.TH USBDISK 4
.SH NAME
usbdisk, usbfat: - serve USB mass storage devices
.SH SYNOPSIS
.B usb/disk
[
.B -dDfl
] [
.B -m
.I mountpoint
] [
.B -s
.I srvname
] [
.I ctrlno
.I id
]
.LP
.B usbfat:
[
.B -fl
] [
.I disk
[
.I mntpt
] ]
.SH DESCRIPTION
.I Disk
serves a directory named
.I mountpoint
(default
.BR /n/disk )
containing the files
.B ctl
and
.IR n ,
where
.I n
is the number of a LUN to access,
for all detected LUNs of the named or found USB device.
.I Disk
searches for a USB device with class 8 (storage),
subclass 2 (ATAPI CD/DVD),
5 (removable, ATAPI-like) or
6 (SCSI transparent),
and
protocol 0x50 (bulk), or uses
.BI /dev/usb/ ctrlno / id
if specified.
In every LUN directory are the files
.B data
and
.BR raw .
.B data
gives read/write access to blocks of the device.
.B raw
is a raw SCSI-like interface (talk to it with
.IR scuzz (8)).
.PP
The root directory's
.B ctl
file accepts the command
.LR reset ,
which tells
.I disk
to again fetch the information about all LUNs,
and yields the device geometries when read.
.PP
The
.B -d
option generates debugging output.
The
.B -f
option avoids freaking out some cheap USB flash disks by not issuing
UMS reset commands to them.
The
.B -l
option asks the device for its maximum LUN.
By default,
.I disk
assumes a maximum LUN of zero, since some devices
get upset if you ask them for their maximum LUN.
Flash memory devices are likely to have multiple LUNs.
The
.B -m
option mounts the served hierarchy on
.I mountpoint
instead of
.BR /n/disk .
The
.B -s
option posts a mountable file descriptor as
.BI /srv/ srvname.
The
.B -D
option prints all 9P messages.
.SH EXAMPLES
Access the usual preformatted FAT partition:
.IP
.EX
% usb/usbd
% usb/disk -l
% disk/fdisk -p /n/disk/0/data
part dos 7 31559
% dossrv -f /n/disk/0/data:7 usbstorage
dossrv: serving #s/usbstorage
% mount /srv/usbstorage /n/d:
% ls -l /n/d:
alrw-rw-rw- M 39 bill trog 180364 Oct  5 18:14 /n/d:/9LOAD
d-rwxrwxrwx M 39 bill trog      0 Nov 13 14:30 /n/d:/benedict
.EE
.LP
The latter part of the above example, from
.B disk/fdisk
to
.BR mount ,
has been packaged up as
.IR usbfat: ,
which mounts the FAT file system in the DOS partition of the named
.I disk
(by default
.BR /n/disk/0/data )
on
.I mntpt
(by default
.BR /n/usb ).
.SH FILES
.TF /srv/usbsfs.ctlr.id
.TP
.B /n/disk
default mountpoint
.TP
.B /n/usb
default mountpoint for FAT file system on the disk
.TP
.B /srv/usbfat.$user
FAT file system service
.SH SOURCE
.B /sys/src/cmd/usb/disk
.br
.B /rc/bin/usbfat:
.SH SEE ALSO
.IR fs (3),
.IR sd (3),
.IR usb (3),
.IR prep (8),
.IR scuzz (8)
.SH BUGS
Should implement
.IR sd (3)'s
interface for each LUN.
Currently,
if there are multiple partitions, you can use
.IR fs (3)
to manage them.
If
.L "fdisk -p"
prints nothing,
there is no partition table on the device,
so one can invoke
.IR dossrv (4)
directly.
.PP
USB 1 flash disks' I/O rates are slow and variable.
Reading and writing in large units (e.g., 4KB) seems to be faster
by an order of magnitude when transferring large volumes of data.