[Owfs-developers] OWFS concurency

[Nicolas H. <nhu...@gh...>]

I plan my application to have multiple little scripts that access the 
directory tree. Since the 1-wire is inherently unique and exclusive, I 
must not be able to access two devices at the same time.

This is currently the case, with various impact. Here is a little test 
that run many (2) $t/tempC in parallel :

[nhuillard@palma:devices]$ for t in 10.*; do (echo $t $(cat $t/tempC)& 
); done
cat: 10.26FE46000800/tempC: Invalid argument
10.26FE46000800
10.E42257000800 22.8125

[nhuillard@palma:devices]$ for t in 10.*; do (echo $t $(cat $t/tempC)& 
); done
cat: 10.26FE46000800/tempC: Invalid argument
10.26FE46000800
cat: 10.E42257000800/tempC: Invalid argument
10.E42257000800

[nhuillard@palma:devices]$ for t in 10.*; do (echo $t $(cat $t/tempC)& 
); done
cat: 10.26FE46000800/tempC: Invalid argument
10.26FE46000800
10.E42257000800 22.8125

As you can see, there is either an "Invalid argument" on one 1820, or on 
both.
When the $t/tempC are slightly desynchronized (when I type the command 
on two terminals, with a longer delay), one 1820 might return a 85°C 
reading, indicating a wrong conversion.

A mono-threaded OWFS (like OWHTTDP) might be useful.

NH