Re: [Qemu-devel] hw/nand hw/onenand and read-only

[Markus Armbruster <armbru@redhat.com>]

<Juha.Riihimaki@nokia.com> writes:

> On 18.10.11 16:38 , "ext Markus Armbruster" <armbru@redhat.com> wrote:
>
>>    $ qemu-system-arm -drive if=none,file=tmp.qcow2,readonly,id=foo
>>-device nand,drive=foo -kernel /dev/null
>>    qemu: hardware error: nand_device_init: Unsupported NAND block size.
>>    [...]
>>
>>Note that I didn't bother supplying a drive with sensible size.  If I
>>did, I guess I'd get nand coupled to a read-only drive.  Easy enough for
>>you to try :)
>
> Indeed, thanks ;) While I'm at it, I'll also fix the NAND init function to
> return -1 instead of aborting. I'll send patches for hw/nand and
> hw/onenand shortly. I'll simply make them reject read-only drives however

Thanks!

> both device models already support running without a drive as well by
> using a memory buffer instead so it would also be possible to make them
> use a read-only drive in a way that initial NAND/OneNAND contents would be
> read from the drive but any changes would not be written back to the drive
> and would be lost when QEMU is killed.

Sounds like it could be useful, but it's not what I'd expect for
"readonly".

You could create a boolean device property to make memory contents
transient rather than persistent.  Then reject read-only drives only in
persistent mode, i.e. when the property is false.  Feels cleaner to me.