Many Linux systems will not be able to use it, since they only have PC-style USB Host (master) hardware in a PC, workstation, or server.
http://www.linux-usb.org/gadget/
To get an official response, post a feature request in the bugtracker asking for them to be included.
]]>$ find /lib/modules/3.8.8-2-ARCH/kernel/ -name 'g_*'
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_ffs.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_hid.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_ether.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_audio.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_ncm.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_midi.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_webcam.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_printer.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_dbgp.ko.gz
/lib/modules/3.8.8-2-ARCH/kernel/drivers/usb/gadget/g_serial.ko.gz
g_file_storage or g_mass_storage module is not found in 3.8.8-2 as well
]]>these updates are pretty recent - so I think the module src should be there I guess - right?
maybe archlinux kernel & module package (compilation) misses this module somehow?
/lib/modules/3.8.7-1-ARCH/kernel
└─$ find . -name 'g_*'
./drivers/usb/gadget/g_ether.ko.gz
./drivers/usb/gadget/g_audio.ko.gz
./drivers/usb/gadget/g_ffs.ko.gz
./drivers/usb/gadget/g_ncm.ko.gz
./drivers/usb/gadget/g_dbgp.ko.gz
./drivers/usb/gadget/g_printer.ko.gz
./drivers/usb/gadget/g_hid.ko.gz
./drivers/usb/gadget/g_serial.ko.gz
./drivers/usb/gadget/g_midi.ko.gz
./drivers/usb/gadget/g_webcam.ko.gz
$ uname -a
Linux my-vaio 3.8.7-1-ARCH #1 SMP PREEMPT Sat Apr 13 09:01:47 CEST 2013 x86_64 GNU/Linux
$ modinfo g_file_storage
modinfo: ERROR: Module g_file_storage not found.
$ modinfo g_mass_storage
modinfo: ERROR: Module g_mass_storage not found.