[linux-dvb] [RFC] add "read_signal_strength" function to dvb_tuner_ops

Michael Krufky mkrufky at linuxtv.org
Fri Aug 31 16:30:30 CEST 2007

Henk wrote:
> Of course from a kernel perspective it is a simple addition, but where
> should we form a userspace perspective decide on which signal strength
> function to use?
> I don't think an extra interface should be needed here.

This is an addition to the *internal* API -- This means no change to 
> For example if a demodulator is unable to provide signal strengths on
> his own there is always the possibility to request it from the tuner
> (if available) and report that.
That's the point -- the addition of this function to dvb_tuner_ops will 
expose this functionality of the tuner driver to the demod driver.
> For example how about this alternative. In the demod driver you could use:
> int  demod_get_rf_strength(struct dvb_frontend *fe, u16 *strength)
> {
>    /* No I dont support this so see if we can get something from the tuner */
>    if ( fe->ops.tuner_ops.get_rf_strength(fe, strength) )
>           return fe->ops.tuner_ops.get_rf_strength(fe, strength);
>    return -ENOSYS;
> }
This is exactly what I was describing...  The entire point, however, is 
that there is no tuner_ops.get_rf_strength as of yet.  I was proposing 
to add this new function pointer to struct dvb_tuner_ops, an internal 
structure only available *within* the kernel..
> That way you can decide in the demod driver what's the best way on how
> to deal with this specific hardware "feature".

Thank you for agreeing with me ;-)

Henk wrote:
> Sorry,
> My mistake, I was under the impression that "read_rf_strength" was
> already a tuner interface.
> So in that case it would be usefull to have included in the tuner interface.
> Still policy on whether it is reported to userspace should reside
> within the demod driver as outlined below I think.
> As for the name I think it would cause less confusion to call it
> similar to the function thats used in "struct frontend"
> (get_signal_strength).

Manu and I together decided against that.  get_rf_strength is more 
appropriate, since he plans to add similar functions later on for 
reading IF strength amongst other values.

Thank you for your comments.



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