[vdr] VDR and Hybrid DVB Cards ( was "HVR 4000 drivers broken - adapter0/frontend1 busy" in linux-media list )

Steffen Barszus steffenbpunkt at googlemail.com
Wed Nov 16 14:00:28 CET 2011


2011/11/16 Manu Abraham <abraham.manu at gmail.com>:
> On Wed, Nov 16, 2011 at 4:38 AM, Klaus Schmidinger
> <Klaus.Schmidinger at tvdr.de> wrote:
>>
>> That is also my understanding of multi frontend devices.
>> If an "adapter" has several "frontends" only one of them can
>> be active at any given time. This has nothing to do with
>> any "explosives" (excuse the pun ;-) and will be implemented
>> in the core VDR code as time permits. Right now I'm cleaning up
>> the "lnb sharing" (aka "device bonding") stuff and will hopefully
>> find more time for VDR development by the end of the year (and
>> thereafter).
>
> If I am following you correctly,
> There is one issue however. If an adapter can have only a single
> frontend, then there will exist another issue:
>
> - Card has dual multi standard frontend(s).
> - Card has CI cards on both the paths (2 CI controllers)
> - Card provides scrambled stream as well as descrambled stream (4
> simultaneous streams)
> - Card needs to swap between the CI modules to take advantage of the
> different modules, rather than reconnecting antenna inputs/manually
> swapping the CI modules.
>
> Eventually, to handle such a situation: all the nodes exposed to the
> application has to be under the "same" adapter, rather than as 4
> different adapters, of which 2 of them won't have any frontend or ca
> devices.

To my understanding the mentioned use case would have - according to
linux-media project logic of how to handle this - would look like

/dev/dvb/adapter0/frontend0
/dev/dvb/adapter0/frontend1
/dev/dvb/adapter0/demux0
...
/dev/dvb/adapter0/ca0
/dev/dvb/adapter1/frontend0
/dev/dvb/adapter1/frontend1
/dev/dvb/adapter1/demux0
...
/dev/dvb/adapter1/ca0

so it would be 2 adapter with 4 frontends. If for some reason they
should be in one adapter how to distinguish between the different
cases ? Maybe i did not understand properly the issue.

Anyhow - if such a case exist - it needs to be discussed how it will
be handled at driver side and how applications need to talk to the
driver - it doesnt help to implement the perfect driver, if nobody can
use it. The multi frontend approach for multi-standard devices as
described here, should logically anyway only be used if more then one
receiption possibility can be connected at the same time. (i.e. if
sattelite cable also can contain the DVB-T signal or both can be
connected same time)

Reading linux-media mailing list doesn't give a clear picture on the
rules on one hand , but on the other hand implementations like the
mentioned one exist. Preferably the API would describe how to handle
it and rules exist for the drivers to be followed, so that
applications dont get broken if following the API.



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