[linux-dvb] Re: blocking FE_SET_FRONTEND ioctl in non-blocking mode

[Andrew de Quincey <adq_dvb@lidskialf.net>]

On Wednesday 12 May 2004 13:38, Ragnar Sundblad wrote:
> --On den 12 maj 2004 11:57 +0100 Andrew de Quincey <adq_dvb@lidskialf.net>
>
> wrote:
> >> Full ACK. The frontend API is specified to be asynchronous, if
> >> userland sets filters before the frontend reports successful
> >> tuning it's its own fault.
>
> I am not sure that is what happened, I think you could get
> stale data anyway.
>
> >> IMHO the code must be removed, because some software relies
> >> on the non-blocking behaviour of FE_SET_FRONTEND.
> >
> > OK - I'll look into it this evening.
>
> Please make it not deliver stale data on sync calls at least.
>
> It is like opening a socket and first getting some old data
> from the previous socket user. I think that is a bad API.

Hmmm yeah - the difference here is that we can close + reopen the "socket" 
without having to retune... so the driver can't know whether the user wants 
to open+use the previous frontend lock, or open+retune.

I agree stale data is bad - thats why I added it. I wouldn't have thought it 
would take 2 seconds to kick off a frontend tune though. I'll do some speed 
tests on the CVS code tonight.


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