Reporting signal overload condition for tuners?

Reporting signal overload condition for tuners?

[Devin Heitmueller]

Hi there,

Quick question:  we don't currently have any way to report to userland
that a tuning is failing due to signal overload, right?

There are some tuner chips out there which can detect this condition,
and being able to report it back to userland would make it much easier
to inform the user that he/she needs to stick an attenuator inline.

Has anybody given any thought to this before?  Perhaps use up the last
available bit in fe_status for DVB?

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com

Re: Reporting signal overload condition for tuners?

[Antti Palosaari]

On 07/31/2012 10:56 PM, Devin Heitmueller wrote:
> Quick question:  we don't currently have any way to report to userland
> that a tuning is failing due to signal overload, right?

right

I assume you speak issue where signal is too strong and tuner (or demod 
too?) makes it broken / too noisy for demod.

> There are some tuner chips out there which can detect this condition,
> and being able to report it back to userland would make it much easier
> to inform the user that he/she needs to stick an attenuator inline.

I have never seen such property.

Is that condition something like (RF?) gain control is set minimum but 
signal strength meter is still maximum...

> Has anybody given any thought to this before?  Perhaps use up the last
> available bit in fe_status for DVB?

I left other negative side of LNA integer unused, just thinking it could 
be extended for attenuator. It does not fit for that case, but I have 
seen such feature used by anysee Windows driver. There has been problems 
with strong DVB-C signal in case of TDA10023 demod. I don't know how 
this software attenuator is implemented but I could guess it is done by 
tweaking some tuner or demod property a little bit wrong in order to 
make signal weaker.

And answer for the question is you should likely add new DVBv5 property 
for reading that. I don't like idea of adding such info for frontend status.

regards
Antti

-- 
http://palosaari.fi/