[Qemu-devel] [PATCH] qemu-char: inheriting ptys and imporve output from -serial pty

[Lei Li <lilei@linux.vnet.ibm.com>]

When controlling a qemu instance from another program, it's
hard to know which serial port or monitor device is redirected
to which pty. With more than one device using "pty" a lot of
guesswork is involved.

$ ./x86_64-softmmu/qemu-system-x86_64 -serial pty -serial pty -monitor pty
char device redirected to /dev/pts/5
char device redirected to /dev/pts/6
char device redirected to /dev/pts/7

Although we can find out what everything else is connected to
by the "info chardev" with "-monitor stdio" in the command line,
It'd be very useful to be able to have qemu inherit pseudo-tty
file descriptors so they could just be specified on the command
line like:

$ ./x86_64-softmmu/qemu-system-x86_64 -serial pty -serial pty -monitor pty
char device compat_monitor0 redirected to /dev/pts/5
char device serial0 redirected to /dev/pts/6
char device serial1 redirected to /dev/pts/7

Referred link: https://bugs.launchpad.net/qemu/+bug/938552

Reported-by: Craig Ringer <ringerc@gmail.com>
Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 qemu-char.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index 242b799..2b0f5f4 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -981,6 +981,7 @@ static CharDriverState *qemu_chr_open_pty(QemuOpts *opts)
     CharDriverState *chr;
     PtyCharDriver *s;
     struct termios tty;
+    char *label;
     int master_fd, slave_fd, len;
 #if defined(__OpenBSD__) || defined(__DragonFly__)
     char pty_name[PATH_MAX];
@@ -1006,7 +1007,8 @@ static CharDriverState *qemu_chr_open_pty(QemuOpts *opts)
     chr->filename = g_malloc(len);
     snprintf(chr->filename, len, "pty:%s", q_ptsname(master_fd));
     qemu_opt_set(opts, "path", q_ptsname(master_fd));
-    fprintf(stderr, "char device redirected to %s\n", q_ptsname(master_fd));
+    label = g_strdup(qemu_opts_id(opts));
+    fprintf(stderr, "char device %s redirected to %s\n", label, q_ptsname(master_fd));
 
     s = g_malloc0(sizeof(PtyCharDriver));
     chr->opaque = s;
-- 
1.7.7.6