[linux-dvb] Revisiting the SNR/Strength issue

Andreas Oberritter obi at linuxtv.org
Fri Oct 17 11:55:44 CEST 2008

Steven Toth wrote:
> Devin Heitmueller wrote:
>> Certainly I'm in favor of expressing that there is a preferred unit
>> that new frontends should use (whether that be ESNO or db), but the
>> solution I'm suggesting would allow the field to become useful *now*.
>> This would hold us over until all the other frontends are converted to
>> db (which I have doubts will ever actually happen).
> I'm not in favour of this.
> I'd rather see a single unit of measure agreed up, and each respective 
> maintainer go back and perform the necessary code changes. I'm speaking 
> as a developer of eight (?) different demod drivers in the kernel. 
> That's no small task, but I'd happily conform if I could.
> Lastly, for the sake of this discussion, assuming that db is agreed 
> upon, if the driver cannot successfully delivery SNR in terms of db then 
>   the bogus function returning junk should be removed.
> Those two changes alone would be a better long term approach, I think.

How about adding a new command instead (and a similar one for S2API)? 

/* Read SNR in units of dB/100 */
#define FE_READ_SNR_DB _IOR('o', 74, __u16)

Then it's no problem to slowly migrate the drivers to this interface. The
old interface can still stay for some time without changes. Applications
can try this ioctl, and if it returns an error, then it is not implemented
for the used device.


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