parport: small addition to Documentation/parport-lowlevel.txt

parport: small addition to Documentation/parport-lowlevel.txt

[Kaiwan N Billimoria]

A small note inserted, regarding usage of the parport_unregister_driver 
interface.

Only a single file Documentation/parport-lowlevel.txt is affected 
(pulled from 2.6.18-rc2 :
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;h=8f2302415eff90b0df7aa655f132f9567ff9ccd7;hb=82d6897fefca6206bca7153805b4c5359ce97fc4;f=Documentation/parport-lowlevel.txt
)

Came across this "issue" while writing a parport-based driver.
Does this make sense?

- Kaiwan.

---
--- parport-lowlevel.vanilla    2006-07-21 18:25:24.000000000 +0530
+++ parport-lowlevel    2006-07-21 18:34:52.000000000 +0530
@@ -258,6 +258,18 @@
        ...
 }

+Note-
+If you are using this interface in the "usual" way, you are probably first
+registering your driver with parport_register_driver and unregistering with
+parport_unregister_driver (as shown in the "lp_driver" example about a page
+up from here). You will have attach and detach function callbacks.
+The point is: when your driver is removed from the kernel, your
+cleanup_module function is invoked, which typically invokes
+parport_unregister_driver. This will cause the detach function to kick in.
+Now, this guy should _not_ be (re)invoking parport_unregister_driver, but
+just parport_unregister_device as necessary.
+
+
 SEE ALSO

 parport_register_driver, parport_enumerate