[PATCH v3] driver core: Don't probe devices after bus_type.match() probe deferral

[Isaac J. Manjarres]

Both __device_attach_driver() and __driver_attach() check the return
code of the bus_type.match() function to see if the device needs to be
added to the deferred probe list. After adding the device to the list,
the logic attempts to bind the device to the driver anyway, as if the
device had matched with the driver, which is not correct.

If __device_attach_driver() detects that the device in question is not
ready to match with a driver on the bus, then it doesn't make sense for
the device to attempt to bind with the current driver or continue
attempting to match with any of the other drivers on the bus. So, update
the logic in __device_attach_driver() to reflect this.

If __driver_attach() detects that a driver tried to match with a device
that is not ready to match yet, then the driver should not attempt to bind
with the device. However, the driver can still attempt to match and bind
with other devices on the bus, as drivers can be bound to multiple
devices. So, update the logic in __driver_attach() to reflect this.

Cc: stable@xxxxxxxxxxxxxxx
Cc: Saravana Kannan <saravanak@xxxxxxxxxx>
Fixes: 656b8035b0ee ("ARM: 8524/1: driver cohandle -EPROBE_DEFER from bus_type.match()")
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@xxxxxxxxxx>
Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Reviewed-by: Saravana Kannan <saravanak@xxxxxxxxxx>
---
 drivers/base/dd.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

v1 -> v2:
- Fixed the logic in __driver_attach() to allow a driver to continue
  attempting to match and bind with devices in case of any error, not
  just probe deferral.

v2 -> v3:
- Restored the patch back to v1.
- Added Guenter's Tested-by tag.
- Added Saravana's Reviewed-by tag.
- Cc'd stable@xxxxxxxxxxxxxxx

Greg,

This is the final version of this patch. Can you please pick this up?

Thanks,
Isaac

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 70f79fc71539..90b31fb141a5 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -881,6 +881,11 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
 		dev_dbg(dev, "Device match requests probe deferral\n");
 		dev->can_match = true;
 		driver_deferred_probe_add(dev);
+		/*
+		 * Device can't match with a driver right now, so don't attempt
+		 * to match or bind with other drivers on the bus.
+		 */
+		return ret;
 	} else if (ret < 0) {
 		dev_dbg(dev, "Bus failed to match device: %d\n", ret);
 		return ret;
@@ -1120,6 +1125,11 @@ static int __driver_attach(struct device *dev, void *data)
 		dev_dbg(dev, "Device match requests probe deferral\n");
 		dev->can_match = true;
 		driver_deferred_probe_add(dev);
+		/*
+		 * Driver could not match with device, but may match with
+		 * another device on the bus.
+		 */
+		return 0;
 	} else if (ret < 0) {
 		dev_dbg(dev, "Bus failed to match device: %d\n", ret);
 		return ret;
-- 
2.37.1.595.g718a3a8f04-goog