From: Peter Maydell <peter.maydell@linaro.org>
To: qemu-devel@nongnu.org
Cc: qemu-stable@nongnu.org, "Bohdan Kostiv" <bogdan.kostiv@gmail.com>,
"Markus Armbruster" <armbru@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>
Subject: [PATCH 2/2] qemu-options.hx: Improve -serial option documentation
Date: Mon, 22 Jan 2024 16:36:07 +0000 [thread overview]
Message-ID: <20240122163607.459769-3-peter.maydell@linaro.org> (raw)
In-Reply-To: <20240122163607.459769-1-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>
---
qemu-options.hx | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/qemu-options.hx b/qemu-options.hx
index ced82848637..d8c3fe91de1 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4129,7 +4129,8 @@ 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:
@@ -4151,10 +4152,17 @@ 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``
--
2.34.1
next prev parent reply other threads:[~2024-01-22 16:37 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-22 16:36 [PATCH 0/2] system: Fix handling of '-serial none -serial something' Peter Maydell
2024-01-22 16:36 ` [PATCH 1/2] system/vl.c: " Peter Maydell
2024-01-22 16:42 ` Daniel P. Berrangé
2024-01-23 15:57 ` Richard Henderson
2024-01-22 16:36 ` Peter Maydell [this message]
2024-01-22 16:41 ` [PATCH 2/2] qemu-options.hx: Improve -serial option documentation Daniel P. Berrangé
2024-01-22 17:46 ` Philippe Mathieu-Daudé
2024-01-22 17:55 ` Peter Maydell
2024-02-01 13:35 ` [PATCH 0/2] system: Fix handling of '-serial none -serial something' Peter Maydell
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