char: move backends' io watch tag to CharDriverState

All the backends implement an io watcher tag for callbacks.  Move it to
CharDriverState from each backend's struct to make accessing the tag from
backend-neutral functions easier.

This will be used later to cancel a callback on chardev detach from a
frontend.

CC: <qemu-stable@nongnu.org>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
diff --git a/qemu-char.c b/qemu-char.c
index 6259496..99f2b94 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -798,7 +798,6 @@
 typedef struct FDCharDriver {
     CharDriverState *chr;
     GIOChannel *fd_in, *fd_out;
-    guint fd_in_tag;
     int max_size;
     QTAILQ_ENTRY(FDCharDriver) node;
 } FDCharDriver;
@@ -830,9 +829,9 @@
     status = g_io_channel_read_chars(chan, (gchar *)buf,
                                      len, &bytes_read, NULL);
     if (status == G_IO_STATUS_EOF) {
-        if (s->fd_in_tag) {
-            io_remove_watch_poll(s->fd_in_tag);
-            s->fd_in_tag = 0;
+        if (chr->fd_in_tag) {
+            io_remove_watch_poll(chr->fd_in_tag);
+            chr->fd_in_tag = 0;
         }
         qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
         return FALSE;
@@ -863,13 +862,14 @@
 {
     FDCharDriver *s = chr->opaque;
 
-    if (s->fd_in_tag) {
-        io_remove_watch_poll(s->fd_in_tag);
-        s->fd_in_tag = 0;
+    if (chr->fd_in_tag) {
+        io_remove_watch_poll(chr->fd_in_tag);
+        chr->fd_in_tag = 0;
     }
 
     if (s->fd_in) {
-        s->fd_in_tag = io_add_watch_poll(s->fd_in, fd_chr_read_poll, fd_chr_read, chr);
+        chr->fd_in_tag = io_add_watch_poll(s->fd_in, fd_chr_read_poll,
+                                           fd_chr_read, chr);
     }
 }
 
@@ -877,9 +877,9 @@
 {
     FDCharDriver *s = chr->opaque;
 
-    if (s->fd_in_tag) {
-        io_remove_watch_poll(s->fd_in_tag);
-        s->fd_in_tag = 0;
+    if (chr->fd_in_tag) {
+        io_remove_watch_poll(chr->fd_in_tag);
+        chr->fd_in_tag = 0;
     }
 
     if (s->fd_in) {
@@ -1012,7 +1012,6 @@
 
 typedef struct {
     GIOChannel *fd;
-    guint fd_tag;
     int connected;
     int read_bytes;
     guint timer_tag;
@@ -1127,9 +1126,9 @@
     PtyCharDriver *s = chr->opaque;
 
     if (!connected) {
-        if (s->fd_tag) {
-            io_remove_watch_poll(s->fd_tag);
-            s->fd_tag = 0;
+        if (chr->fd_in_tag) {
+            io_remove_watch_poll(chr->fd_in_tag);
+            chr->fd_in_tag = 0;
         }
         s->connected = 0;
         /* (re-)connect poll interval for idle guests: once per second.
@@ -1144,7 +1143,8 @@
         if (!s->connected) {
             s->connected = 1;
             qemu_chr_be_generic_open(chr);
-            s->fd_tag = io_add_watch_poll(s->fd, pty_chr_read_poll, pty_chr_read, chr);
+            chr->fd_in_tag = io_add_watch_poll(s->fd, pty_chr_read_poll,
+                                               pty_chr_read, chr);
         }
     }
 }
@@ -1155,9 +1155,9 @@
     PtyCharDriver *s = chr->opaque;
     int fd;
 
-    if (s->fd_tag) {
-        io_remove_watch_poll(s->fd_tag);
-        s->fd_tag = 0;
+    if (chr->fd_in_tag) {
+        io_remove_watch_poll(chr->fd_in_tag);
+        chr->fd_in_tag = 0;
     }
     fd = g_io_channel_unix_get_fd(s->fd);
     g_io_channel_unref(s->fd);
@@ -2165,7 +2165,6 @@
 typedef struct {
     int fd;
     GIOChannel *chan;
-    guint tag;
     uint8_t buf[READ_BUF_LEN];
     int bufcnt;
     int bufptr;
@@ -2221,9 +2220,9 @@
     s->bufcnt = bytes_read;
     s->bufptr = s->bufcnt;
     if (status != G_IO_STATUS_NORMAL) {
-        if (s->tag) {
-            io_remove_watch_poll(s->tag);
-            s->tag = 0;
+        if (chr->fd_in_tag) {
+            io_remove_watch_poll(chr->fd_in_tag);
+            chr->fd_in_tag = 0;
         }
         return FALSE;
     }
@@ -2242,22 +2241,23 @@
 {
     NetCharDriver *s = chr->opaque;
 
-    if (s->tag) {
-        io_remove_watch_poll(s->tag);
-        s->tag = 0;
+    if (chr->fd_in_tag) {
+        io_remove_watch_poll(chr->fd_in_tag);
+        chr->fd_in_tag = 0;
     }
 
     if (s->chan) {
-        s->tag = io_add_watch_poll(s->chan, udp_chr_read_poll, udp_chr_read, chr);
+        chr->fd_in_tag = io_add_watch_poll(s->chan, udp_chr_read_poll,
+                                           udp_chr_read, chr);
     }
 }
 
 static void udp_chr_close(CharDriverState *chr)
 {
     NetCharDriver *s = chr->opaque;
-    if (s->tag) {
-        io_remove_watch_poll(s->tag);
-        s->tag = 0;
+    if (chr->fd_in_tag) {
+        io_remove_watch_poll(chr->fd_in_tag);
+        chr->fd_in_tag = 0;
     }
     if (s->chan) {
         g_io_channel_unref(s->chan);
@@ -2308,7 +2308,7 @@
 typedef struct {
 
     GIOChannel *chan, *listen_chan;
-    guint tag, listen_tag;
+    guint listen_tag;
     int fd, listen_fd;
     int connected;
     int max_size;
@@ -2493,9 +2493,9 @@
         if (s->listen_chan) {
             s->listen_tag = g_io_add_watch(s->listen_chan, G_IO_IN, tcp_chr_accept, chr);
         }
-        if (s->tag) {
-            io_remove_watch_poll(s->tag);
-            s->tag = 0;
+        if (chr->fd_in_tag) {
+            io_remove_watch_poll(chr->fd_in_tag);
+            chr->fd_in_tag = 0;
         }
         g_io_channel_unref(s->chan);
         s->chan = NULL;
@@ -2526,7 +2526,8 @@
 
     s->connected = 1;
     if (s->chan) {
-        s->tag = io_add_watch_poll(s->chan, tcp_chr_read_poll, tcp_chr_read, chr);
+        chr->fd_in_tag = io_add_watch_poll(s->chan, tcp_chr_read_poll,
+                                           tcp_chr_read, chr);
     }
     qemu_chr_be_generic_open(chr);
 }
@@ -2609,9 +2610,9 @@
 {
     TCPCharDriver *s = chr->opaque;
     if (s->fd >= 0) {
-        if (s->tag) {
-            io_remove_watch_poll(s->tag);
-            s->tag = 0;
+        if (chr->fd_in_tag) {
+            io_remove_watch_poll(chr->fd_in_tag);
+            chr->fd_in_tag = 0;
         }
         if (s->chan) {
             g_io_channel_unref(s->chan);