Hi all!

That's only a preparation for backend-transfer migration of
vhost-user-blk, and introduced DEFINE_PROP_CHR_NO_CONNECT()
is unused now.

v2 of "vhost-user-blk: live-backend local migration" is coming
soon, and will be based on this series (and will use
DEFINE_PROP_CHR_NO_CONNECT of course).

If the design gets general approval, I'll try to update other
chardev backends, to avoid supporting two different initialization
APIs in future.


Changes in v4:

02: fix commit subject
03: add r-b by Markus
05: improve comments
07: - simplify commit message
    - more safe logic in qemu_chr_fe_init_ex()


For backend-transfer migration we are going to pass
vhost-user-blk fds, including backend chardev fd to the target
in migration stream (backed by UNIX domain socket).

So, on the target, we want to know, should we call connect(),
or is it a backend-transfer migration, and we should wait for
incoming fd.

But at initialization time we can't know it: user may setup
migration parameters (enabling backend-transfer) later.

So, let's postpone chardev open/connect phase up to attaching
to frontend. At this point we can split the behavior:

If frontend is a device, which define chardev property
using DEFINE_PROP_CHR_NO_CONNECT (at least, vhost-user-blk will
behave this way soon), then do not connect(), let the device decide
when to do connect().

Otherwise (basic DEFINE_PROP_CHR, or other calls to qemu_chr_fe_init()),
do connect() at point of attaching frontend.

The series is based on
  [PATCH 0/2] remove deprecated 'reconnect' options
Based-on: <20250924133309.334631-1-vsementsov@yandex-team.ru>

Vladimir Sementsov-Ogievskiy (7):
  chardev/char-socket: simplify reconnect-ms handling
  chardev/char: split chardev_init_common() out of qemu_char_open()
  chardev/char: qemu_char_open(): add return value
  chardev/char: move filename and be_opened handling to qemu_char_open()
  chardev/char: introduce .init() + .connect() initialization interface
  chardev/char-socket: move to .init + .connect api
  chardev: introduce DEFINE_PROP_CHR_NO_CONNECT

 chardev/char-fe.c                   |  28 ++++++-
 chardev/char-socket.c               |  64 ++++++++-------
 chardev/char.c                      | 118 ++++++++++++++++++++--------
 hw/core/qdev-properties-system.c    |  26 +++++-
 include/chardev/char-fe.h           |   6 +-
 include/chardev/char-socket.h       |   1 +
 include/chardev/char.h              |  28 ++++++-
 include/hw/qdev-properties-system.h |   3 +
 tests/unit/test-char.c              |  14 ++--
 ui/dbus-chardev.c                   |  12 ++-
 10 files changed, 225 insertions(+), 75 deletions(-)

-- 
2.48.1