As requested (http://gnomedesktop.org/node/2609), here's a bug report to add
playlist support for my portable audio player named Archos Gmini 120.

The device uses UMS and the music is stored in the Music directory. It can use a
proprietary manager for the library but I don't use it as it plays just fine m3u
playlists.

I've filled a bug report for HAL as it did not detect it as a portable audio
player: https://bugs.freedesktop.org/show_bug.cgi?id=6139

Here are the information you've asked for:
0: udi = '/org/freedesktop/Hal/devices/volume_uuid_9482_04AC'
  volume.unmount.valid_options = { 'lazy' } (string list)
  volume.mount.valid_options = { 'ro', 'sync', 'dirsync', 'noatime',
'nodiratime', 'noexec', 'quiet', 'utf8', 'shortname=', 'codepage=',
'iocharset=', 'umask=', 'dmask=', 'fmask=', 'uid=' } (string list)
  org.freedesktop.Hal.Device.Volume.method_execpaths = {
'hal-system-storage-mount', 'hal-system-storage-unmount',
'hal-system-storage-eject' } (string list)
  org.freedesktop.Hal.Device.Volume.method_signatures = { 'ssas', 'as', 'as' }
(string list)
  org.freedesktop.Hal.Device.Volume.method_names = { 'Mount', 'Unmount', 'Eject'
} (string list)
  info.interfaces = { 'org.freedesktop.Hal.Device.Volume' } (string list)
  volume.ignore = false  (bool)
  info.udi = '/org/freedesktop/Hal/devices/volume_uuid_9482_04AC'  (string)
  volume.partition.msdos_part_table_type = 12  (0xc)  (int)
  info.product = 'JUKEBOX'  (string)
  volume.size = 19987398144  (0x4a7577e00)  (uint64)
  volume.num_blocks = 39037887  (0x253abbf)  (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 = true  (bool)
  volume.mount_point = '/media/JUKEBOX'  (string)
  volume.label = 'JUKEBOX'  (string)
  volume.uuid = '9482-04AC'  (string)
  volume.fsversion = 'FAT32'  (string)
  volume.fsusage = 'filesystem'  (string)
  volume.fstype = 'vfat'  (string)
  storage.model = ''  (string)
  block.storage_device =
'/org/freedesktop/Hal/devices/storage_serial_USB_HS_IC25N020ATMR04_0_2411041000E7'
 (string)
  block.is_volume = true  (bool)
  block.minor = 1  (0x1)  (int)
  block.major = 8  (0x8)  (int)
  block.device = '/dev/sda1'  (string)
  linux.hotplug_type = 3  (0x3)  (int)
  info.parent =
'/org/freedesktop/Hal/devices/storage_serial_USB_HS_IC25N020ATMR04_0_2411041000E7'
 (string)
  linux.sysfs_path_device = '/sys/block/sda/sda1'  (string)
  linux.sysfs_path = '/sys/block/sda/sda1'  (string)

1: udi =
'/org/freedesktop/Hal/devices/storage_serial_USB_HS_IC25N020ATMR04_0_2411041000E7'
  block.storage_device =
'/org/freedesktop/Hal/devices/storage_serial_USB_HS_IC25N020ATMR04_0_2411041000E7'
 (string)
  info.udi =
'/org/freedesktop/Hal/devices/storage_serial_USB_HS_IC25N020ATMR04_0_2411041000E7'
 (string)
  storage.requires_eject = true  (bool)
  storage.hotpluggable = true  (bool)
  info.capabilities = { 'storage', 'block' } (string list)
  info.category = 'storage'  (string)
  info.product = 'IC25N020ATMR04-0'  (string)
  info.vendor = 'USB-HS'  (string)
  storage.removable = false  (bool)
  storage.physical_device =
'/org/freedesktop/Hal/devices/usb_device_e79_1201_2411041000E7_if0'  (string)
  storage.lun = 0  (0x0)  (int)
  storage.firmware_version = '0.01'  (string)
  storage.serial = 'USB-HS_IC25N020ATMR04-0_2411041000E7'  (string)
  storage.vendor = 'USB-HS'  (string)
  storage.model = 'IC25N020ATMR04-0'  (string)
  storage.drive_type = 'disk'  (string)
  storage.automount_enabled_hint = true  (bool)
  storage.media_check_enabled = false  (bool)
  storage.no_partitions_hint = false  (bool)
  storage.bus = 'usb'  (string)
  block.is_volume = false  (bool)
  block.minor = 0  (0x0)  (int)
  block.major = 8  (0x8)  (int)
  block.device = '/dev/sda'  (string)
  linux.hotplug_type = 3  (0x3)  (int)
  info.parent =
'/org/freedesktop/Hal/devices/usb_device_e79_1201_2411041000E7_if0_scsi_host_scsi_device_lun0'
 (string)
  linux.sysfs_path_device = '/sys/block/sda'  (string)
  linux.sysfs_path = '/sys/block/sda'  (string)

Hope this helps. Please do not hesitate to ask for more if it was not sufficient.