[linux-dvb] Re: Problems with TechnoTrend dec2000-t USB

[Holger Waechtler <holger@convergence.de>]

Felix Domke wrote:
> I for myself would like to have the lower dvb driver layer being able to 
> handle calls from interrupt context. tasklets always involve a higher 
> latency, and sometimes (like in our case) it's difficult to buffer the 
> data away. Or is there a strong reason not to support this? (No, it's 
> not because my lazyness, but on slow platforms like the dbox2, it helped 
> a lot to move the queue-handler from a tasklet directly into the 
> interrupt handler in terms of speed. I think it was changed to a 
> bottom-half handler now, which seems to be faster (=lower latency) than 
> a tasklet (why??))
well, after thinking twice I remind that they suggested in the Linux 
Device Driver book (Alessandro et al) to copy the data out of the queues 
in the irq handler in case for short buffers and do all the protocol 
handling stuff later.

Well, this introduces an additional copy step for each packet, but it 
sounds as if this is a good compromise which works well in network drivers.

Holger



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