driver core: Flow the return code from ->probe() through to sysfs bind

Currently really_probe() returns 1 on success and 0 if the probe() call
fails. This return code arrangement is designed to be useful for
__device_attach_driver() which is walking the device list and trying every
driver. 0 means to keep trying.

However, it is not useful for the other places that call through to
really_probe() that do actually want to see the probe() return code.

For instance bind_store() would be better to return the actual error code
from the driver's probe method, not discarding it and returning -ENODEV.

Reorganize things so that really_probe() returns the error code from
->probe as a (inverted) positive number, and 0 for successful attach.

With this, __device_attach_driver can ignore the (positive) probe errors,
return 1 to exit the loop for a successful binding and pass on the
other negative errors, while device_driver_attach simplify inverts the
positive errors and returns all errors to the sysfs code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/20210617142218.1877096-4-hch@lst.de
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/base/bus.c

@@ -212,13 +212,9 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,
 	dev = bus_find_device_by_name(bus, NULL, buf);
 	if (dev && driver_match_device(drv, dev)) {
 		err = device_driver_attach(drv, dev);
-
-		if (err > 0) {
+		if (!err) {
 			/* success */
 			err = count;
-		} else if (err == 0) {
-			/* driver didn't accept device */
-			err = -ENODEV;
 		}
 	}
 	put_device(dev);

drivers/base/dd.c

@@ -607,10 +607,10 @@ re_probe:
 	probe_ret = call_driver_probe(dev, drv);
 	if (probe_ret) {
 		/*
-		 * Ignore errors returned by ->probe so that the next driver can
-		 * try its luck.
+		 * Return probe errors as positive values so that the callers
+		 * can distinguish them from other errors.
 		 */
-		ret = 0;
+		ret = -probe_ret;
 		goto probe_failed;
 	}
 
@@ -653,7 +653,6 @@ re_probe:
 		dev->pm_domain->sync(dev);
 
 	driver_bound(dev);
-	ret = 1;
 	pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 		 drv->bus->name, __func__, dev_name(dev), drv->name);
 	goto done;
@@ -746,8 +745,8 @@ EXPORT_SYMBOL_GPL(wait_for_device_probe);
  * @dev: device to try to bind to the driver
  *
  * This function returns -ENODEV if the device is not registered, -EBUSY if it
- * already has a driver, and 1 if the device is bound successfully and 0
- * otherwise.
+ * already has a driver, 0 if the device is bound successfully and a positive
+ * (inverted) error code for failures from the ->probe method.
  *
  * This function must be called with @dev lock held.  When called for a
  * USB interface, @dev->parent lock must be held as well.
@@ -882,7 +881,14 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
 	if (data->check_async && async_allowed != data->want_async)
 		return 0;
 
-	return driver_probe_device(drv, dev);
+	/*
+	 * Ignore errors returned by ->probe so that the next driver can try
+	 * its luck.
+	 */
+	ret = driver_probe_device(drv, dev);
+	if (ret < 0)
+		return ret;
+	return ret == 0;
 }
 
 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
@@ -1038,7 +1044,7 @@ static void __device_driver_unlock(struct device *dev, struct device *parent)
  * @dev: Device to attach it to
  *
  * Manually attach driver to a device. Will acquire both @dev lock and
- * @dev->parent lock if needed.
+ * @dev->parent lock if needed. Returns 0 on success, -ERR on failure.
  */
 int device_driver_attach(struct device_driver *drv, struct device *dev)
 {
@@ -1048,6 +1054,9 @@ int device_driver_attach(struct device_driver *drv, struct device *dev)
 	ret = driver_probe_device(drv, dev);
 	__device_driver_unlock(dev, dev->parent);
 
+	/* also return probe errors as normal negative errnos */
+	if (ret > 0)
+		ret = -ret;
 	return ret;
 }
 
@@ -1114,7 +1123,9 @@ static int __driver_attach(struct device *dev, void *data)
 		return 0;
 	}
 
-	device_driver_attach(drv, dev);
+	__device_driver_lock(dev, dev->parent);
+	driver_probe_device(drv, dev);
+	__device_driver_unlock(dev, dev->parent);
 
 	return 0;
 }