From patchwork Wed Feb 21 21:46:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 13566537 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 850D3C54788 for ; Wed, 21 Feb 2024 21:52:07 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rcuRI-0000w3-Qh; Wed, 21 Feb 2024 16:47:40 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rcuRG-0000sn-8Q; Wed, 21 Feb 2024 16:47:38 -0500 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rcuRE-0007Ld-EP; Wed, 21 Feb 2024 16:47:37 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 593514F862; Thu, 22 Feb 2024 00:47:46 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id F39B2869E3; Thu, 22 Feb 2024 00:47:23 +0300 (MSK) Received: (nullmailer pid 2339841 invoked by uid 1000); Wed, 21 Feb 2024 21:47:23 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Peter Maydell , =?utf-8?q?Daniel_P_=2E_Berrang=C3=A9?= , =?utf-8?q?Phi?= =?utf-8?q?lippe_Mathieu-Daud=C3=A9?= , Michael Tokarev Subject: [Stable-7.2.10 06/33] qemu-options.hx: Improve -serial option documentation Date: Thu, 22 Feb 2024 00:46:49 +0300 Message-Id: <20240221214723.2339742-6-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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 From: Peter Maydell 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 Message-id: 20240122163607.459769-3-peter.maydell@linaro.org (cherry picked from commit 747bfaf3a9d2f3cd51674763dc1f7575100cd200) Signed-off-by: Michael Tokarev 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``