On Fri, Aug 12, 2011 at 12:30:49 +0200, Manohar Vanga wrote:
> This patch adds functions that allow for reference counting
> bridge modules. The patch introduces the functions
> 'vme_bridge_get()' and 'vme_bridge_put()'.
>
> The functions are automatically called during .probe and .remove
> for drivers.
(snip)
> @@ -52,6 +52,48 @@ static struct vme_bridge *dev_to_bridge(struct device *dev)
(snip)
> +int vme_bridge_get(unsigned int bus_id)
If it isn't exported, it should be declared as static.
> +{
> + int ret = -1;
hmm perhaps -ENXIO here would be better, since the outcome
of this function is either that or success.
> + struct vme_bridge *bridge;
> +
> + mutex_lock(&vme_buses_lock);
> + list_for_each_entry(bridge, &vme_bus_list, bus_list) {
> + if (bridge->num == bus_id) {
> + if (!bridge->owner)
> + dev_warn(bridge->parent,
> + "bridge->owner not set\n");
Don't do this; it will throw a false warning if the kernel is
built without module support. Note that in that case
THIS_MODULE == (struct module *)0.
try_module_get() and module_put() do the right thing for all
possible configs. Trust them.
> + else if (try_module_get(bridge->owner))
> + ret = 0;
> + break;
> +void vme_bridge_put(struct vme_bridge *bridge)
should be static as well
> +{
> + if (!bridge->owner)
> + dev_warn(bridge->parent, "bridge->owner not set\n");
> + else
> + module_put(bridge->owner);
ditto, remove the warning.
> +
> +/*
> * Find the bridge that the resource is associated with.
> */
> static struct vme_bridge *find_bridge(struct vme_resource *resource)
> @@ -1496,14 +1538,20 @@ static int vme_bus_probe(struct device *dev)
> {
> struct vme_bridge *bridge;
> struct vme_driver *driver;
> - int retval = -ENODEV;
> + int retval = 0;
>
> driver = dev_to_vme_driver(dev);
> bridge = dev_to_bridge(dev);
>
> + if (vme_bridge_get(bridge->num))
> + return -ENXIO;
> +
> if (driver->probe != NULL)
> retval = driver->probe(dev, bridge->num, vme_calc_slot(dev));
>
> + if (driver->probe && retval)
> + vme_bridge_put(bridge);
If the driver doesn't provide a .probe, we would still increment
the refcount of the bridge module. Is that reasonable? I dunno.
If there's no .probe then the device is doing something
weird, and probably either it doesn't have much to do with a
particular bridge (i.e. it manages no "real" devices) or
it'd need to manage its own resources (in which case we could
easily export vme_bridge_get/put.)
Perhaps then the following would be more appropriate,
what do you think?
+ if (driver->probe) {
+ if (vme_bridge_get(bridge->num))
+ return -ENXIO; /* although this could change, see above
comment */
+
retval = driver->probe(dev, bridge->num, vme_calc_slot(dev));
+ if (retval)
+ vme_bridge_put(bridge);
+ }
+
return retval;
.. and then remember to do
+ if (probe)
+ vme_bridge_put(bridge)
in vme_bus_remove(), which in your patch is unconditional (correctly
matching the unconditional get() in vme_bus_probe)
> @@ -1519,6 +1567,8 @@ static int vme_bus_remove(struct device *dev)
> if (driver->remove != NULL)
> retval = driver->remove(dev, bridge->num, vme_calc_slot(dev));
>
> + vme_bridge_put(bridge);
> +
> return retval;
> }
> diff --git a/drivers/staging/vme/vme.h b/drivers/staging/vme/vme.h
> index 4155d8c..eb00a5e 100644
> --- a/drivers/staging/vme/vme.h
> +++ b/drivers/staging/vme/vme.h
> @@ -165,6 +165,5 @@ int vme_slot_get(struct device *);
> int vme_register_driver(struct vme_driver *);
> void vme_unregister_driver(struct vme_driver *);
>
> -
> #endif /* _VME_H_ */
I'm certainly no checkpatch taliban, but guess you probably
didn't want to send this line change.
Cheers
Emilio
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