Re: VIRTIO iface in mtd

[Boris Brezillon <bbrezillon@xxxxxxxxxx>]

+Richard and Miquel

Hi Marcin,

On Thu, 17 Jan 2019 21:16:19 +0100
Marcin Krzemiński <mar.krzeminski@xxxxxxxxx> wrote:

> Hello,
> 
> recently I have spoken with Boris regarding new MTD driver
> that will use VIRTIO interface to communicate with Qemu.
> To specify how should this look like exactly I am bringing the topic
> on ML.

Thanks for starting this discussion.

> My understanding is that this driver will use VIRTIO to communicate
> with Qemu. From Qemu side at the end there will be a file that will
> simulate NAND/NOR. Is it correct?

That's my understanding, but I'm not really a virtio or qemu expert so
I might be wrong.

> What use cases do you have in mind for this?

I have one in mind: simulate NAND (in particular MLC NAND) behavior in
a pseudo-realistic way to validate UBI/UBIFS code (or any other
FS/wear-leveling/FTL code) we might want to use on top of such devices

I'd also like to replace nandsim by this emulation approach. Indeed,
nandsim is emulating the parallel NAND protocol more than anything
else, which we don't really care about unless we need to test the raw
NAND framework (and I think there are better solutions to do that). On
the other hand, because nandsim tries to use the full raw NAND stack,
it's often hard to emulate real devices (ID-based detection does not
work for ONFI/JEDEC compatible devices). All of this makes nandsim a
poor choice when the user wants to emulate a NAND device to do
post-mortem analysis using a NAND dump.

Richard probably a few more use cases ;-).

Regards,

Boris

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