[linux-dvb] Re: [RFC][ANNOUNCE] blindscan: auto searcheverything

[Roberto Ragusa <mail@robertoragusa.it>]

On Tue, 3 Aug 2004 20:12:36 +0200
Johannes Stezenbach <js@convergence.de> wrote:

> Roberto Ragusa wrote:
> > 
> > OK, so I propose this:
> > 
> > - you use FE_SET_FRONTEND as usual
> > - then, you call FE_SET_AUTO_SEARCH passing something as
> > 
> > struct dvb_autosearch {
> > 	fe_autosearch_t	parameter;
> > 	__u32		lower limit;
> > 	__u32		higher limit;
> > }
> > 
> > typedef enum fe_autosearch_t {
> > 	FE_AUTO_SYMBOL_RATE
> > }
> > 
> > - then you use FE_GET_FRONTEND to read the sr
> 
> If I understand it correctly, all parameters passed
> to FE_SET_FRONTEND would be set to AUTO, except for the
> frequency? If so, then it would make more sense to me
> to add the frequency to struct dvb_autosearch, and not
> use FE_SET_FRONTEND for scanning.

All parameters could be set to AUTO, but I may want to
force INVERSION_OFF and/or FEC_7_8.
As this function will be used to catch feeds, we shouldn't
impose arfificial limitations to the hw capabilities.

> This also needs to avoid the zigzag scan which FE_SET_FRONTEND
> normally does.

BTW, mt312 has max_drift=0 because the hw can autocompensate
small frequency errors.

> (BTW, typedefs are deprecated for kernel code (only allowed
> for explicitly opaque data types)).

Until now, I've been contested:

1) "&buf" instead of "buf"
2) "//" comments
3) use of typedef

the funny part is that

1) I copied&pasted existing code
2) "//" comments are everywhere
3) typedef are everywhere in frontend.h

:-) :-) :-)


> > He proposed many ioctl (START_SCAN, CONTINUE_SCAN, STOP_SCAN),
> > and they may be useful in the future even if they are not needed
> > at the moment.
> 
> These are only useful if the hardware can indeed scan a frequency
> range automatically. If not, they are useless as userspace can
> only check (a small band around) one frequency, and retrieve the
> result (no signal, or a full parameter set). So please check
> the data sheets again (for mt352 and mt312) to see if this is
> true.

mt312: it is possible to specify  a small band (+-15MHz max,
+-6MHz default); so not a frequency scan, just autofinetuning.

Where are we?
I'd say, a struct with min_sr and max_sr and a new ioctl to
be called after normal tuning is enough for mt312.

Regards.
-- 
   Roberto Ragusa    mail at robertoragusa.it