[linux-dvb] Multiple fronends on a single shared ransport bus

Christophe Thommeret hftom at free.fr
Wed Oct 4 18:31:50 CEST 2006


Le Mercredi 04 Octobre 2006 18:08, Steven Toth a écrit :
> Hi,
>
> The WinTV-HVR3000 has a single transport bus on the cx2388x shared
> between a cx22702 DVB-T and a cx24123 DVB-S. The windows driver manages
> the hardware to ensure an application can stream from one or the other
> demod.
>
> In terms of Linux and the current tree, it's a trivial thing to add
> basic DVB-T only support, or it's a trivial thing to add DVB-S only
> support - mainly because both of these demod/tuners are already
> supported in the tree. Adding dynamic switching between either demod is
> an interesting problem.
>
> On one hand with solution #1 we have the multiproto tree which tries to
> address some of these issues (at the frontend ops only, with no
> considerations to the implementation within the frameworks).
>
> On the other hand with solution #2 (for current support modulation
> schemes) why don't we simply register multiple frontends during
> dvb_register?
>
> I created a cx88 patch last night to try this and the only questionable
> result is that you end up with a solution like this:
>
> /dev/dvb/adapter0/fe0   .. cx24123 DVB-S on a HVR3000
> /dev/dvb/adapter1/fe0   .. cx22702 DVB-T on the same HVR3000
> /dev/dvb/adapter2/fe0   .. dvico ATSC LG demod I also had installed.
>
> The simple thing about a solution like this is that:
> a. a/t/szap -a <fenum> worked with zero changes.
> b. The recent cx88 bus arbitration patches ensured that only one of
> adapter0/fe0 or adapter1/fe could be opened at any one time. (As expected).
>
> I don't see solution #2 as a replacement for solution #1, but the
> patches are pretty trivial and localised within a single framework.
>
> A few consideration:
>
> How will new or existing applications deal with solution#2?
> Do any existing drivers deliver adapter0/fe0 and adapter0/fe1 and which
> applications support that?

 At least, Kaffeine should work with frontend1/dvr1/demux1 (in fact, i've 
always assumed that a multi tuner adapter would provide multiple 
frontends/dvr/demux)


-- 
Christophe Thommeret



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