On Mon, Jul 20, 2020 at 04:42:26PM +0200, SZIGETVÁRI János wrote: > Hi, > > I would like to ask a few questions about the Linux USB Gadget > project, more specifically about the mass storage gadget itself. > Currently it is possible to emulate a CD reader with an iso image > file, which works okay, and has been around for some time. > My use-case would be to use a Raspberry PI Zero, to emulate an optical > drive through an iso file and boot a desktop machine with it. > Unfortunately I also noticed that there were attempts a number of > years ago to contribute support for DVD reader emulation, but > unfortunately those efforts did not get into the mainline kernel. > > To be more specific I am referring to these: > http://linuxehacking.ovh/2013/07/12/how-to-emulatore-dvd-rom-hardware-usb/ > https://lkml.org/lkml/2015/3/7/388 > > In an effort to explore the possibilities, I took Tiziano Bacocco's > patch (the first of the two) and ported it (in a trivial way) to the > current Raspberry PI kernel versions (both 4.19.118 and 5.4.44) and > compiled the kernel and modules. > The code compiled cleanly after a few minor changes, but when I tried > to use it on an 11 GB CentOS iso image, the module crashed. Where did it crash? > I would need some help and guidance to resolve any of the possible > issues, and hopefully to make DVD-ROM emulation finally a thing in the > mass storage gadget. > I can add further details later on if there will be anyone interested. I'm not familiar with the details of DVD-ROM operation. Implementing CDROM emulation involved adding support for several additional commands to the driver, and it wouldn't be surprising if DVD-ROM emulation requires more. The patch by Tiziano Bacocco adds support for some commands, but even more may be needed. Anyway, I'll be happy to help if you have specific issues to solve. Alan Stern
