From owner-freebsd-hackers@FreeBSD.ORG  Sun Jun  3 09:14:33 2012
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From: Hans Petter Selasky <hselasky@c2i.net>
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Date: Sun, 3 Jun 2012 11:13:45 +0200
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Cc: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
Subject: Re: reverse USB driver - is it possible?
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On Sunday 03 June 2012 10:25:21 Wojciech Puchar wrote:
> for SCSI/SAS/FC there is targ(4) driver allows you to become SCSI target.
> 
> is it the same possible with USB?
> i mean if i can make my laptop to simulate say USB CDROM.
> 
> Yes there are no driver line targ(4) for USB, but it is technically
> possible hardware-wise? with any USB controler or special one?

Yes, this is possible.

Have a look at:

sys/dev/usb/storage/ustorage_fs.c

Currently just implements a RAM disk. Patches are welcome.

--HPS