Re: [PATCH 5/8] staging: vme: add functions for bridge modulerefcounting

From: Manohar Vanga
Date: Tue Aug 09 2011 - 09:27:24 EST

Hey Martyn,

> I think that by refcounting the resources being used we will know whether a
> bridge module is being used or not, thus whether it can be unloaded or not. By
> reference counting the use of resources we minimise the chance of poorly
> written drivers using resources, but not registering the fact that they are in
> fact using a VME bridge.

In the end, this discussion is about what we want the bride module reference count
to represent. I see your point here that it would be really useful to know what
resources have been allocated. I am just wondering whether the module refcount is
a good place to give information on allocated resources (rather than the bridge
module refcount).

I am not really an expert in these matters but would something like a sysfs file
be a cleaner approach to providing information on allocated resources within the

With this approach, I am also thinking about cases where resources are not allocated
within the probe call. This can cause issues if the bridge module is removed after
a successful probe but before the resources are allocated. This would be a direct
bug :-/

If we really don't want explicit module refcounting by drivers, can we perhaps use
the return value of the probe to automatically do this? eg. in vme_bus_probe() like

int ret = 0;
if (driver->probe)
ret = driver->probe(vdev);
if (ret)
return ret;

Just a thought. Feel free to shoot it down if you think it's the incorrect
approach :P


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