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SubjectRe: [Q]: Linux and real device drivers
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>>>>> "Bret" == Bret Indrelee <breti@bit3.com> writes:

>> > I don't say they have to be shipped seperately, but if they are
>> separated, > they can be handled like normal high-priority tasks,
>> swapped out if
>>
>> They can't because they need to handle interrupts and get high
>> performance

Bret> Actually, drivers should be structured as high priority tasks,
Bret> at least from the scheduling point of view. The interrupt
Bret> handler itself should only do enough to stop the card from
Bret> interrupting and then pass control to a software handler.

It certainly shouldn't, thats going to cause horrible device service
latency for high performance devices.

Bret> Tied to the kernel is a lot different than requiring a recompile
Bret> for every kernel patch. It is possible (as in most manufacturers
Bret> do it) to have a kernel interface to handle the normal functions
Bret> required of a device driver.

And these may change if there is good reason for doing so. The Linux
kernel does not guarantee a fixed set-in-stone driver API.

Bret> Putting in a patch on Solaris doesn't require that you then go
Bret> out and recompile every device driver on the system. Same goes
Bret> for HP-UX or AIX.

Well these systems have the problem that they have to keep third party
vendors happy. We don't since most of our code is included in the
public source, and the people who wants to do binary-only drivers will
have to live with that.

Bret> That doesn't mean that there is no reason to provide an opaque
Bret> and stable interface between the device driver and the operating
Bret> system.

Sure there is, it is not worth the effort. There have been cases in
the past where the driver API had to change and there will be cases in
the future.

Jes

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