[linux-dvb] Re: DVB-CI question

[Peter Urbanec <linuxtv.org.dvb@urbanec.net>]

Andrew de Quincey wrote:

> On Friday 26 March 2004 14:33, Klaus Schmidinger wrote:
>  
> > If it's not hard to do in userspace, why is it so hard in the driver?
> > Why should every application implement this by itself? I'd say this should
> > be done by the driver, and the applications shall exchange complete TPDU's
> > with the driver.
> >    
> IMO, the driver should be as simple as possible. I don't think the CAM 
> interface benefits speed-wise from the reassembly being in the driver, so, 
> apart from saving a little bit of extra code in userspace I can't see any 
> good reason for the reassembly being in the kernel. Each app already has to 
> implement all the other layers of the EN50221 control protocol stack itself; 
> why not this extra bit as well? 
>  
If I can chime in with a purely design based rationale...

Why only think of this from the point of driver vs. application? I agree 
with Andrew that the driver should be as simple as possible. The less 
code one has to run in the kernel context the better. However, I don't 
particularly like the idea of each application having to reimplement the 
same basic code - someone  is likely to get it wrong.

How about adding another layer? Take all this from the driver, but 
provide a library implementation that applications can dynamically link 
to to get the reassembly for free. That way you get the benefit of both 
worlds. You keep the driver simple and the application developer doesn't 
have to reinvent the wheel.

Any reason why that something like that would not fly?

--
   "Beauty lies in the hands of the beer holder."




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