Using udev-extras for hardware-specific quirks?
martin.pitt at ubuntu.com
Wed Jun 3 09:56:05 PDT 2009
Daniel D Streetman [2009-06-03 10:48 -0400]:
> Well that is the problem, isn't it? With serial ports there is absolutely
> nothing to go on to tell what physical port it is except for numbering.
Right, that might be more tricky. I actually can't test it here, it's
been a long time since I had a machine with a real serial port.
> Well, I don't think this will work as the problem isn't consistent naming -
> serial ports are not added/removed and so there is no danger of
> inconsistent numbering
I wouldn't rely too much on it. Ethernet cards aren't added/removed
either, and yet without the persistency rules they get a pretty much
random order on boot. I guess the ordering is more reliable for serial
ports since they are all covered by the same driver (unlike the two
ethernet cards I used to have).
> I could create permanent "persistent naming" rules such as the above one to
> correctly number the ports, but I don't think that is what you mean - you
> mean I should create a dynamic rule to create those persistent naming rules
> on-the-fly as serial ports are (first) detected. That is what you mean
Not really on the fly, just attaching the name to a physical attribute
which stays constant across reboots. If there is none, then I guess
you can keep your current rules which just rename the interfaces.
> Also to clarify, I'm not looking to create a rule for just my system - I am
> trying to create a permanent rule that I can upstream into a common
> repository that all distributions can draw from so the various quirks on
> these systems can be correctly handled by all distributions.
Right, I understood your intention, but I don't think we want
arbitrary renaming like that, since they are going to have a different
effect on every machine anyway, and one order is as good as the other
> With serial ports? How can an application not rely on the serial port
> number? For other types of interfaces, USB devices, ethernet interfaces,
> displays, whatever - I can understand that. But ever since serial ports
> were invented, the port number is the one and only thing the application
> can use. Right?
Right, that's true. Probably one of the reasons why they are
Usually, when there is a device on a port, there is often a way to
probe that device instead of the port it is attached to (which is what
you actually want in most cases). That needs an external probe program
with RUN/IMPORT, and is very specific to the type of hardware you
> For PCI-card based serial ports, there are no other device properties
> besides the PCI address and kernel-assigned name.
The PCI device should have an unique physical slot name
(PCI_SLOT_NAME), but that won't help you, since I guess one PCI device
drives all of your serial ports?
So I think you should either locally keep your current renaming, or
perhaps just swap the stickers to have the correct number :)
Martin Pitt | http://www.piware.de
Ubuntu Developer (www.ubuntu.com) | Debian Developer (www.debian.org)
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