[PATCH 6/8] chardev: introduce .chr_get_pty_name() handler

[Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxxx>]

Currently we do two wrong things:

1. Abuse s->filename to get pty_name from it

2. Violate layering with help of CHARDEV_IS_PTY()

Let's get rid of both, and introduce correct way to get pty name in
generic code, if available.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxxx>
---
 chardev/char-pty.c     |  7 +++++++
 chardev/char.c         | 19 +++++++++++++------
 hw/char/xen_console.c  |  7 ++++---
 include/chardev/char.h |  7 +++++--
 4 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/chardev/char-pty.c b/chardev/char-pty.c
index a582aa7bc7..047aade09e 100644
--- a/chardev/char-pty.c
+++ b/chardev/char-pty.c
@@ -387,6 +387,12 @@ static void pty_chr_parse(QemuOpts *opts, ChardevBackend 
*backend, Error **errp)
     pty->path = g_strdup(path);
 }
 
+static char *pty_chr_get_pty_name(Chardev *chr)
+{
+    PtyChardev *s = PTY_CHARDEV(chr);
+    return g_strdup(s->pty_name);
+}
+
 static void char_pty_class_init(ObjectClass *oc, const void *data)
 {
     ChardevClass *cc = CHARDEV_CLASS(oc);
@@ -396,6 +402,7 @@ static void char_pty_class_init(ObjectClass *oc, const void 
*data)
     cc->chr_write = pty_chr_write;
     cc->chr_update_read_handler = pty_chr_update_read_handler;
     cc->chr_add_watch = pty_chr_add_watch;
+    cc->chr_get_pty_name = pty_chr_get_pty_name;
 }
 
 static const TypeInfo char_pty_type_info = {
diff --git a/chardev/char.c b/chardev/char.c
index 44bfed3627..0dc792b88f 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -1090,9 +1090,7 @@ ChardevReturn *qmp_chardev_add(const char *id, 
ChardevBackend *backend,
     }
 
     ret = g_new0(ChardevReturn, 1);
-    if (CHARDEV_IS_PTY(chr)) {
-        ret->pty = g_strdup(chr->filename + 4);
-    }
+    ret->pty = qemu_chr_get_pty_name(chr);
 
     return ret;
 
@@ -1101,6 +1099,17 @@ err:
     return NULL;
 }
 
+char *qemu_chr_get_pty_name(Chardev *chr)
+{
+    ChardevClass *cc = CHARDEV_GET_CLASS(chr);
+
+    if (cc->chr_get_pty_name) {
+        return cc->chr_get_pty_name(chr);
+    }
+
+    return NULL;
+}
+
 ChardevReturn *qmp_chardev_change(const char *id, ChardevBackend *backend,
                                   Error **errp)
 {
@@ -1192,9 +1201,7 @@ ChardevReturn *qmp_chardev_change(const char *id, 
ChardevBackend *backend,
     object_unref(OBJECT(chr_new));
 
     ret = g_new0(ChardevReturn, 1);
-    if (CHARDEV_IS_PTY(chr_new)) {
-        ret->pty = g_strdup(chr_new->filename + 4);
-    }
+    ret->pty = qemu_chr_get_pty_name(chr_new);
 
     return ret;
 }
diff --git a/hw/char/xen_console.c b/hw/char/xen_console.c
index a639fb0b11..7502de46e4 100644
--- a/hw/char/xen_console.c
+++ b/hw/char/xen_console.c
@@ -418,6 +418,7 @@ static void xen_console_realize(XenDevice *xendev, Error 
**errp)
     XenConsole *con = XEN_CONSOLE_DEVICE(xendev);
     Chardev *cs = qemu_chr_fe_get_driver(&con->chr);
     unsigned int u;
+    g_autofree char *pty_name = NULL;
 
     if (!cs) {
         error_setg(errp, "no backing character device");
@@ -450,9 +451,9 @@ static void xen_console_realize(XenDevice *xendev, Error 
**errp)
 
     trace_xen_console_realize(con->dev, object_get_typename(OBJECT(cs)));
 
-    if (CHARDEV_IS_PTY(cs)) {
-        /* Strip the leading 'pty:' */
-        xen_device_frontend_printf(xendev, "tty", "%s", cs->filename + 4);
+    pty_name = qemu_chr_get_pty_name(cs);
+    if (pty_name) {
+        xen_device_frontend_printf(xendev, "tty", "%s", pty_name);
     }
 
     /* No normal PV driver initialization for the primary console under Xen */
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 23a227dca9..d36e50b99e 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -247,8 +247,6 @@ OBJECT_DECLARE_TYPE(Chardev, ChardevClass, CHARDEV)
 
 #define CHARDEV_IS_RINGBUF(chr) \
     object_dynamic_cast(OBJECT(chr), TYPE_CHARDEV_RINGBUF)
-#define CHARDEV_IS_PTY(chr) \
-    object_dynamic_cast(OBJECT(chr), TYPE_CHARDEV_PTY)
 
 struct ChardevClass {
     ObjectClass parent_class;
@@ -306,6 +304,9 @@ struct ChardevClass {
 
     /* handle various events */
     void (*chr_be_event)(Chardev *s, QEMUChrEvent event);
+
+    /* return PTY name if available */
+    char *(*chr_get_pty_name)(Chardev *s);
 };
 
 Chardev *qemu_chardev_new(const char *id, const char *typename,
@@ -320,4 +321,6 @@ GSource *qemu_chr_timeout_add_ms(Chardev *chr, guint ms,
 void suspend_mux_open(void);
 void resume_mux_open(void);
 
+char *qemu_chr_get_pty_name(Chardev *chr);
+
 #endif
-- 
2.48.1