Re: [PATCH v3 7/7] chardev: introduce DEFINE_PROP_CHR_NO_CONNECT

[Markus Armbruster <armbru@redhat.com>]

Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> writes:

> For further vhost-user-blk backend-transfer migration realization we
> want to give it (vhost-user-blk) a possibility (and responsibility) to
> decide when do connect.
>
> For incoming migration we'll need to postpone connect at least until
> early stage of migrate-incoming command, when we already know all
> migration parameters and can decide, are we going to do incoming
> backend-transfer (and get chardev fd from incoming stream), or we
> finally need to connect.
>
> With this patch, we only provide new macro, to define chardev property,
> later it will be used in vhost-user-blk instead of DEFINE_PROP_CHR.

There is no "later" in this series.

The new macro is called DEFINE_PROP_CHR_NO_CONNECT().

> Then, vhost-user-blk will call qemu_chr_connect() by hand when needed
> (for example through qemu_chr_fe_wait_connected(), which is already
> called in vhost_user_blk_realize_connect()).
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

Excuse my quick & ignorant questions...

I understand ChardevClass provides either methods init() and connect(),
or method open().

Is a ChardevClass providing open() usable with
DEFINE_PROP_CHR_NO_CONNECT()?

Is a ChardevClass providing init() and connect() usable with
DEFINE_PROP_CHR()?

Could the code do the right thing based on presence of open() vs. init()
and connect() instead of DEFINE_PROP_CHR()
vs. DEFINE_PROP_CHR_NO_CONNECT()?