Re: [PATCH v5 5/8] blockdev: Add a new IF type IF_OTHER

[Markus Armbruster]

Daniel P. Berrangé <berrange@redhat.com> writes:

> On Thu, Jul 28, 2022 at 10:46:35AM +0100, Peter Maydell wrote:
>> On Wed, 27 Jul 2022 at 20:03, Kevin Wolf <kwolf@redhat.com> wrote:
>> >
>> > Am 18.07.2022 um 11:49 hat Markus Armbruster geschrieben:
>> > > An OTP device isn't really a parallel flash, and neither are eFuses.
>> > > More fast-and-lose use of IF_PFLASH may exist in the tree, and maybe of
>> > > other interface types, too.
>> > >
>> > > This patch introduces IF_OTHER.  The patch after next uses it for an
>> > > EEPROM device.
>> > >
>> > > Do we want IF_OTHER?
>> >
>> > What would the semantics even be? Any block device that doesn't pick up
>> > a different category may pick up IF_OTHER backends?
>> >
>> > It certainly feels like a strange interface to ask for "other" disk and
>> > then getting as surprise what this other thing might be. It's
>> > essentially the same as having an explicit '-device other', and I
>> > suppose most people would find that strange.
>> >
>> > > If no, I guess we get to abuse IF_PFLASH some more.
>> > >
>> > > If yes, I guess we should use IF_PFLASH only for actual parallel flash
>> > > memory going forward.  Cleaning up existing abuse of IF_PFLASH may not
>> > > be worth the trouble, though.
>> > >
>> > > Thoughts?
>> >
>> > If the existing types aren't good enough (I don't have an opinion on
>> > whether IF_PFLASH is a good match), let's add a new one. But a specific
>> > new one, not just "other".
>> 
>> I think the common thread is "this isn't what anybody actually thinks
>> of as being a 'disk', but we would like to back it with a block device
>> anyway". That can cover a fair range of possibilities...
>
> Given that, do we even want/have to use -drive for this ?    We can use
> -blockdev for the backend and reference that from any -device we want
> to create, and leave -drive out of the picture entirely

-drive is our only means to configure onboard devices.

We've talked about better means a few times, but no conclusions.  I can
dig up pointers, if you're interested.