Comments on: hotplug events for media changes?

By: textshell

textshell — Fri, 05 Jan 2007 23:49:24 +0000

I think there is some ioctl based way to get that, i did play around with some time ago… It’s not polling, the call blocks until an event is delivered (or maybe a signal to the process or such stuff). I found it in some programm out there, never seen any kind of proper documentation…
see http://people.redhat.com/davidz/cd_poll.c for sample code (it says poll in the comment, but it’s event based )

By: sven

sven — Fri, 05 Jan 2007 01:07:04 +0000

Kevin: That’s basically what I see as the problem: The kernel knows, but it won’t tell.
Glennie: inotifywait sounds like a good plan. I will try that. And since hdX/size should change any time the kernel detects a media change, this might work…. I’ll see.

By: Glennie

Glennie — Thu, 04 Jan 2007 22:53:21 +0000

Use inotify to detect if a CD is inserted.
Try inotifywait /sys/bloc/hdX/size. This works on SID and should be better than polling the drive…

By: Kevin Mark

Kevin Mark — Thu, 04 Jan 2007 19:03:21 +0000

This brings to mind the adage: if a tree falls in the forest and no one hears it, does it make a sound?
The kernel knows, but it wont make a ’sound’, so hotplug can’t know.
Is this a know bug? is it fixable?

By: sven

sven — Thu, 04 Jan 2007 15:54:26 +0000

Yes, KDE knows about the media change through hald, which in turn seems to use hald-addon-cdrom (or a similar name), which polls the CD drive. I’m not sure though how the polling is done.

By: James

James — Thu, 04 Jan 2007 15:50:15 +0000

I remember religiously uninstalling/deleting/nuking/going-in-with-a-scalpel-and-scraping-the-hard-disk-to-make-sure whatever utility used to do that “poll the CD evey second to check what’s in it, and log to syslog if it errors out because there’s nothing there.” Was it autofs, automount? Seems like I haven’t had to do that in a few years, but my Etch KDE still knows that a CD was inserted. So it is still polling the drive, and just leaving syslog alone? A step in the right direction!