Re: [Utopia] persistent partition naming

[David Zeuthen <david fubar dk>]

On Fri, Apr 23, 2004 at 11:27:35AM +0200, Kay Sievers wrote:
> Hey, nice to have this 'good place' instead of zapping through the blogs.
> ("utopia" can be read as the greek "eu topos" and means "good place", or
> "ou topos" which means "no place") :)
> 

Heh, nice to see you here Kay.

> I would really like a feature in the device handling stack,
> that mounts the partition of a removable device everytime on the same
> place in the filesystem, regardless of the connection order.
> 
> If I plug in my usb-stick-mp3-player, it would be nice if my favorite
> audio player can access the filesystem by remembering the path to it.
> Yes, I use a udev-rule, but the average user is not expected to do this.
> 
> I tried a udev callout which handles all uncatched partitions, generates
> a name for a symlink and finally creates a rule-file in /etc/udev/rules.d/
> with the device serial number. So the next time the device appears, this
> rule will catch it.
> But I'm not really happy with it. What is the right place to do something
> like this?  What do you think?
> 

I really agree it would be nice to have both persistent and sane mount point
names. The thinking right now is to use hal-callouts; for a very simple
example see here

  http://freedesktop.org/cgi-bin/viewcvs.cgi/hal/hal/tools/callouts/fstab-update.sh?rev=1.4&view=auto

This example just uses the major/minor numbers to create mount point names
a'la /mnt/hal/disk-%d-%d- which is, ahem, not nice. What could be nice was
something along the lines of

 /mnt/cdrom
 /mnt/cdrw
 /mnt/dvd+r
 /mnt/dvd-r
 /mnt/compact_flash
 /mnt/memory_stick
 /mnt/smart_media
 /mnt/ipod_firmware
 /mnt/ipod_data

and I think by now HAL can actually export enough information[1] for this
to be possible to implement. 

So, my answer would be to implement this as a hal callout that examines all
the information exported by HAL (btw, the spec is far behind the code
(I'll change this soon) so the best source is the source-code) and possibly
maintain a database for remembering the the volume name. An open question
is whether the mountpoint name is tied to the actual volume or the reader
in which the volume is inserted? 

Btw, the problem is closely tied to how to choose an icon and name to
present in Nautilus so perhaps code can be shared there.

Oh, and IMO an audioplayer application shouldn't have to remember the path
to the device. A mp3 player device should be matched with a fdi file 
(possibly the user can use a device browser to match it manually) and be
marked with the capability 'music_player'. This way g-v-m can automatically
start the application. Here's how I match my non-usb-storage based camera

 http://freedesktop.org/cgi-bin/viewcvs.cgi/hal/hal/fdi/20freedesktop/canon-digital-ixus-v.fdi?rev=1.1&view=auto

it would look much the same for my usb-storage mp3 player.

Cheers,
David

[1] : In fact, AFAIK it's not possible to identify stuff like memory_stick,
compact_flash or smart_media. But we can use a device information file to
remedy this sitution. Here's an example for my 6in1 card reader

 http://freedesktop.org/cgi-bin/viewcvs.cgi/hal/hal/fdi/20freedesktop/6in1-card-reader.fdi?rev=1.1&view=auto

Of course, without a file like this we don't know nearly as much.