Documentation/usb/mass-storage.rst

9   appearing to the host as a disk or a CD-ROM drive.  It supports
12   to read-only, and gadget can indicate that it is removable and/or
13   CD-ROM (the latter implies read-only access).
15   Its requirements are modest; only a bulk-in and a bulk-out endpoint
17   Support is included for full-speed, high-speed and SuperSpeed
20   Note that the driver is slightly non-portable in that it assumes
21   a single memory/DMA buffer will be usable for bulk-in and bulk-out
29   (which is no longer included in Linux).  It will talk only briefly
30   about how to use MSF within composite gadgets.
38   - file=filename[,filename...]
53     simulating CD-ROM, block size of the device if the backing file is
56   - removable=b[,b...]
71     is loaded.  The same applies if the module is built in, no
82     ejected or removed (as is true for a CD-ROM drive or a card
85     “hot-unpluggable”.
87   - cdrom=b[,b...]
90     CD-ROM.  The default is false.
92   - ro=b[,b...]
99     backing file could not be opened in read/write mode, the gadget
102     The default value for non-CD-ROM logical units is false; for
103     logical units simulating CD-ROM it is forced to true.
105   - nofua=b[,b...]
107     This parameter specifies whether FUA flag should be ignored in SCSI
110     MS Windows mounts removable storage in “Removal optimised mode” by
112     achieved by setting the FUA (Force Unit Access) bit in SCSI
115     aggregation in block layer dramatically decreasing performance.
123   - luns=N
130     in “file” argument is greater then the value of “luns”, all excess
134     be deduced from the number of files specified in the “file”
138   - stall=b
144   In addition to the above, the gadget also accepts the following
145   parameters defined by the composite framework (they are common to
146   all composite gadgets so just a quick listing):
148   - idVendor      -- USB Vendor ID (16 bit integer)
149   - idProduct     -- USB Product ID (16 bit integer)
150   - bcdDevice     -- USB Device version (BCD) (16 bit integer)
151   - iManufacturer -- USB Manufacturer string (string)
152   - iProduct      -- USB Product string (string)
153   - iSerialNumber -- SerialNumber string (string)
158   For each logical unit, the gadget creates a directory in the sysfs
161   - file
171     with the Prevent-Allow Medium Removal SCSI command.
173   - ro
179   - nofua
184   - forced_eject
188     it.  The content doesn't matter, any non-zero number of bytes
189     written will result in ejection.
200   mass storage protocol.  As a composite function, MSF may be used by
203   All of the information in previous sections are valid for other
209   For examples of how to include mass storage function in gadgets, one
218   that MSG is a composite gadget (ie. uses the composite framework)
223   (ii) MSF can be used in any other composite gadget.
225   Because of that, File Storage Gadget has been removed in Linux 3.8.
229   1. In FSG the “removable” and “cdrom” module parameters set the flag
230      for all logical units whereas in MSG they accept a list of y/n
236      parameters are handled in MSG by the composite layer's parameters