definition of terms (was: Re: Adding PCMCIA support to the kernel tree -- developers needed.)

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

> > I fear we are being sucked down by semantics.
>
> You can't get away from that in design discussions.  Gotta
> eliminate confusions up front.
>
> And this application structure is very important.  You can't
> design a "system" without knowing the ways people interact
> with it ... /dev/NNN is no more than one part of a 1970s
> solution to a simpler system problem than we have today.
> We can still use it, but it's not a straightjacket to live in.

OK. Let me list all terms used up to now and give a preliminary definition.


'physical device' - hardware, in this context usually hotpluggable

'hotplug event' - any event relating to a hotpluggable device which the 
kernel may report to user space

'user space agent' - task the kernel spawns in reaction to a hotplug event

'interface driver' - a kernel space driver that user space can use to talk to 
a physical devices. There may be more than one interface driver per physical 
device, or in rare cases, none.

'logical driver' - interface the user space agent may set up, which allows 
the rest of user space to use the services a physical device offers, optional

'device name'  - a name userspace uses to identify the interface driver

'stable name' - a device name that depends on a unique characteristic of a 
device or on the way a device is connected to a bus

'physical location' - a description of how a device is connected to a bus.
at one time a connected physical device has one physical location and there 
is a maximum of one device to a physical location

Now to an example:

physical device: a USB scanner

hotplug event: scanner is plugged in + possibly others (to be decided)

user space agent: /sbin/hotplug + scripts called by it

interface driver: usbscanner.o

logical driver: epson backend of SANE

I introduced the term 'interface driver' because it is needed.

	HTH
		Oliver

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