HAL ejects

[David Zeuthen]

On Tue, 2005-01-25 at 11:01 +0200, Paul Ionescu wrote:
> Hi,
> 
> On Tue, 25 Jan 2005 08:48:56 +0100, Peter Backlund wrote:
> > Here's something I'd like to see in FC4: unmount-on-eject via HAL. I'm
> > talking about automatic unmounting CD/DVD when you press the eject button,
> > like the ancient "supermount". Is this within the scope of HAL?

Most drives don't report "eject button pressed" asynchronously - some HP
drives do, some others as well, but not a lot. We *could* make hal catch
this signal (if the drive supports it) and propagate it all the way of
the stack; it would look like this

 1. Eject is pressed; door doesn't open
 2. (up to 0.999.. seconds later) hald is notified that someone
    pressed eject; hald broadcasts a signal
 3. gnome-vfs (or whatever) catches the signal and sends out the
    preunmount signals
 4. apps close their open files and ACK's the preunmount
 5. gnome-vfs unmounts the drive; if there are still apps with
    open fd's the unmount fails. gnome-vfs puts up nice dialog.
 6. door is unlocked; disc is ejected

But since only few drives support this I'm not happy about providing
two different user experiences.

> It is already in FC3 
> I am using it right now.
> I think it is not in HAL, but in GVM.
> However, to be able to use it, you have to disable "lock on mount" option
> of cdrom by "echo 0 > /proc/sys/dev/cdrom/lock"
> or putting "dev.cdrom.lock = 0" in /etc/sysctl.conf and reloading with
> sysctl -p.
> 

No, that's bad advice. What happens in that setup is the following

 1. Eject is pressed; door opens
 2. hald polls for media; oops no media
 3. hald lazy unmounts /dev/cdrom - the media is gone so we have to
    deal with it somehow; it's better than doing nothing
 4. all your programs with open fd's on /media/cdrom is screwed

It's get even more fun if you're writing to the CD. 

The real solution  is to use something along the lines of volumagic
which is like supermount but only in userspace.

David