[PULL,2/2] chardev: add path option for pty backend

diff --git a/qapi/char.json b/qapi/char.json
index 42eda4f98b..e045354350 100644
--- a/qapi/char.json
+++ b/qapi/char.json
@@ -444,6 +444,20 @@ 
   'base': 'ChardevCommon',
   'if': 'CONFIG_SPICE_PROTOCOL' }
 
+##
+# @ChardevPty:
+#
+# Configuration info for pty implementation.
+#
+# @path: optional path to create a symbolic link that points to the
+#     allocated PTY
+#
+# Since: 9.2
+##
+{ 'struct': 'ChardevPty',
+  'data': { '*path': 'str' },
+  'base': 'ChardevCommon' }
+
 ##
 # @ChardevBackendKind:
 #
@@ -655,6 +669,17 @@ 
 { 'struct': 'ChardevRingbufWrapper',
   'data': { 'data': 'ChardevRingbuf' } }
 
+
+##
+# @ChardevPtyWrapper:
+#
+# @data: Configuration info for pty chardevs
+#
+# Since: 9.2
+##
+{ 'struct': 'ChardevPtyWrapper',
+  'data': { 'data': 'ChardevPty' } }
+
 ##
 # @ChardevBackend:
 #
@@ -675,7 +700,7 @@ 
             'pipe': 'ChardevHostdevWrapper',
             'socket': 'ChardevSocketWrapper',
             'udp': 'ChardevUdpWrapper',
-            'pty': 'ChardevCommonWrapper',
+            'pty': 'ChardevPtyWrapper',
             'null': 'ChardevCommonWrapper',
             'mux': 'ChardevMuxWrapper',
             'msmouse': 'ChardevCommonWrapper',
diff --git a/chardev/char-pty.c b/chardev/char-pty.c
index cc2f7617fe..cbb21b76ae 100644
--- a/chardev/char-pty.c
+++ b/chardev/char-pty.c
@@ -29,6 +29,7 @@ 
 #include "qemu/sockets.h"
 #include "qemu/error-report.h"
 #include "qemu/module.h"
+#include "qemu/option.h"
 #include "qemu/qemu-print.h"
 
 #include "chardev/char-io.h"
@@ -41,6 +42,7 @@  struct PtyChardev {
 
     int connected;
     GSource *timer_src;
+    char *path;
 };
 typedef struct PtyChardev PtyChardev;
 
@@ -204,6 +206,12 @@  static void char_pty_finalize(Object *obj)
     Chardev *chr = CHARDEV(obj);
     PtyChardev *s = PTY_CHARDEV(obj);
 
+    /* unlink symlink */
+    if (s->path) {
+        unlink(s->path);
+        g_free(s->path);
+    }
+
     pty_chr_state(chr, 0);
     object_unref(OBJECT(s->ioc));
     pty_chr_timer_cancel(s);
@@ -330,6 +338,7 @@  static void char_pty_open(Chardev *chr,
     int master_fd, slave_fd;
     char pty_name[PATH_MAX];
     char *name;
+    char *path = backend->u.pty.data->path;
 
     master_fd = qemu_openpty_raw(&slave_fd, pty_name);
     if (master_fd < 0) {
@@ -354,12 +363,36 @@  static void char_pty_open(Chardev *chr,
     g_free(name);
     s->timer_src = NULL;
     *be_opened = false;
+
+    /* create symbolic link */
+    if (path) {
+        int res = symlink(pty_name, path);
+
+        if (res != 0) {
+            error_setg_errno(errp, errno, "Failed to create PTY symlink");
+        } else {
+            s->path = g_strdup(path);
+        }
+    }
+}
+
+static void char_pty_parse(QemuOpts *opts, ChardevBackend *backend,
+                           Error **errp)
+{
+    const char *path = qemu_opt_get(opts, "path");
+    ChardevPty *pty;
+
+    backend->type = CHARDEV_BACKEND_KIND_PTY;
+    pty = backend->u.pty.data = g_new0(ChardevPty, 1);
+    qemu_chr_parse_common(opts, qapi_ChardevPty_base(pty));
+    pty->path = g_strdup(path);
 }
 
 static void char_pty_class_init(ObjectClass *oc, void *data)
 {
     ChardevClass *cc = CHARDEV_CLASS(oc);
 
+    cc->parse = char_pty_parse;
     cc->open = char_pty_open;
     cc->chr_write = char_pty_chr_write;
     cc->chr_update_read_handler = pty_chr_update_read_handler;
diff --git a/chardev/char.c b/chardev/char.c
index 35623c78a3..c0cc52824b 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -428,6 +428,11 @@  QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename,
         qemu_opt_set(opts, "path", p, &error_abort);
         return opts;
     }
+    if (strstart(filename, "pty:", &p)) {
+        qemu_opt_set(opts, "backend", "pty", &error_abort);
+        qemu_opt_set(opts, "path", p, &error_abort);
+        return opts;
+    }
     if (strstart(filename, "tcp:", &p) ||
         strstart(filename, "telnet:", &p) ||
         strstart(filename, "tn3270:", &p) ||
diff --git a/qemu-options.hx b/qemu-options.hx
index 20a1ce0d43..d5afefe5b6 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3712,7 +3712,7 @@  DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
     "-chardev console,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
     "-chardev serial,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
 #else
-    "-chardev pty,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
+    "-chardev pty,id=id[,path=path][,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
     "-chardev stdio,id=id[,mux=on|off][,signal=on|off][,logfile=PATH][,logappend=on|off]\n"
 #endif
 #ifdef CONFIG_BRLAPI
@@ -3951,12 +3951,22 @@  The available backends are:
 
     ``path`` specifies the name of the serial device to open.
 
-``-chardev pty,id=id``
-    Create a new pseudo-terminal on the host and connect to it. ``pty``
-    does not take any options.
+``-chardev pty,id=id[,path=path]``
+    Create a new pseudo-terminal on the host and connect to it.
 
     ``pty`` is not available on Windows hosts.
 
+    If ``path`` is specified, QEMU will create a symbolic link at
+    that location which points to the new PTY device.
+
+    This avoids having to make QMP or HMP monitor queries to find out
+    what the new PTY device path is.
+
+    Note that while QEMU will remove the symlink when it exits
+    gracefully, it will not do so in case of crashes or on certain
+    startup errors. It is recommended that the user checks and removes
+    the symlink after QEMU terminates to account for this.
+
 ``-chardev stdio,id=id[,signal=on|off]``
     Connect to standard input and standard output of the QEMU process.
 
@@ -4314,8 +4324,19 @@  SRST
 
             vc:80Cx24C
 
-    ``pty``
-        [Linux only] Pseudo TTY (a new PTY is automatically allocated)
+    ``pty[:path]``
+        [Linux only] Pseudo TTY (a new PTY is automatically allocated).
+
+        If ``path`` is specified, QEMU will create a symbolic link at
+        that location which points to the new PTY device.
+
+        This avoids having to make QMP or HMP monitor queries to find
+        out what the new PTY device path is.
+
+        Note that while QEMU will remove the symlink when it exits
+        gracefully, it will not do so in case of crashes or on certain
+        startup errors. It is recommended that the user checks and
+        removes the symlink after QEMU terminates to account for this.
 
     ``none``
         No device is allocated. Note that for machine types which