Re: [Qemu-devel] [PATCH] char: drop data written to a disconnected pty

["Marc-André Lureau" <mlureau@redhat.com>]

Hi

----- Original Message -----
> When a serial port writes data to a pty that's disconnected, drop the
> data and return the length dropped. This avoids triggering pointless
> retries in callers like the 16550A serial_xmit(), and causes
> qemu_chr_fe_write() to write all data to the log file, rather than
> logging only while a pty client like virsh console happens to be
> connected.
> 
> Signed-off-by: Ed Swierk <eswierk@skyportsystems.com>
> ---
>  qemu-char.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/qemu-char.c b/qemu-char.c
> index 676944a..ccb6923 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -1528,7 +1528,7 @@ static int pty_chr_write(CharDriverState *chr, const
> uint8_t *buf, int len)
>          /* guest sends data, check for (re-)connect */
>          pty_chr_update_read_handler_locked(chr);
>          if (!s->connected) {
> -            return 0;
> +            return len;

I think this can be confusing if some backends silently drop the data (under disconnected state), while other don't. Perhaps we should have instead a new common chardev property "hup-drop" ? (suggestions for better name welcome)

>          }
>      }
>      return io_channel_send(s->ioc, buf, len);
> --
> 1.9.1
> 
>