On Thu, 4 Jul 2002, Arnd Bergmann wrote:
> On Wednesday 03 July 2002 18:46, Patrick Mochel wrote:
>
> > However, in any class, there may be multiple interfaces available for a
> > particular device. It's these interfaces that userspace sees. A driver may
> > implement some or all of those interfaces, and they may or may not be
> > present based on the configuration of the kernel.
>
> Ah, that's the missing bit, at least the tape driver is no problem then. There
> is still a slightly different case that I'm not sure about. In the case of
> CTC, the type of a device is determined during probe (depending on what's on
> the other side, but the driver handles both tty and network ctc devices. It
> seems logical if this type maps to a device class, not an interface, as there
> is no network device that ever implements a tty interface or vice versa (in
> ppp, you have a parent-child relationship between these, not identity).
> I suppose then, the ctc module should actually implement two drivers, one
> for each class and handle detection in the two probe methods, right?
Yes, exactly.
> A similar example is the 'lcs' network driver, whose devices can be either
> ethernet, token ring or fddi NICs. You said that these would be subclasses
> of the network class, but could lcs also be simply belong to a non-specific
> network driver class and not put each device in the respective sub class?
> Or would it make more sense to have special subclass just for network
> drivers with more than one layer-2 protocol?
Thinking about it some more, I'm wondering if we treat them only as
belonging to the top-level networking class and have the layer-2 protocols
be interfaces to those devices. For most devices, there would be only one
interface, but it would also cover the case in which a device supports
multiple prototcols.
This is similar to the input layer. Initially, I had grouped specific
devices into subclasses. But, I learned that a device really belongs to
multiple subclasses (e.g. evdev and mouse). Hence the concept of one class
with multiple interfaces...
-pat
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