From: Peter Maydell <peter.maydell@linaro.org>
The -serial option documentation is a bit brief about '-serial none'
and '-serial null'. In particular it's not very clear about the
difference between them, and it doesn't mention that it's up to
the machine model whether '-serial none' means "don't create the
serial port" or "don't wire the serial port up to anything".
Expand on these points.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240122163607.459769-3-peter.maydell@linaro.org
(cherry picked from commit 747bfaf3a9d2f3cd51674763dc1f7575100cd200)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/qemu-options.hx b/qemu-options.hx
index 379692da86..7f798ce47e 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3968,7 +3968,8 @@ SRST
This option can be used several times to simulate up to 4 serial
ports.
- Use ``-serial none`` to disable all serial ports.
+ You can use ``-serial none`` to suppress the creation of default
+ serial devices.
Available character devices are:
@@ -3990,10 +3991,17 @@ SRST
[Linux only] Pseudo TTY (a new PTY is automatically allocated)
``none``
- No device is allocated.
+ No device is allocated. Note that for machine types which
+ emulate systems where a serial device is always present in
+ real hardware, this may be equivalent to the ``null`` option,
+ in that the serial device is still present but all output
+ is discarded. For boards where the number of serial ports is
+ truly variable, this suppresses the creation of the device.
``null``
- void device
+ A guest will see the UART or serial device as present in the
+ machine, but all output is discarded, and there is no input.
+ Conceptually equivalent to redirecting the output to ``/dev/null``.
``chardev:id``
Use a named character device defined with the ``-chardev``
--
2.39.2