[Qemu-discuss] qemu arm mtd device

[Tobias Specht]

Hi qemu community,

QEMU version:          2.4.1
Virtual Platform:       arm versatilepb
Linux Kernel host:     4.7 (Fedora 23)
Linux Kernel guest:   2.6.31

I'm trying to simulate an mtd device with qemu-system-arm.
Is it possible to do this for an versatilepb machine?
I tried the option -mtdblock, but I get a warning message and no mtd
device is recognized by the guest kernel:
$ qemu-system-arm -M versatilepb -m 128 -kernel zImage-mtdblock root.img
Warning: Orphaned drive without device:
id=mtd0,file=root.img,if=mtd,bus=0,unit=0
Uncompressing Linux...........................................done,
booting the kernel.
Linux version 2.6.31 (address@hidden) (gcc version 4.3.1
(crosstool-NG-1.10.1) ) #15 Mon Nov 21 12:24:49 CET 2016
CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=00093177
CPU: VIVT data cache, VIVT instruction cache
Machine: ARM-Versatile PB
[...]

What does the warning exactly mean, is the mtd device still attached to
the guest?
Or do I miss some kernel features on the guest side?

As far as I understood, mtd devices are quite different from block
devices like an hard drive or an SD card.
Does qemu expect a special image format to simulate an mtd device, or
does it work with an QCOW image?
Unfortunately I didn't find a lot documentation about the mtd device
option on this point.
There is another request on the devel mailinglist about that topic, but
I couldn't find an answer there as well:
https://lists.nongnu.org/archive/html/qemu-devel/2012-11/msg00981.html
(But in my case, the kernel does not even recognize an mtd device.)

I would be really happy if someone could help me out.

Best regards,
Tobias