Re: unloading drivers and usage counters

[David Brownell <david-b@pacbell.net>]

> From: David Hinds <dhinds@sonic.net>
> Sent: Sunday, January 21, 2001 10:04 PM
> 
> To decide when to unload a module, the cardmgr daemon keeps track of
> the number of times a module has been requested in response to new
> device insertions; this count can indeed get messed up if people
> manually unload modules, or if cardmgr is killed and restarted.  I am
> not bothered much by this, because the consequences are mostly
> harmless and the user has to go out of their way to mess up the
> automatic usage counting.  In practice, no one has ever complained to
> me about it.

Hmm, so maybe a pure user-mode solution isn't so brittle as that.
That's been in use how many years now?  :-)

This is stuff that could clearly be handled in some /sbin/hotplug
policy code, saving state in some file.


> The PCMCIA subsystem does provide /proc/bus/pccard/drivers, which
> lists what drivers are present, which are modules vs. which are static
> linked, and the actual number of present devices that are associated
> with each driver.  Cardmgr currently only uses the module/static flag
> from this file, so that it won't bother trying to remove a static
> driver; it would not be much work to also use the usage information
> for precise decisions about when to unload modules.

Sounds like this is something that the "linux hotplug" system should
perhaps consider providing in a more general way, for all levels of
the driver stacks.

- Dave



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