bus_add_device() losing an error return from the probe() method

[Rene Herman <rene.herman@keyaccess.nl>]

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Hi Greg, Takashi.

ALSA moved all ISA drivers over to the platform_driver interface in
2.6.16, using this code structure in the module_inits:

    cards = 0;
    for (i = 0; i < SNDRV_CARDS; i++) {
	  struct platform_device *device;
	  device = platform_device_register_simple(
			SND_FOO_DRIVER, i, NULL, 0);
	  if (IS_ERR(device)) {
		  err = PTR_ERR(device);
		  goto errout;
	  }
	  devices[i] = device;
	  cards++;
    }
    if (!cards) {
	  printk(KERN_ERR "FOO soundcard not found or device busy\n");
	  err = -ENODEV;
	  goto errout;
    }
    return 0;
errout:
    snd_foo_unregister_all();
    return err;

Unfortunately, the snd_foo_unregister_all() part here is unreachable
under normal circumstances, since platform_device_register_simple()
returns !IS_ERR, regardless of what the driver probe method returned.
The driver then never fails to load, even when no cards were found.

An error return from the driver probe() method is carried up through
device_attach, but is then dropped on the floor in bus_add_device(). If
I apply the attached patch, things work as I (and ALSA it seems) expect.
Is it correct?

(the printk still isn't reached, but see next message for that).

Rene.



[-- Attachment #2: bus_add_device.diff --]
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Index: local/drivers/base/bus.c
===================================================================
--- local.orig/drivers/base/bus.c	2006-02-27 19:22:08.000000000 +0100
+++ local/drivers/base/bus.c	2006-03-24 04:27:02.000000000 +0100
@@ -363,19 +363,21 @@ static void device_remove_attrs(struct b
 int bus_add_device(struct device * dev)
 {
 	struct bus_type * bus = get_bus(dev->bus);
-	int error = 0;
+	int error;
 
 	if (bus) {
 		pr_debug("bus %s: add device %s\n", bus->name, dev->bus_id);
-		device_attach(dev);
+		error = device_attach(dev);
+		if (error < 0)
+			return error;
 		klist_add_tail(&dev->knode_bus, &bus->klist_devices);
 		error = device_add_attrs(bus, dev);
-		if (!error) {
-			sysfs_create_link(&bus->devices.kobj, &dev->kobj, dev->bus_id);
-			sysfs_create_link(&dev->kobj, &dev->bus->subsys.kset.kobj, "bus");
-		}
+		if (error)
+			return error;
+		sysfs_create_link(&bus->devices.kobj, &dev->kobj, dev->bus_id);
+		sysfs_create_link(&dev->kobj, &dev->bus->subsys.kset.kobj, "bus");
 	}
-	return error;
+	return 0;
 }
 
 /**