iohandlers: Add support for enabling/disabling individual handlers

Hi,

This patchset adds new interfaces to work with iohandlers. It adds:

int assign_fd_handlers(int fd, IOHandlerOps *ops, void *opaque)
-- Specify io handlers for an fd
int remove_fd_handlers(int fd)
-- Remove fd handlers for fd (mark ioh for deletion)
int set_read_poll_fd_action(int fd, bool enable)
-- Enable or disable the fd_read_poll fd handler
int set_read_fd_action(int fd, bool enable)
-- Enable or disable the fd_read fd handler
int set_write_fd_action(int fd, bool enable)
-- Enable or disable the fd_read fd handler

A new struct, IOHandlerOps, is added, to collect all the ops together instead of passing individual ones to functions.

The older function, qemu_set_fd_handler2(), is now a wrapper to assign_fd_handlers() and can be deprecated by converting the existing usage to assign_fd_handlers().

v2: Address comments from Gerd:
- add comments to new interfaces
- enable all specified handlers by default in assign_fd_handlers()
- Add comments for TODO items on deprecation of older interfaces.

Please apply.

Amit Shah (5):
iohandlers: Avoid code duplication
iohandlers: Introduce assign_fd_handlers() and remove_fd_handlers
iohandlers: Allow each iohandler to be enabled/disabled individually
iohandlers: Enable an iohandler only if the associated handler exists
iohandlers: Add IOHandlerOps struct

 qemu-char.h |    7 ++
 vl.c        |  197 ++++++++++++++++++++++++++++++++++++++++++++++++----------
 2 files changed, 170 insertions(+), 34 deletions(-)

1.7.3.4