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From a0dd0fc78abcc1039af4d39a9c0eb65d838621f4 Mon Sep 17 00:00:00 2001
From: Amit Shah <amit.shah@redhat.com>
Date: Mon, 21 Mar 2011 21:41:42 +0100
Subject: [PATCH] char: Add framework for a 'write unblocked' callback

The char layer can let users know that the driver will block on further
input.  For users interested in not blocking, they can assign a function
pointer that will be called back when the driver becomes writable.  This
patch just adds the function pointers to the CharDriverState structure,
future patches will enable the nonblocking and callback functionality.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Cole Robinson <crobinso@redhat.com>
---
 qemu-char.c | 3 +++
 qemu-char.h | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/qemu-char.c b/qemu-char.c
index bd443db..b5266d1 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -211,11 +211,14 @@ void qemu_chr_add_handlers(CharDriverState *s,
     }
     s->chr_can_read = handlers->fd_can_read;
     s->chr_read = handlers->fd_read;
+    s->chr_write_unblocked = handlers->fd_write_unblocked;
     s->chr_event = handlers->fd_event;
     s->handler_opaque = opaque;
     if (s->chr_update_read_handler)
         s->chr_update_read_handler(s);
 
+    s->write_blocked = false;
+
     /* We're connecting to an already opened device, so let's make sure we
        also get the open event */
     if (s->opened) {
diff --git a/qemu-char.h b/qemu-char.h
index dfa8c2d..b5e23a4 100644
--- a/qemu-char.h
+++ b/qemu-char.h
@@ -62,6 +62,9 @@ struct CharDriverState {
     IOEventHandler *chr_event;
     IOCanReadHandler *chr_can_read;
     IOReadHandler *chr_read;
+    IOHandler *chr_write_unblocked;
+    void (*chr_enable_write_fd_handler)(struct CharDriverState *chr);
+    void (*chr_disable_write_fd_handler)(struct CharDriverState *chr);
     void *handler_opaque;
     void (*chr_close)(struct CharDriverState *chr);
     void (*chr_accept_input)(struct CharDriverState *chr);
@@ -74,6 +77,7 @@ struct CharDriverState {
     char *filename;
     int opened;
     int avail_connections;
+    bool write_blocked; /* Are we in a blocked state? */
     QTAILQ_ENTRY(CharDriverState) next;
 };