From: "Philippe Mathieu-Daudé" <philmd@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>,
qemu-devel@nongnu.org, Thomas Huth <thuth@redhat.com>
Cc: qemu-stable@nongnu.org, "Bohdan Kostiv" <bogdan.kostiv@gmail.com>,
"Markus Armbruster" <armbru@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>
Subject: Re: [PATCH 2/2] qemu-options.hx: Improve -serial option documentation
Date: Mon, 22 Jan 2024 18:46:32 +0100 [thread overview]
Message-ID: <ceb451fd-c7c6-4ddd-861f-df8e4d897dc5@linaro.org> (raw)
In-Reply-To: <20240122163607.459769-3-peter.maydell@linaro.org>
Hi,
On 22/1/24 17:36, Peter Maydell wrote:
> 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.
Should we deprecate this broken case, suggesting to use ``null``
instead?
> 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``
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
next prev parent reply other threads:[~2024-01-22 17:47 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 ` [PATCH 2/2] qemu-options.hx: Improve -serial option documentation Peter Maydell
2024-01-22 16:41 ` Daniel P. Berrangé
2024-01-22 17:46 ` Philippe Mathieu-Daudé [this message]
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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