[linux-dvb] Re: setting voltage takes TONS of time

[jhall@UU.NET (Jeremy Hall)]

what about if I do the following:

check for invalid permissions (RDONLY) then

stopfilt()
then return to userspace
next userspace call executes the return secSetVoltage 8 times

then setPIDS (0,0,0,0,0)

I can run setpids before starting hte command as well, but I am trying to
avoid it during the command.  stopfilt() doesn't seem to take much time at
all.

_J

In the new year, Johannes Stezenbach wrote:
> On Wed, Jul 31, 2002 at 07:01:01AM -0400, Jeremy Hall wrote:
> > It's a Hauppauge DVB/S card.  I can try each patch applied individually,
> > instead of all the patches at once and see what the times are, but this
> > machine must run LL tasks and they have real-time constraints.
> > 
> > I need the firm timers patch because I am trying to sleep for 8ms and only
> > 8 ms.  Is the line:
> > 
> > setPIDS (0,0,0,0,0);
> > 
> > really necessary? I can get under 8ms if I remove that.  But I'm not going
> > to do anything until I have a good game plan.  What is the recommended way
> > to attack this?
> 
> Sorry, I should've read your mail more carefully.
> 
> 11ms for SEC_SET_VOLTAGE is considered normal, as communication
> with the ARM processor on the DVB-S card is required as well as
> I2C bus transactions to the QPSK demodulator (which drives the
> LNB voltage control).
> 
> If you invalidate the transport stream by SEC_SET_VOLTAGE, you must
> shut down the PES filters and/or MPEG decoder first, as the ARM
> might crash when it gets invalid TS data. The setPIDS(0,0,0,0,0) does
> that. So it cannot be omitted, but maybe it might help you to
> split the operation in two parts to meet your 8ms contraint?
> 
> 
> Johannes
> 
> 
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