Messages in this thread |  | | | Date | Fri, 5 Aug 2011 13:47:28 -0400 | | From | "Emilio G. Cota" <> | | Subject | Re: [PATCH 5/8] staging: vme: add functions for bridge module refcounting |
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On Fri, Aug 05, 2011 at 10:24:55 +0100, Martyn Welch wrote: > 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.
But the granularity is wrong; if you want to know whether the bridge is being used, just keep track of the devices *which want to make known* that they're under the bridge.
> 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.
A driver leaking a resource will then leave a bogus refcount on the bus driver--a clear case of self-inflicted pain.
The argument of "poorly written drivers" does not apply; I would expect all the merged drivers to be "good quality" only, that's why we want to be upstream and why we put effort in reviewing. Your point is well-intentioned, but in practice we'd be shooting ourselves in the foot, potentially ending up with an unremovable vme bridge module--which is worse than a driver leaking a resource.
Refcounting must be kept simple & stupid; doing it behind the backs of the drivers we're trying to protect is a mistake.
Emilio
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