_driver) {
+	if (error == -ENODEV && udriver != &usb_generic_driver &&
+	    (udriver->id_table || udriver->match)) {
 		udev->use_generic_driver = 1;
 		return -EPROBE_DEFER;
 	}
@@ -831,14 +853,17 @@ static int usb_device_match(struct device *dev, struct device_driver *drv)
 		udev = to_usb_device(dev);
 		udrv = to_usb_device_driver(drv);
 
-		if (udrv->id_table &&
-		    usb_device_match_id(udev, udrv->id_table) != NULL) {
-			return 1;
-		}
+		if (udrv->id_table)
+			return usb_device_match_id(udev, udrv->id_table) != NULL;
 
 		if (udrv->match)
 			return udrv->match(udev);
-		return 0;
+
+		/* If the device driver under consideration does not have a
+		 * id_table or a match function, then let the driver's probe
+		 * function decide.
+		 */
+		return 1;
 
 	} else if (is_usb_interface(dev)) {
 		struct usb_interface *intf;
@@ -905,26 +930,19 @@ static int usb_uevent(struct device *dev, struct kobj_uevent_env *env)
 	return 0;
 }
 
-static bool is_dev_usb_generic_driver(struct device *dev)
-{
-	struct usb_device_driver *udd = dev->driver ?
-		to_usb_device_driver(dev->driver) : NULL;
-
-	return udd == &usb_generic_driver;
-}
-
 static int __usb_bus_reprobe_drivers(struct device *dev, void *data)
 {
 	struct usb_device_driver *new_udriver = data;
 	struct usb_device *udev;
 	int ret;
 
-	if (!is_dev_usb_generic_driver(dev))
+	/* Don't reprobe if current driver isn't usb_generic_driver */
+	if (dev->driver != &usb_generic_driver.drvwrap.driver)
 		return 0;
 
 	udev = to_usb_device(dev);
 	if (usb_device_match_id(udev, new_udriver->id_table) == NULL &&
-	    (!new_udriver->match || new_udriver->match(udev) != 0))
+	    (!new_udriver->match || new_udriver->match(udev) == 0))
 		return 0;
 
 	ret = device_reprobe(dev);