[PATCH] Re: [linux-dvb] [PATCH] Multi protocol support (stage #1)

Manu Abraham abraham.manu at gmail.com
Mon May 15 10:08:13 CEST 2006

Trent Piepho wrote:
> On Sun, 14 May 2006, Manu Abraham wrote:
>> Trent Piepho wrote:
>>> Can you show me, with code, what I would do to check if an ATSC tuner
>>> supports QAM-256?  I posted code to do this as an example for older versions,
>>> it should only be a couple lines.
>> at the application side,
> I'm sorry, but I still do not understand how to do this simple task with this
> new API.  It seemed clear to me with version 3, but now I'm at a loss.  Can
> you please answer these couple of questions?

Sure, i am obliged to do so.

> 1.  DVBFE_GET_DELSYS returns:
>     a) The CURRENT active delivery system
>     b) A bitset of SUPPORTED delivery systems


This can be done
(1) query back from h/w registers
(2) if hardware does not support querying back, cache a copy of the 
modulation in the device state ADT, that was last set.

Both supported at driver level.

> 2.  DVBFE_GET_INFO, in the delivery field, returns:
>     a) The CURRENT active delivery system
>     b) A bitset of SUPPORTED delivery systems


Info is static information as usual, the old style.

> 3.  DVBFE_GET_PARAMS returns:
>     a) The CURRENT settings of the front-end, e.g. the modulation of the
>        current channel tuned to, the current FEC rate, and so on.
>     b) The SUPPORTED modulations, fec rates, and so on.

a) The cached values/from the hardware registers.

> 4.  With this new API it is possible to:
>     a) Query the ABILITIES of the front-end.  For example, find out if
>        the front-end supports ATSC, and if so, if it supports 256-QAM.
>     b) Find the current settings of what the front-end is tuned to.  For
>        example, determine if the current channel is 64-QAM or 256-QAM.
>     c) Both a and b

a) can be done by the driver
b) depends if the hardware supports querying back the modulation in some 
way. If hardware doesn't support, you can make it to do so by caching 
the values in the device state struct.

> I have made the questions multiple choice, so it will be less trouble for
> you to answer them.

I will update the stb0899 driver regarding the changes, probably might 
be helpful as an example.


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