This is the FDI data for the Sandisk Sansa m250 music player:

  <!-- Sandisk Corp. Sansa m250 (maybe others as well) -->
      <match key="@storage.physical_device:usb.vendor_id" int="0x0781">
        <match key="@storage.physical_device:usb.product_id" int="0x7401">
           <append key="info.capabilities"
type="strlist">portable_audio_player</append>
           <merge key="info.category" type="string">portable_audio_player</merge>
           <merge key="portable_audio_player.type" type="string">generic</merge>
           <merge key="portable_audio_player.access_method"
type="string">storage</merge>
           <merge key="portable_audio_player.storage_device"
type="copy_property">info.udi</merge>
           <append key="portable_audio_player.output_formats"
type="strlist">audio/mpeg</append>
           <append key="portable_audio_player.output_formats"
type="strlist">audio/x-ms-wma</append>
           <append key="portable_audio_player.input_formats"
type="strlist">audio/mpeg</append>
           <append key="portable_audio_player.input_formats"
type="strlist">audio/x-ms-wma</append>
           </match>
      </match>