Information Technology Reference
In-Depth Information
One point of confusion relating to the mass-storage support under Win-
dows is Windows' support for Autoplay (previously called Autorun).
Autoplay enables the operating system to run a program, play a movie, or
perform other actions when a disk or other removable media is inserted. To
support Autoplay, a USB flash drive must contain a startup application and
an autorun.inf file that identifies the application. For operating systems pre-
vious to Windows XP SP2, the drive must report that it has non-removable
media in the response to a SCSI INQUIRY command. Chapter 6 has more
about the INQUIRY command.
Flash drives that incorporate U3 smart drive technology can hold a self-con-
tained application that runs on a Windows PC without having to install the
application on a hard drive, make registry changes, or reserve other system
resources. Running an application from a U3 drive copies temporary files to
the host computer,. The temporary files run the application and disappear
when the application closes. U3 is an open standard developed by SanDisk
and M-Systems. More information and development kits are at
www.u3.com.
A similar technology is available in the Ceedo portable oper-
ating system from Ceedo Technologies.
Linux
Linux has two drivers that support communications with USB mass-storage
devices. The usb-storage driver in Linux/drivers/usb/storage supports a wide
range of devices and has fast performance. The ub driver in Linux/driv-
ers/block/ub.c focuses on reliable operation but is slower and doesn't sup-
port as many devices. The ub driver supports only the bulk-only transport
protocol and PDT = 00h, doesn't try to accommodate non-compliant
devices, uses its own SCSI stack, and waits for each USB request block
(URB) to complete before submitting the next one.
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