Am Donnerstag, 30. Juni 2005 21:56 schrieb Christian Magnusson:
> You are right... The kernel thinks the usb adapter is physically
> removed and then inserted again and get a new device number.
> This problem is very fatal and question is if such thing should
> be handled by owfs.
>
Hm. owserver does handle the whole 1-Wire tunneling. If it could not handle
exceptional situations, like network breakdown, by itself it has very few
benefits to use it.
In that case, I would have to implement a secondary client-server-connection,
which detects at least the errors correctly. In such a setup, owserver is no
longer needed because my connection could transfer the 1-Wire data, too.
> It could of course be added to detect a new
> 1-wire adapter if it disappears, but strange things can happen.
>
Does this apply if the hardware of the machine is not touched?
> Have you heard about any printer or scanner driver which solve the
> issue of a disconnected device?
>
That's a different world: home or small office appliances are known to fail
often, most times beyond repair.
That's totally different from a commercial or industrial automation
environment, where anthing must work as long as possible and any error that
could be recovered from automatically must be recovered automatically.
And sure, I can think of a driver which recovers from failures itself: TCP.
I think it's best to solve this issue inside owserver. It is a network
component and networks fail if someone pulls the cable.
BTW: A backup ethernet connection for owserver is something to think of - I
don't need it for now, but this is really hot in high-available automation
environments.
> Let say you have 2 DS9490 adapters. (Called A & B)
> Start: owfs -p19160 -u /var/1wire
> /var/1wire/system/adapter/name.0 = DS9490 (The first found adapter A)
>
> If adapter A get a hard error (like you) or is physically removed and
> inserted, the second adapter B will easily replace the first adapter
> which disappeared. It's perhaps possible to solve in some way, but I
> hope you understand this issue I see as a problem.
>
What miserably fails in that situation? From the owfs point of view, it's
totally indifferent on which adapter a chip connects - they are all put into
one directory tree.
The only situation I can think of this as a problem is with several owservers,
where each one connects to a different adapter, and the chips keep seperated
all up the line, even in the applications - and that's a setup which hardly
anybody would use.
> My usb-adapter have a unique id 81.01010101010101 which could be used to
> find the same adapter when re-connected, but does every adapter have
> a unique id? I thought there where old adapters without this feature...
>
The passive ones don't have. But it's only a small problem anyway, as the
passive adapters won't get you into "USB disconnect" troubles.
Kind regards
Jan
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