[linux-dvb] Re: DVB-CI question

[Andrew de Quincey <adq_dvb@lidskialf.net>]

On Friday 26 March 2004 17:53, Johannes Stezenbach wrote:
> Andrew de Quincey wrote:
> > Its the complex list handling for fragment reassembly thats the bit I
> > don't see any reason for having cluttering up the kernel. Theres no high
> > bandwidth data being transferred, so theres no real gain in doing in the
> > kernel. However, in the av7110 instance, I can see that perhaps there
> > were other reasons it was done in the firmware, but those are not
> > necessarily the case here.
> >
> > The extra locking in mine is because it is intended to be a generic API
> > implementation for CA devices, along the lines of the other parts of
> > dvb_core, so I cannot make any assumptions about any particular device.
> > Note that the implementation is pefectly happy with dealing with the
> > av7110-style defragmented packets as well, so it could be used to replace
> > the current av7110 opensource CA code with the generic API
> > implementation.
> >
> > I can write sample userspace code for doing the defragmentation if that
> > would help people (I've already released a partial version of it, so I
> > can release that fine).
>
> Well, I would like to avoid changing the (semantics of the) CI API .
>
> Anyway, if you make your code available we can then discuss if
> your proposed changes are after all a good thing.
>
> I'd like to hear Ralph's or Marcus's opinion, as they originally
> wrote the CI code in the av7110 firmware and driver, and I think
> they know a good deal more about that stuff than I do.

Actually, come to think of it, what about the following:

Now that I've stripped the extra complex code from the library, I could add a 
simple de-fragmenter to the read()/write() interface for back compatability. 
It doesn't need to be blindingly fast.

However, I have some proposals for fixing the IOCTL interface, to support 
different types of CA device properly, and removing some the cruft. I suggest 
we then just have different device types for the CA_GET_MSG/CA_SEND_MSG 
ioctls, which would work quite nicely with the other changes I had in mind.

Note the changes only affect the CA_GET_MSG/CA_SEND_MSG ioctls, and nothing 
uses them right now 'cos they're a bit broken.....


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