Johannes Erdfelt wrote:
> On Thu, Apr 13, 2000, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> [SNIP]
> I want mouse A to always be named mouse0, and mouse B to always be named
> mouse1, EVEN if I connect mouse B in first. It should be named mouse1
> and mouse0 should be empty.
>
Why? mouse0 and mouse1 are kernel labels that are assigned based on which
device was found first, same with eth0 and eth1.
>
> > > Everyone seems to want to solve a specific problem but there's a larger
> > > bigger problem everyone seems to be overlooking.
> >
> > And several small specific solved ones people keep missing too
>
> But they are irrelevant. They don't solve the overall problem. You can
> keep naming these specific solutions, but they still don't solve the
> problem for every device.
>
> Solving the problem on a per device basis doesn't make any sense for the
> simple fact that it's specific to one device.
>
Sure it does, unless there is some generically unique identifier that every
piece of hardware has. I'll give you a hint: There isn't one! To determine
one ethernet card from another, one may consider using the MAC address, or
maybe the manufacturer+serial. For PCs with USB, MAC address would be fine,
two cards with the same MAC is a broken concept on PCs. However, other
architectures may need to rely on Manufacturer+SerialNumber to correctly
identify one card from another.
That is just ethernet. Then there are mice. I assume with a mouse you could
use Manufacturer+Serial to determine which mouse it is. Probably same thing
with a lot of other USB devices too (is this part of the USB standard??).
Assuming there is some standard USB way of differentiating one device for
another, then by all means use it, but don't expect the kernel to use it.
Identifying one mouse from another, or one keyboard from another, or one
graphics card from another, or one "foo" from another is a user space issue.
Use something like Red Hat's "kudzu" to take care of this. If you would like,
you can even make symlinks and stuff like that. For instance, have a
/dev/aliases directory (making this up) which has symlinks such as:
mouse0->/dev/usb/mouse0, mouse1->/dev/usb/mouse2, mouse2->/dev/usb/mouse1.
Have a user daemon take care of identifying hardware and have it update the
/dev/aliases directory with appropriate symlinks. If a device is not
connected, then I would recommend its symlink be removed and then replaced
when it is reconnected.
This is just an example, I have no idea if those device names are correct,
I am still running 2.2.15pre and I don't have any USB devices. I strongly
believe that kernel device numbers should remain just that: kernel device
numbers. However, to avoid having to come up with some sort of way to check
which device is which, I recommend the symlink solution above (or some other
standard user space thing) to handle all of that.
[SNIP]
>
>
> I think that devfsd can be part of the solution, but it's far from it
> now.
>
Yes, you could use devfsd to handle this, or you could create another daemon
(probably a better idea, one program, one purpose) to handle the device
mappings. Of course devfsd and the fictional program I mention are sort of
similar I guess.
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This archive was generated by hypermail 2b29 : Sat Apr 15 2000 - 21:00:23 EST