From mboxrd@z Thu Jan 1 00:00:00 1970 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 D0534CCD183 for ; Thu, 16 Oct 2025 06:22:28 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v9HMP-00050w-BX; Thu, 16 Oct 2025 02:21:13 -0400 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 1v9HMO-00050F-HF for qemu-devel@nongnu.org; Thu, 16 Oct 2025 02:21:12 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v9HMJ-0002bl-ID for qemu-devel@nongnu.org; Thu, 16 Oct 2025 02:21:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760595664; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fSQT9bVBPLd3pEaMVh+yLzvVImWKdAW71zwP45dvnXg=; b=ZvTxVmGi0ONJQTTx04c0k4D2OSKgI+PrldrEUC/r7NanXLC5b9tJsHCuDM4MKkUQUhmcG0 fcE00YHYxusZ5/t468t22Rny9bp0C7lqkxUIDz7pseShfQ4y+oayu1Wd3dYwnihcN0KGCV jKwuJ4mT+5MN+JyUo8+d2Ub9TPKBhdA= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-19-BLKQV7bAM16LV8XUNb6Dhw-1; Thu, 16 Oct 2025 02:21:00 -0400 X-MC-Unique: BLKQV7bAM16LV8XUNb6Dhw-1 X-Mimecast-MFC-AGG-ID: BLKQV7bAM16LV8XUNb6Dhw_1760595659 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DC7671800345; Thu, 16 Oct 2025 06:20:58 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.19]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 24F5D180057A; Thu, 16 Oct 2025 06:20:57 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 64D7F21E6A27; Thu, 16 Oct 2025 08:20:55 +0200 (CEST) From: Markus Armbruster To: Vladimir Sementsov-Ogievskiy Cc: marcandre.lureau@redhat.com, pbonzini@redhat.com, berrange@redhat.com, eduardo@habkost.net, qemu-devel@nongnu.org, raphael@enfabrica.net, yc-core@yandex-team.ru, d-tatianin@yandex-team.ru Subject: Re: [PATCH v4 5/7] chardev/char: introduce .init() + .connect() initialization interface In-Reply-To: <20251015212051.1156334-6-vsementsov@yandex-team.ru> (Vladimir Sementsov-Ogievskiy's message of "Thu, 16 Oct 2025 00:20:49 +0300") References: <20251015212051.1156334-1-vsementsov@yandex-team.ru> <20251015212051.1156334-6-vsementsov@yandex-team.ru> Date: Thu, 16 Oct 2025 08:20:55 +0200 Message-ID: <87qzv3v03c.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.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, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 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 Vladimir Sementsov-Ogievskiy writes: > We'll need a possibility to postpone connect step to later point in > time to implement backend-transfer migration feature for vhost-user-blk > in further commits. Let's start with new char interface for backends. > > .init() takes QAPI parameters and should parse them, called early > > .connect() should actually establish a connection, and postponed to > the point of attaching to frontend. Called at later point, either > at time of attaching frontend, either from qemu_chr_wait_connected(). s/either/or/ > > Signed-off-by: Vladimir Sementsov-Ogievskiy > Reviewed-by: Marc-Andr=C3=A9 Lureau [...] > diff --git a/include/chardev/char.h b/include/chardev/char.h > index 429852f8d9..d2e01f0f9c 100644 > --- a/include/chardev/char.h > +++ b/include/chardev/char.h > @@ -63,6 +63,7 @@ struct Chardev { > CharBackend *be; > char *label; > char *filename; > + bool connect_postponed; > int logfd; > int be_open; > /* used to coordinate the chardev-change special-case: */ > @@ -225,6 +226,7 @@ QemuOpts *qemu_chr_parse_compat(const char *label, co= nst char *filename, > bool permit_mux_mon); > int qemu_chr_write(Chardev *s, const uint8_t *buf, int len, bool write_a= ll); > #define qemu_chr_write_all(s, buf, len) qemu_chr_write(s, buf, len, true) > +bool qemu_chr_connect(Chardev *chr, Error **errp); > int qemu_chr_wait_connected(Chardev *chr, Error **errp); >=20=20 > #define TYPE_CHARDEV "chardev" > @@ -259,7 +261,31 @@ struct ChardevClass { > /* parse command line options and populate QAPI @backend */ > void (*parse)(QemuOpts *opts, ChardevBackend *backend, Error **errp); >=20=20 > - /* called after construction, open/starts the backend */ > + /* > + * Called after construction, create the backend, mutually exclusive > + * with @open, and should be followed by @connect(). > + * Must set the Chardev's chr->filename on success. > + */ > + bool (*init)(Chardev *chr, ChardevBackend *backend, > + Error **errp); > + > + /* > + * Called after @init(), starts the backend, mutually exclusive > + * with @open. Should care to send CHR_EVENT_OPENED when connected. Would "Must send CHR_EVENT_OPENED on success" be clearer? > + */ > + bool (*connect)(Chardev *chr, Error **errp); > + > + /* > + * Called after construction, an alternative to @init + @connect > + * and should do the work for both: create and start the backend. > + * Mutual exclusive with @init and @connect. Mutually > + * > + * May not set the Chardev's chr->filename (generic code will care), > + * and may not send CHR_EVENT_OPENED when connected (@be_opened > + * should not be touched in this case, to signal the generic code > + * to care about CHR_EVENT_OPENED). If backend care about If the backend cares > + * CHR_EVENT_OPENED, it should set @be_opened to false. > + */ > void (*open)(Chardev *chr, ChardevBackend *backend, > bool *be_opened, Error **errp);