Re: libusb1.0 API

> So one extra abstraction layer which is a superset of all supported
> OS USB APIs. Can that be created easily enough?
> 
see my previous mail on libusb_*_submit() example

> 
>>> Does there have to be any corner cases left? :)
>> There will always be races (eg. the device disappears during a
>> transfer from the device to the host. do we return the data
>> transferred so far or just tell the caller the request failed
>> because the device went away).
> 
> Both, USB is hot-pluggable. More?
> 
well, this needs to be documented so we don't surprise the libusb 
application writer and make it easy for writing a backend.

When I wrote the solaris implementation of libusb.0.1.0.8 I had to use 
the linux implementation to figure out how to do the implementation and 
handle corner cases. Ideally, a back-end writer should be able to work 
from a "spec" or a set of man pages.

> 
>>> This is obviously the purpose of libusb. Please expand on your
>>> thoughts about the frontend/backend split. I don't know if I like
>>> it.
>> see above, I hope you like it
> 
> Still not sure. I think I would prefer shared functions for common
> tasks. The problem I see is that a change in one OS USB API will
> affect other OS ports because the internal API (front/back split)
> has to change.
> 
there is that possibility. The interface between front-end and back-end 
needs to be carefully designed.

> 
>> By having most of the implementation in the front-end, we will get
>> for "free" that each OS implementation behave very similar in many
>> respects.
> 
> Until one doesn't.
> 
> 
Hopefully the front-end can at least ensure that error codes are consistent

>> the idea of the test device is that it really behaves very poorly
>> and unpredictably. It should never crash libusb or the kernel and
>> it should in theory provide complete code coverage during the
>> testing
> 
> This is quickly turning into a separate project much bigger than
> libusb. :) It's also a good test for different kernels.
> 
yeah, I always wanted to have that kind of device for our USB driver 
testing 

cheers

fritS

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