Re: [v4l-dvb-maintainer] [PATCH] v4l2: add hardware frequency seek ioctl interface

[Tobias Lorenz <tobias.lorenz@xxxxxxx>]

Hi,

> Seems fine to me to have an specific ioctl for doing radio frequency seeks.

That seems to be a good approach. Is there any documentation on how the interface is currently implemented?

> It is good to have a patch to a real driver, implementing this feature. I don't
> like the idea of implementing newer ioctls at the API without having an
> in-kernel driver using. Having the driver ioctl implementation helps other
> developers that may need to use this interface on other places.

I would be very happy to add this functionality to my radio-si470x.c driver.
Seek support can be parameterized with this device in many ways.
This is all described in a document from Silabs (available via Google) called AN284Rev0_1.pdf

These parameters are not only used when seeking up/down, but also during frequency tuning.
They are already implemented as module parameters,
as they are country specific and should not be changed during normal operation:
- Band selection (upper/lower frequency limits)
- Spacing selection
- De-emphasis selection

Additionally these parameters are only used by the seek algorithm:
- RSSI Seek Threshold (range: 0..254, 254=highest threshold)
- Signal-Noise-Ratio (range: 0..15, 15=higest SNR ratio)
- FM-Impulse Noise Detection Counter (range: 0..15, 15=best audio quality)

Propably it is wise to give the user space applications the possiblity to change these parameters at run time (ioctl).
Else I'll implement them as module parameters, too.

Bye,
  Toby

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