Re: [Nolug] camera card reader

On Feb 27, 2004, at 18:09, Ron Johnson wrote:
> Ah, autofs.
>
> Then I wonder what is the difference between usbmgr and hotplug?
>
> According to Debian, usbmgr and hotplug conflict with each other.

<disclaimer>
This is all how I understand it only. Some or all of it may be wrong
:-)
</disclaimer>

usbmgr was written when USB support was first added to the kernel, both
for adding modules and for running support code. It was designed as a
daemon that periodically polls /proc/bus/usb/devices, and does its
thing when finding a new device there. I'd imagine (my own guess here)
that it was done that way because it was probably the easiest and least
intrusive way at the time. Anyway, for usbmgr to work, you need usb
support and preliminary usb device filesystem compiled in, as well as
whatever individual drivers you want, as modules.

When other devices needed hot-swap support too, it became obvious that
a more general solution was needed. So, the kernel hackers introduced
a new config option (CONFIG_HOTPLUG) for hotplug support, and made
various kernel subsystems use the hotplug system to call the executable
listed in /proc/sys/kernel/hotplug (usually "/sbin/hotplug") for
configuration changes. So, as well as being a more general solution
(and one the kernel explicitly supports), hotplug is more efficient, as
it replaces the polling mechanism with a notification mechanism. For
this to work, of course, you have to compile in hotplug support, as
well as compile whatever drivers you need as modules.

Hope this helps,
Kevin

___________________
Nolug mailing list
nolug@nolug.org
Received on 02/28/04