Re: [linux-usb] Re: USB device allocation

Nathan Hand (nathanh@chirp.com.au)
Sun, 10 Oct 1999 00:30:06 +1000


On Fri, Oct 08, 1999 at 03:26:39PM -0400, Theodore Y. Ts'o wrote:
>
> If the user plugs in a USB modem, the user knows they plugged in a modem,
> they run their getty/pppd/minicom on the new modem device.
>
> What's the difference between saying this and saying, "If the user plugs
> in a USB modem, they know they have plugged in a modem, and they can
> type the appropriate mknod command as root"? Why is it Too Hard and
> Unfair to force a user to type a mknod command, but it's OK to force
> them to edit /etc/ttys or /etc/ppp/options?

This paragraph sums up the crux of the argument, and eloquently says
what hpa and alan said in the last devfs flamefest.

Devfs as a filesystem doesn't do enough. You still need a user space
daemon to do more complex things. For example, plugging in a hotswap
isdn card shouldn't just create /dev/ppp, it should also fire up the
ifconfig and pppd processes. There are other (better) examples.

And once you admit you need a user space daemon, then you can accept
that you don't *need* devfs as a filesystem. You can achieve most of
devfs's functionality using a user space daemon. I particularly like
your idea of select/poll on /proc/devices.

But keep in mind that updating /dev is likely to be only a tiny part
of what this daemon would ultimately do. It could also start scripts
to mount drives, configure ports, restore defaults, upload flashcode
to devices, configure networks, notify userspace processes, etc.

Similarly to cardmgr/PCMCIA already.

-- 
Nathan Hand - Chirp Web Design - http://www.chirp.com.au/ - $e^{i\pi}+1 = 0$
Phone: +61 2 6230 1871   Fax: +61 2 6230 1515   E-mail: nathanh@chirp.com.au

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