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SubjectRe: Patch: linux-2.5.58/drivers/base/bus.c ignored pre-existing devices

> device_attach() in linux-2.5.5[78]/drivers/base/bus.c has a
> bug. Any device that is detected before its driver is loaded is
> forgotten.

> Anyhow, getting back to business, the problem arose due to a
> botched change in drivers/base/bus.c that apprently was intended to
> allow a driver->probe function to return an error other than -ENODEV
> and thereby cause the whole binding process to abort. At least that's
> what I think the extra code was inteded to do. If not, I could shrink
> the code by making device_attach return void.

The extra code was an attempt at properly handling failure of ->probe(),
and to make sure that an error from ->probe() (e.g. -ENOMEM) is propogated
up.

The cause of the problem you're seeing is that if a device wasn't bound to
a driver, -ENODEV was returned, causing it to be removed from the bus's
list of devices.

To remedy this, I've changed the semantics of bus_match() to return the
following:

* 1 if device was bound to a driver.
* 0 if it wasn't
* <0 if drv->probe() returned an error.

This allows the caller to know if binding happened, as well as bubble the
error up.

Greg notified me of this yesterday, and I sent him the following patch. I
haven't pushed it upward yet, since he hasn't had a chance to test it. If
you get a chance, please try it and let me know if fixes your problem..

Thanks,

-pat

===== drivers/base/bus.c 1.38 vs edited =====
--- 1.38/drivers/base/bus.c Mon Jan 13 10:34:12 2003
+++ edited/drivers/base/bus.c Tue Jan 14 16:41:22 2003
@@ -256,22 +256,27 @@
*
* If we find a match, we call @drv->probe(@dev) if it exists, and
* call attach() above.
+ *
+ * If the deivce is bound to the driver, we return 1. If the bus
+ * reports that they do not match (bus->match() returns FALSE), we
+ * return 0. Otherwise, we return the error that drv->probe()
+ * returns.
*/
static int bus_match(struct device * dev, struct device_driver * drv)
{
- int error = -ENODEV;
+ int ret = 0;
if (dev->bus->match(dev,drv)) {
dev->driver = drv;
if (drv->probe) {
- if ((error = drv->probe(dev))) {
+ if ((ret = drv->probe(dev))) {
dev->driver = NULL;
- return error;
+ return ret;
}
}
device_bind_driver(dev);
- error = 0;
+ ret = 1;
}
- return error;
+ return ret;
}


@@ -298,8 +303,11 @@

list_for_each(entry,&bus->drivers.list) {
struct device_driver * drv = to_drv(entry);
- if (!(error = bus_match(dev,drv)))
+ if ((error = bus_match(dev,drv))) {
+ if (error > 1)
+ error = 0;
break;
+ }
}
return error;
}
@@ -322,6 +330,7 @@
{
struct bus_type * bus = drv->bus;
struct list_head * entry;
+ int error = 0;

if (!bus->match)
return 0;
@@ -329,8 +338,12 @@
list_for_each(entry,&bus->devices.list) {
struct device * dev = container_of(entry,struct device,bus_list);
if (!dev->driver) {
- if (!bus_match(dev,drv) && dev->driver)
- devclass_add_device(dev);
+ if ((error = bus_match(dev,drv))) {
+ if (error > 0)
+ error = devclass_add_device(dev);
+ else
+ break;
+ }
}
}
return 0;
@@ -396,7 +409,8 @@
if ((error = device_attach(dev)))
list_del_init(&dev->bus_list);
up_write(&dev->bus->subsys.rwsem);
- sysfs_create_link(&bus->devices.kobj,&dev->kobj,dev->bus_id);
+ if (!error)
+ sysfs_create_link(&bus->devices.kobj,&dev->kobj,dev->bus_id);
}
return error;
}
-
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