From 7eab128ea16406bf450e0e53d9d629c290b317d7 Mon Sep 17 00:00:00 2001

From: Amit Shah <amit.shah@redhat.com>

Date: Mon, 21 Mar 2011 22:02:47 +0100

Subject: [PATCH] char: Equip the unix/tcp backend to handle nonblocking

 writes#

Now that the infrastructure is in place to return -EAGAIN to callers,

individual char drivers can set their update_fd_handlers() function to

set or remove an fd's write handler.  This handler checks if the driver

became writable.

A generic callback routine is used for unblocking writes and letting

users of chardevs know that a driver became writable again.

Signed-off-by: Amit Shah <amit.shah@redhat.com>

---

 qemu-char.c | 34 ++++++++++++++++++++++++++++++++++

 1 file changed, 34 insertions(+)

diff --git a/qemu-char.c b/qemu-char.c

index fbb6f5f..cdc7f5c 100644

--- a/qemu-char.c

+++ b/qemu-char.c

@@ -106,6 +106,19 @@

 static QTAILQ_HEAD(CharDriverStateHead, CharDriverState) chardevs =

     QTAILQ_HEAD_INITIALIZER(chardevs);

+/*

+ * Generic routine that gets called when chardev becomes writable.

+ * Lets chardev user know it's OK to send more data.

+ */

+static void char_write_unblocked(void *opaque)

+{

+    CharDriverState *chr = opaque;

+

+    chr->write_blocked = false;

+    chr->chr_disable_write_fd_handler(chr);

+    chr->chr_write_unblocked(chr->handler_opaque);

+}

+

 void qemu_chr_be_event(CharDriverState *s, int event)

 {

     /* Keep track if the char device is open */

@@ -2493,6 +2506,25 @@ static void tcp_chr_close(CharDriverState *chr)

     qemu_chr_be_event(chr, CHR_EVENT_CLOSED);

 }

+static void tcp_enable_write_fd_handler(CharDriverState *chr)

+{

+    TCPCharDriver *s = chr->opaque;

+

+    /*

+     * This function is called only after tcp_chr_connect() is called

+     * (either in 'server' mode or client mode.  So we're sure of

+     * s->fd being initialised.

+     */

+    enable_write_fd_handler(s->fd, char_write_unblocked);

+}

+

+static void tcp_disable_write_fd_handler(CharDriverState *chr)

+{

+    TCPCharDriver *s = chr->opaque;

+

+    disable_write_fd_handler(s->fd);

+}

+

 static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)

 {

     CharDriverState *chr = NULL;

@@ -2547,6 +2579,8 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)

     chr->chr_close = tcp_chr_close;

     chr->get_msgfd = tcp_get_msgfd;

     chr->chr_add_client = tcp_chr_add_client;

+    chr->chr_enable_write_fd_handler = tcp_enable_write_fd_handler;

+    chr->chr_disable_write_fd_handler = tcp_disable_write_fd_handler;

     if (is_listen) {

         s->listen_fd = fd;

-- 

1.7.11.2