Date: Fri, 07 Jan 2000 23:51:14 +0100
From: Carlo Scarfoglio <[EMAIL PROTECTED]>
Now I am running kernel 2.3.36 SMP , Suse 6.1 standard on a dual
Celeron Abit BP6 mobo. The serial dongle is connected to /dev/ttyS3
on an ISA multiport card.
I ran the app through strace on K 2.3.36 and after a write to the
serial port the result was an endless series of read(4, 0x.......,84)
that failed wit error -1. From time to time some characters are
returned, but the app probably does not receive enough data to
perform its check. Interestingly, when run under strace, the app
finds and checks OK the dongle, it won't when run alone (no strace).
But yesterday I found that I can fix the problem by setting
"low_latency" to the port with setserial. This seems to be the cure
so far.
It sounds like the Dongle protocol is extremely fragile, and is highly
timing dependent. For what it's worth, old Linux kernels (Linue 2.0)
had basically the same behaviour as newer kernels by default. The
low_latency flag turns on new behaviour, which increases CPU
utilization, but shortens the time before incoming characters are
processed.
If using low_latency fixes it, as well as running the app under strace
(which slows the application), then it's probably a very fragile
application or hardware, and it's not a kernel problem. Your app vendor
is going to have to deal with this.
- Ted
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