[linux-dvb] Re: CVS UNLOCKED

[Michael Hunold <hunold@linuxtv.org>]

Hi,

On 10/28/04 19:49, Holger Waechtler schrieb:
> I'd like to use this code as testbed fo v5 experiments, thus we bypassed 
> the dvb_frontend infrastructure: the direct dvbdev access allows a 
> trivial mmap() implementation as discussed some days ago in with John 
> Dalgiesh. 
Just a side note: v4 contains a mmap() implementation for both recording 
filters as well as memory inputs that goes through the dvb-core. I admit 
that the implemenation is more useful for hardware with special 
capabilities and not for budget cards.

Again it's the question how much software emulation you want to put on 
top of the budget drivers (for example emulate section filters in 
software). We should keep in mind that DVB software should run on both 
STBs and normal PCs. Perhaps this can be achieved by using an alsa-like 
userspace library for budget cards, that does nothing for hardware with 
special capabilities.

> I'd like to try to go even one step further and mmap both the 
> TS ringbuffer and a special memory page containing the current DMA 
> pointer, frontend status parameters and the DMA buffer partitioning 
> table to userspace. If this works and makes sense it may simplify the 
> API while allowing trivial-to-implement v3 backward compability.
Hopefully all existing budget cards will support that interface. It 
would be a pity if there is some hardware design limitation (for example 
broken or ill dma capabilties) that prevents it from using your proposal.

> Holger
CU
Michael.