Unloading drivers, start-up, shut-down and some clean-ups

[Stamatis Mitrofanis <ewstam@softhome.net>]

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  Hello everybody. I have the 2001_04_24 release of the hotplug scripts. 
I figured it would be good to be able to automatically unload drivers 
too so I did some work on the subject. Unfortunately, it _wasn't_ as 
simple as implementing the "remove" event in the policy agents and so 
that makes it a _lot_ of work on the subject. :-)

For properly unloading drivers there need to be some changes in the way 
the boot scripts, the agent scripts and the driver-specific 
scripts (well, that doesn't leave much else :-)) are organized. Here's what:

My idea is to put the functonality of the ".rc" boot scripts in the 
".agent" scripts and have a central subsystem which triggers all others 
(via devices of it) at startup and shutdown -- creating a hierarchy this 
way. This means adding "start" and "stop" events and getting rid of 
"/etc/hotplug/*.rc" scripts. An example is that a PCI device (the host 
controller) is what "enables" the USB subsystem (or a part of it in the 
case of multiple controlers). So it goes for all other cases as long as 
the hotplug scripts are dealing only with hardware devices. This way the 
subsystems will be "started" and "stopped" in an order which is more 
appropriate than the current lexical order.

My suggestion is also to have driver-specific "*.agent" (instead of just 
"*" scripts:-)) scripts which will be called _in place_ of  (and not in 
addition to) modprobe (of course, they will call modprobe themselves if 
necessary).
- This makes it possible for scripts to do their stuff before and/or 
after "modprobe"ing.
- It also eliminates the need for a blacklist (you (or a package) can 
simply add empty agents)
- It completes the previous hierarchical design which I was talking 
about. "uhci.agent" for example can "start" the USB subsystem when "added" .
- The driver-specific *.agent files can be enumerated very simply (with 
this glob).
- The driver-specific policy agents can have their own homes and invite 
friends and relatives as well... :-) I mean that each driver-specific 
agent can have its own driver-specific subdirectory (just like each 
subsystem-specific agent can have its own subsystem-specific subdirectory).
- Aside the previous, each driver (and this is the most useful part) can 
have its own .usbmap (or .pcimap or similar) in the subsystem-specific 
directory. This *.usbmap (as an example) file should be parsed as well 
by usbmodules. This makes usb.handmap, usb.usermap and similar files 
unnecessary.

Another thing is that the individual policy agents should be separated 
from each other (/etc/hotplug/hotplug.functions is ugly :-)) and thus 
should have very few common parts. That's because future hotplug agents 
might not be only (or at all) for (un)loading kernel modules for 
hardware devices and they just can't ignore any common functions (like 
driver-loading functions or so) that are given to them. Now, that may 
sound bad since it means duplicating a couple of lines of script but I'm 
playing safe :-)...
Here's a file layout:
- Anything matching /etc/hotplug* is hotplug specific
- Anything matching /etc/hotplug/xxx* is xxx-subsystem-specific.
- Anything matching /etc/hotplug/xxx/yyy* is yyy-driver-specific.
Here's a uniform naming scheme:
- If * corresponds to nothing then it's a directory.
- If * corresponds to ".agent" then it's a script that processes hotplug 
requests.
- If * corresponds to ".conf" then it's sourced from the corresponding 
.agent script and related ones.

So, my suggestion is also to create subsystem-specific .conf files (as 
well as a global one) that will be sourced from agent scripts and will 
define relevant variables and functions. The global /etc/hotplug.conf 
file will define the "msg" function ("mesg" is already used as a program 
name!!!) and a variable for the "central" subsystem (normally pci). It 
will also be sourced from /etc/init.d/hotplug .

I must admit now that my fingers are getting tired... :-) I hope I 
covered everything I changed. All this work I did was mostly a rewrite 
and a clean-up of the scripts. Of course, I have attached a patch for 
the 2001_04_24 release. I have tested my changes on two machines with 
two USB devices and it seems to load/unload everything fine ("works for 
me") like the drivers for sound cards, UHCIs etc. . Yet it needs a few 
FIXMEs fixed to be 100% .

Furthermore, I hope I did something positive here so please, anyone, do 
what you will to help.

All yours(!),
Stamatis


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