ARM: 8524/1: driver cohandle -EPROBE_DEFER from bus_type.match()

Allow implementations of the match() callback in struct bus_type to
return errors and if it's -EPROBE_DEFER then queue the device for
deferred probing.

This is useful to buses such as AMBA in which devices are registered
before their matching information can be retrieved from the HW
(typically because a clock driver hasn't probed yet).

[changed if-else code structure, adjusted documentation to match the code,
extended comments]

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/device.h b/include/linux/device.h
index 6d6f1fec092f..8f2ec813d215 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -70,8 +70,11 @@ extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
  * @dev_groups: Default attributes of the devices on the bus.
  * @drv_groups: Default attributes of the device drivers on the bus.
  * @match:      Called, perhaps multiple times, whenever a new device or driver
- *              is added for this bus. It should return a nonzero value if the
- *              given device can be handled by the given driver.
+ *              is added for this bus. It should return a positive value if the
+ *              given device can be handled by the given driver and zero
+ *              otherwise. It may also return error code if determining that
+ *              the driver supports the device is not possible. In case of
+ *              -EPROBE_DEFER it will queue the device for deferred probing.
  * @uevent:     Called when a device is added, removed, or a few other things
  *              that generate uevents to add the environment variables.
  * @probe:      Called when a new device or driver add to this bus, and callback