linux-kernel - Re: [Patch 4/4] Driver core: Don't fail attaching the device if it cannot be bound.

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Date:	Tue, 17 Oct 2006 18:25:36 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Greg K-H <greg@...ah.com>,
	Duncan Sands <duncan.sands@...h.u-psud.fr>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [Patch 4/4] Driver core: Don't fail attaching the device if it
 cannot be bound.

On Tue, 17 Oct 2006 12:04:28 -0400 (EDT),
Alan Stern <stern@...land.harvard.edu> wrote:

> > -int bus_attach_device(struct device * dev)
> > +void bus_attach_device(struct device * dev)
> >  {
> >  	struct bus_type *bus = dev->bus;
> > -	int ret = 0;
> > +	int ret;
> >  
> >  	if (bus) {
> >  		dev->is_registered = 1;
> >  		ret = device_attach(dev);
> > -		if (ret >= 0) {
> > +		BUG_ON(ret < 0);
> > +		if (ret >= 0)
> >  			klist_add_tail(&dev->knode_bus, &bus->klist_devices);
> > -			ret = 0;
> > -		} else
> > +		else
> >  			dev->is_registered = 0;
> 
> It looks odd to test the value of ret when you've just crashed the system 
> if ret < 0.  You probably should change the BUG_ON to a WARN_ON or 
> something similar.

OK, WARN_ON is probably better (but it should never happen anyway).
Updated patch below.



From: Cornelia Huck <cornelia.huck@...ibm.com>

Don't fail bus_attach_device() if the device cannot be bound.

If dev->driver has been specified, reset it to NULL if device_bind_driver()
failed and add the device as an unbound device. As a result, bus_attach_device()
now cannot fail, and we can remove some checking from device_add().

Also remove an unneeded check in bus_rescan_devices_helper().

Signed-off-by: Cornelia Huck <cornelia.huck@...ibm.com>

---
 drivers/base/base.h |    2 +-
 drivers/base/bus.c  |   13 +++++--------
 drivers/base/core.c |    5 +----
 drivers/base/dd.c   |    6 +++++-
 4 files changed, 12 insertions(+), 14 deletions(-)

--- linux-2.6.orig/drivers/base/dd.c
+++ linux-2.6/drivers/base/dd.c
@@ -221,7 +221,7 @@ static int device_probe_drivers(void *da
  *
  *	Returns 1 if the device was bound to a driver;
  *	0 if no matching device was found or multithreaded probing is done;
- *	error code otherwise.
+ *	-ENODEV if the device is not registered.
  *
  *	When called for a USB interface, @dev->parent->sem must be held.
  */
@@ -235,6 +235,10 @@ int device_attach(struct device * dev)
 		ret = device_bind_driver(dev);
 		if (ret == 0)
 			ret = 1;
+		else {
+			dev->driver = NULL;
+			ret = 0;
+		}
 	} else {
 		if (dev->bus->multithread_probe)
 			probe_task = kthread_run(device_probe_drivers, dev,
--- linux-2.6.orig/drivers/base/core.c
+++ linux-2.6/drivers/base/core.c
@@ -479,8 +479,7 @@ int device_add(struct device *dev)
 	if ((error = bus_add_device(dev)))
 		goto BusError;
 	kobject_uevent(&dev->kobj, KOBJ_ADD);
-	if ((error = bus_attach_device(dev)))
-		goto AttachError;
+	bus_attach_device(dev);
 	if (parent)
 		klist_add_tail(&dev->knode_parent, &parent->klist_children);
 
@@ -499,8 +498,6 @@ int device_add(struct device *dev)
  	kfree(class_name);
 	put_device(dev);
 	return error;
- AttachError:
-	bus_remove_device(dev);
  BusError:
 	device_pm_remove(dev);
  PMError:
--- linux-2.6.orig/drivers/base/base.h
+++ linux-2.6/drivers/base/base.h
@@ -16,7 +16,7 @@ extern int cpu_dev_init(void);
 extern int attribute_container_init(void);
 
 extern int bus_add_device(struct device * dev);
-extern int bus_attach_device(struct device * dev);
+extern void bus_attach_device(struct device * dev);
 extern void bus_remove_device(struct device * dev);
 extern struct bus_type *get_bus(struct bus_type * bus);
 extern void put_bus(struct bus_type * bus);
--- linux-2.6.orig/drivers/base/bus.c
+++ linux-2.6/drivers/base/bus.c
@@ -406,21 +406,20 @@ out_put:
  *	- Add device to bus's list of devices.
  *	- Try to attach to driver.
  */
-int bus_attach_device(struct device * dev)
+void bus_attach_device(struct device * dev)
 {
 	struct bus_type *bus = dev->bus;
-	int ret = 0;
+	int ret;
 
 	if (bus) {
 		dev->is_registered = 1;
 		ret = device_attach(dev);
-		if (ret >= 0) {
+		WARN_ON(ret < 0);
+		if (ret >= 0)
 			klist_add_tail(&dev->knode_bus, &bus->klist_devices);
-			ret = 0;
-		} else
+		else
 			dev->is_registered = 0;
 	}
-	return ret;
 }
 
 /**
@@ -593,8 +592,6 @@ static int __must_check bus_rescan_devic
 		ret = device_attach(dev);
 		if (dev->parent)
 			up(&dev->parent->sem);
-		if (ret > 0)
-			ret = 0;
 	}
 	return ret < 0 ? ret : 0;
 }
-
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