[linux-dvb] [patch] Add support for different tuning algorithms

Johannes Stezenbach js at linuxtv.org
Tue Nov 15 21:08:16 CET 2005

On Tue, Nov 15, 2005 Felix Domke wrote:
> Some frontends support blindscanning, but require heavy software support
> for this (Fujitsu mb86a15 for example). Such code is not really suitable
> in the kernel (it sleeps, includes complicated algorithms etc.), so i
> think the best would be to make it a userspace library with frontend
> specific private ioctls, providing more or less direct register (or even
> i2c) access. What do you think?
> Blindscanning on DVB-T would require the same - most demods can do this
> way better than any generic API could handle.

I would prefer if we could find a generic scanning API.

Doesn't it work that way:

- program PLL for frequency to scan
- program demod for scanning
- poll some demod register until it signals completion
  (or use irq if available)
- pass result to userspace (e.g. event, wake up poll(2), ioctl)
- get frequency step for reprogramming PLL from driver
- repeat

I know the driver software from the fe vendors often uses
floating point and makes it look complicated, but IMHO
it doesn't have to.


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