[Qemu-devel] Re: [PATCH 2/5] char: Introduce char_set/remove_fd_handlers()

[Amit Shah <amit.shah@redhat.com>]

On (Tue) Jan 11 2011 [16:54:48], Gerd Hoffmann wrote:
> On 01/11/11 16:38, Amit Shah wrote:
> >On (Tue) Jan 11 2011 [15:39:46], Gerd Hoffmann wrote:
> >>On 01/11/11 12:10, Amit Shah wrote:
> >>>Introduce a char-specific wrapper to qemu_set_fd_handler functions.
> >>>This wrapper is useful to add / remove a write handler easily.  Write
> >>>handlers are only used when the backend is blocked and cannot receive
> >>>any more input.
> >>
> >>I'd suggest to add flags to enable/disable handlers to
> >>IOHandlerRecord instead.  And helper functions to set/clear them of
> >>course.
> >>
> >>With that in place you also can move the handlers to a separate
> >>struct simliar to the new QemuChrHandlers struct from patch #1.
> >
> >I'm planning to do that later -- when more backends get involved, which
> >have multiple fds (one for in, one for out).
> 
> Moving the handlers to a separate struct is clearly a incremental
> cleanup which can follow later.  Using enable/disable flags will
> probably simplify the interfaces for the non-blocking mode and thus
> simplify the whole patch series so I think this should be done now.

Agree -- but it looks to be a big patch.  I have some initial work done,
and hence am not converting anything other than unix/tcp backends.  The
proposed interface here is local to this file, and just a couple of
callers.  No big deal to change it once this is in.

(The struct for that will look like:

struct fd_handler {
	int fd;

	IOHandler *read;
	IOHandler *write;
	IOCanReadHandler *read_poll;

	bool read_enabled, write_enabled, read_poll_enabled;

	void (*set_read_handler)(IOHandler *read_handler);
	void (*set_write_handler)(IOHandler *write_handler);
	void (*set_readpoll_handler)(IOCanReadHandler *read_poll_handler);
}

This has to be embedded in the CharDriverState for each fd for each
backend.

Also: we also want to be able to select() on all fds so that we can
detect disconnection events as they happen.  So we also need an array
somewhere.)

		Amit