Re: Adding PCMCIA support to the kernel tree -- developers needed.

[Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de>]

> Module startup automatically calls init then register.  Conditional
> shutdown checks for zero use count, calls unregister then flushes any
> other cpus that had just entered the module.  If the flush was

Flushing ? How ?

> successful, call exit.  If the flush was unsuccessful (somebody just
> started using the module), call register to make the services available
> again.

Doing so means that there's a time where the device is unregistered
illegitimately. Wouldn't it be simpler to take the big kernel lock for the 
check ? The unregistering would have to take it anyway.

> There is also an unconditional shutdown mode.  Call unregister and even
> if the module is still in use, do not call register again.  When the
> use count finally goes to zero, the exit routine is called and the
> module is removed.

This is definitely needed, but why two calls for that ? It would be easier to
provide a callback to be called when the use count reaches zero.

> I think this will help hot unplugging.  When the device disappears, the
> driver internally marks its hardware as unusable and schedules an
> unconditional shutdown of itself, all out of the interrupt handler.

Is that really necessary ? Can't a kernel thread be used ? It is much easier
than coding in interrupt.

> Unconditional shutdown calls unregister which stops any new code
> entering the module.  The driver returns -EIO for all outstanding
> requests which will eventually result in the outstanding users calling
> close() or its equivalent and leaving the module.  When the use count
> finally goes to zero, exit releases the resources and the module is
> removed.  For built in code we do almost the same, the only difference
> is that built in code is not removed from memory.

That is wise.

	Regards
		Oliver

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