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, 22 insertions, 2 deletions

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index c4da2df62e02..16688f50729c 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -560,6 +560,7 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
         struct device_attach_data *data = _data;
         struct device *dev = data->dev;
         bool async_allowed;
+        int ret;
 
         /*
          * Check if device has already been claimed. This may
@@ -570,8 +571,17 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
         if (dev->driver)
                 return -EBUSY;
 
-        if (!driver_match_device(drv, dev))
+        ret = driver_match_device(drv, dev);
+        if (ret == 0) {
+                /* no match */
                 return 0;
+        } else if (ret == -EPROBE_DEFER) {
+                dev_dbg(dev, "Device match requests probe deferral\n");
+                driver_deferred_probe_add(dev);
+        } else if (ret < 0) {
+                dev_dbg(dev, "Bus failed to match device: %d", ret);
+                return ret;
+        } /* ret > 0 means positive match */
 
         async_allowed = driver_allows_async_probing(drv);
 
@@ -691,6 +701,7 @@ void device_initial_probe(struct device *dev)
 static int __driver_attach(struct device *dev, void *data)
 {
         struct device_driver *drv = data;
+        int ret;
 
         /*
          * Lock device and try to bind to it. We drop the error
@@ -702,8 +713,17 @@ static int __driver_attach(struct device *dev, void *data)
          * is an error.
          */
 
-        if (!driver_match_device(drv, dev))
+        ret = driver_match_device(drv, dev);
+        if (ret == 0) {
+                /* no match */
                 return 0;
+        } else if (ret == -EPROBE_DEFER) {
+                dev_dbg(dev, "Device match requests probe deferral\n");
+                driver_deferred_probe_add(dev);
+        } else if (ret < 0) {
+                dev_dbg(dev, "Bus failed to match device: %d", ret);
+                return ret;
+        } /* ret > 0 means positive match */
 
         if (dev->parent)        /* Needed for USB */
                 device_lock(dev->parent);