Modifying mount points of USB Mass Storage devices

[Bill Paxton]

I hate asking these kinds of questions, I've read the archives and 
googled for a couple days but I can't figure it out on my own. Sorry.

So here we have a USB Mass Storage camera. I can tickle udev to make a 
snazzy device name for it, that works well but it's just cosmetic. The 
big deal comes from the fdi entry and the mount point. I don't care if 
it's /dev/sd? but I do care where it gets mounted.

The Mass Storage entities has all kinds of uniquely identifiables;
name, vendor, product, serial, etc.
I can make an entry something like:

---
<device>
 <match key="@storage.physical_device:info.bus" string="usb">
  <match key="@storage.physical_device:usb.vendor_id" int="0x12345">
    <match key="@storage.physical_device:usb.product_id" int="0x12345">
     <merge key="volume.policy.desired_mount_point" 
type="string">foo</merge>
    </match>
  </match>
 </match>
</device>
---

hotplug and udev and hal are all working fine...
... but fstab-sync makes the mount point /media/usbdisk

And it does make those entries in the corresponding udi when you check 
it with lshal. But that's not where the actual mount is; it's a parent 
device.

When looking at lshal, it's like the uniquely identifiable part is the 
overall drive structure and the actual data partition has absolutely 
nothing to I.D. it with other than the volume number and size:

---
udi = '/org/freedesktop/Hal/devices/volume_part1_size_262118912'
  info.callouts.remove = {'fstab-sync'} (string list)
  info.callouts.add = {'hald-add-selinux-mount-option', 'fstab-sync'} 
(string list)
  volume.policy.desired_mount_point = 'usbdisk'  (string)
  volume.policy.mount_filesystem = 'vfat'  (string)
  volume.policy.should_mount = true  (bool)
  info.udi = '/org/freedesktop/Hal/devices/volume_part1_size_262118912'  
(string)
  volume.partition.msdos_part_table_type = 6  (0x6)  (int)
  info.product = 'Volume (vfat)'  (string)
  volume.size = 262118912  (0xf9f9e00)  (uint64)
  volume.num_blocks = 511951  (0x7cfcf)  (int)
  volume.block_size = 512  (0x200)  (int)
  volume.partition.number = 1  (0x1)  (int)
  info.capabilities = {'volume', 'block'} (string list)
  info.category = 'volume'  (string)
  volume.is_partition = true  (bool)
  volume.is_disc = false  (bool)
  volume.is_mounted = false  (bool)
  volume.mount_point = ''  (string)
  volume.label = ''  (string)
  volume.uuid = ''  (string)
  volume.fsversion = 'FAT16'  (string)
  volume.fsusage = 'filesystem'  (string)
  volume.fstype = 'vfat'  (string)
  block.storage_device = 
'/org/freedesktop/Hal/devices/storage_model_USB_DRIVEUNIT'  (string)
  block.is_volume = true  (bool)
  block.minor = 17  (0x11)  (int)
  block.major = 8  (0x8)  (int)
  block.device = '/dev/sdb1'  (string)
  linux.hotplug_type = 3  (0x3)  (int)
  info.parent = 
'/org/freedesktop/Hal/devices/storage_model_USB_DRIVEUNIT'  (string)
  linux.sysfs_path_device = '/sys/block/sdb/sdb1'  (string)
  linux.sysfs_path = '/sys/block/sdb/sdb1'  (string)

---

I need to refer to some of the elements listed in info.parent udi, 
apparently, because there's not a single thing uniquely identifiable 
here. Using the volume number and the partition size is unacceptable.

This is a child of the device that contains all the goodies that I can 
use to uniquely identify this particular device. So there's got to be a 
method to have the child inherit or at least refer. Right? This can't be 
as hard as I'm making it, but the archives show lots of similar questions.

All I want to do is control the mount point of any media; that's ANY 
media, any size, any format, anything, by the fact that it's being 
served up from a USB Mass Storage device from vendor_id 0x12345 
product_id 0x12345 (and/or other unique identifiers.)

Any help appreciated. Thanks for reading.


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