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Re: [Qemu-devel] [PATCH] chardev: Allow for pty path passing.


From: Marc-André Lureau
Subject: Re: [Qemu-devel] [PATCH] chardev: Allow for pty path passing.
Date: Wed, 2 Jan 2019 12:23:50 +0400

Hi

On Sat, Dec 29, 2018 at 2:34 PM Paulo Neves <address@hidden> wrote:
>
> If a user requires a virtual serial device like provided
> by the pty char device, the user needs to accept the
> returned device name. This makes the program need to
> have smarts to parse or communicate with qemu to get the
> pty device.
> With this patch the program can pass the path where
> a symlink to the pty device will be, removing the
> need for 2 way communication or smarts.

This seems reasonable. Your patch doesn't apply on master, can you rebase it?


> ---
>  chardev/char-pty.c | 38 ++++++++++++++++++++++++++++++++++++--
>  chardev/char.c     |  6 +++++-
>  qapi/char.json     |  4 ++--
>  3 files changed, 43 insertions(+), 5 deletions(-)
>
> diff --git a/chardev/char-pty.c b/chardev/char-pty.c
> index 761ae6d..b465263 100644
> --- a/chardev/char-pty.c
> +++ b/chardev/char-pty.c
> @@ -38,6 +38,7 @@
>  typedef struct {
>      Chardev parent;
>      QIOChannel *ioc;
> +    char *link_name;
>      int read_bytes;
>
>      /* Protected by the Chardev chr_write_lock.  */
> @@ -231,6 +232,11 @@ static void char_pty_finalize(Object *obj)
>      qemu_mutex_lock(&chr->chr_write_lock);
>      pty_chr_state(chr, 0);
>      object_unref(OBJECT(s->ioc));
> +
> +    if (s->link_name) {
> +        unlink(s->link_name);
> +    }
> +

I suspect a g_free(s->link_name) is missing

>      if (s->timer_tag) {
>          g_source_remove(s->timer_tag);
>          s->timer_tag = 0;
> @@ -244,8 +250,9 @@ static void char_pty_open(Chardev *chr,
>                            bool *be_opened,
>                            Error **errp)
>  {
> +    ChardevHostdev *opts = backend->u.pty.data;
>      PtyChardev *s;
> -    int master_fd, slave_fd;
> +    int master_fd, slave_fd, symlink_ret;
>      char pty_name[PATH_MAX];
>      char *name;
>
> @@ -256,13 +263,23 @@ static void char_pty_open(Chardev *chr,
>      }
>
>      close(slave_fd);
> +
> +    s = PTY_CHARDEV(chr)
> +    s->link_name = opts->device;

You should g_strdup() it

> +    symlink_ret = symlink(pty_name, s->link_name);
> +
> +    if (symlink_ret < 0) {
> +        close(master_fd);
> +        error_setg_errno(errp, errno, "Failed to create symlink to PTY");
> +        return;
> +    }
> +
>      qemu_set_nonblock(master_fd);
>
>      chr->filename = g_strdup_printf("pty:%s", pty_name);
>      error_report("char device redirected to %s (label %s)",
>                   pty_name, chr->label);
>
> -    s = PTY_CHARDEV(chr);
>      s->ioc = QIO_CHANNEL(qio_channel_file_new_fd(master_fd));
>      name = g_strdup_printf("chardev-pty-%s", chr->label);
>      qio_channel_set_name(QIO_CHANNEL(s->ioc), name);
> @@ -271,6 +288,22 @@ static void char_pty_open(Chardev *chr,
>      *be_opened = false;
>  }
>
> +static void char_pty_parse(QemuOpts *opts, ChardevBackend *backend,
> +                                Error **errp)
> +{
> +    const char *symlink_path = qemu_opt_get(opts, "path");
> +    if(symlink_path == NULL) {
> +        error_setg(errp, "chardev: pty symlink: no device path given");
> +        return;
> +
> +    }
> +    ChardevHostdev *dev;
> +
> +    backend->type = CHARDEV_BACKEND_KIND_PTY;
> +    dev = backend->u.pipe.data = g_new0(ChardevHostdev, 1);
> +    qemu_chr_parse_common(opts, qapi_ChardevHostdev_base(dev));
> +    dev->device = g_strdup(symlink_path);
> +}
>  static void char_pty_class_init(ObjectClass *oc, void *data)
>  {
>      ChardevClass *cc = CHARDEV_CLASS(oc);
> @@ -279,6 +312,7 @@ static void char_pty_class_init(ObjectClass *oc, void 
> *data)
>      cc->chr_write = char_pty_chr_write;
>      cc->chr_update_read_handler = pty_chr_update_read_handler;
>      cc->chr_add_watch = pty_chr_add_watch;
> +    cc->parse = char_pty_parse;
>  }
>
>  static const TypeInfo char_pty_type_info = {
> diff --git a/chardev/char.c b/chardev/char.c
> index 5d52cd5..e4c5371 100644
> --- a/chardev/char.c
> +++ b/chardev/char.c
> @@ -357,7 +357,6 @@ QemuOpts *qemu_chr_parse_compat(const char *label, const 
> char *filename)
>      }
>
>      if (strcmp(filename, "null")    == 0 ||
> -        strcmp(filename, "pty")     == 0 ||
>          strcmp(filename, "msmouse") == 0 ||
>          strcmp(filename, "wctablet") == 0 ||
>          strcmp(filename, "braille") == 0 ||
> @@ -402,6 +401,11 @@ 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/qapi/char.json b/qapi/char.json
> index 6de0f29..dae4231 100644
> --- a/qapi/char.json
> +++ b/qapi/char.json
> @@ -224,7 +224,7 @@
>  ##
>  # @ChardevHostdev:
>  #
> -# Configuration info for device and pipe chardevs.
> +# Configuration info for device, pty and pipe chardevs.
>  #
>  # @device: The name of the special file for the device,
>  #          i.e. /dev/ttyS0 on Unix or COM1: on Windows
> @@ -380,7 +380,7 @@
>                                         'pipe'   : 'ChardevHostdev',
>                                         'socket' : 'ChardevSocket',
>                                         'udp'    : 'ChardevUdp',
> -                                       'pty'    : 'ChardevCommon',
> +                                       'pty'    : 'ChardevHostdev',

Better to create a new ChardevPty instead (ChardevHostdev is for host
device, here it is not)

>                                         'null'   : 'ChardevCommon',
>                                         'mux'    : 'ChardevMux',
>                                         'msmouse': 'ChardevCommon',
> --
> 2.7.4
>
>


-- 
Marc-André Lureau



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