.SH NAME
lab 6 - signal modules; implement filter (again) 
for signalfs and test 
the recursiveness of the file server.
.SH SETUP
Inferno 4th Edition 20040830. See also labs 4 an 5.
.SH DESCRIPTION
.SS "2004/0922 21:24
Changed filter.b to use the clone interface.
The
.I ctl
file accepts a 
.B source
command which takes a filename or another signal
source which may be served by the same signalfs
.IP
.EX
% echo source /usr/caerwyn/lab/6/mnt/wave > mnt/filter/2/ctl
.EE
.PP
The filter module then opens
.I ctl
reads the number of the conversation directory and then
opens 
.IR data .
The filter is then responsible for setup of the signal source.
It should probably pass through commands written to 
.I ctl
that it does not understand, so the wave can be controlled
through the filter 
.IR ctl .
.PP
I made a small change to
.B signalfs.b
to not fork the namespace so the mount of the server
affects the current process and the filter module
is able to access the wave
.IP
.EX
176c178
< 	pidc <-= sys->pctl(0, nil);
---
> 	pidc <-= sys->pctl(Sys->FORKNS, nil);
.EE
.PP
.SH CONCLUSION
The recursion (if that's the right term) works.
Filter reads data from wave served by the
same file server; or it could be a different file
server running remotely.
.PP
This was a quick lab session to resolve
my doubts about signalfs. Need to really
start implementing all the filters. Especially
those that combine multiple sources.
.SH FILES
.A http://caerwyn.com/lab/6/dsp.b dsp.b
.A http://caerwyn.com/lab/6/dsp.m dsp.m
.A http://caerwyn.com/lab/6/envelope.b envelope.b
.A http://caerwyn.com/lab/6/filter.b filter.b
.A http://caerwyn.com/lab/6/noise.b noise.b
.A http://caerwyn.com/lab/6/signal.m signal.m
.A http://caerwyn.com/lab/6/signalfs.b signalfs.b
.A http://caerwyn.com/lab/6/wave.b wave.b