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[2001:8b0:1d0::2]) by smtp.gmail.com with ESMTPSA id e15-20020a5d530f000000b003391720fa51sm9188728wrv.60.2024.01.22.08.36.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jan 2024 08:36:10 -0800 (PST) From: Peter Maydell To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Bohdan Kostiv , Markus Armbruster , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= Subject: [PATCH 2/2] qemu-options.hx: Improve -serial option documentation Date: Mon, 22 Jan 2024 16:36:07 +0000 Message-Id: <20240122163607.459769-3-peter.maydell@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240122163607.459769-1-peter.maydell@linaro.org> References: <20240122163607.459769-1-peter.maydell@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::431; envelope-from=peter.maydell@linaro.org; helo=mail-wr1-x431.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.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 Reviewed-by: Daniel P. Berrangé Reviewed-by: Philippe Mathieu-Daudé --- 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``