From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 81F9029A2 for ; Thu, 12 Mar 2026 07:35:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773300901; cv=none; b=YnT8wU374+6uGKnknkXqhSqgbsNka/CNMIKRznxQLa+rzPr047/s1F6BQEESF2hhkScDXAARiGlDMpMk/aTXDI6uszX0TO1MY4LGIlDMIGpFPPDo4WpJXuXH4S/J2r7pd62mtxru8dzHPlBjOCVhQ4MnUfgiqys8oG5eYD8pna4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773300901; c=relaxed/simple; bh=YkcUkn9LFhsuefqnRGGzr0cA1RsdFhIPYHkyh2MKTW4=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=FQjXjFj9dTzR3z0fuknhGy+v6ab5rbUPDR6GJbWdmThOXPHhFkynV9U4iyUIH4ts5NmT/eqgka8JYcxSZ0b4VNZ9x/WFHUeKwE+sVFUvZTpXOvlY3qb9LxKmfGQo48ZHeBePR/JOr4JtXSDQOdthKvdvzLWhWY1iI4Pw6xckvXU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--joonwonkang.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=kIc95o7k; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--joonwonkang.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="kIc95o7k" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-c73a4983fc0so428249a12.3 for ; Thu, 12 Mar 2026 00:35:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1773300900; x=1773905700; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=HmIsBp0Ekf6WYLknH5UKy5YiFyyFepzCyFCAhO8kJd0=; b=kIc95o7kCc24SE80u3Znt4tJ3gt/PLowu7mVwiKPooh/0D+EWptCvgqRmEDUrtgWCV QLhBQD6Flsu7+93Aj+S/QZZO0tSFeW4LkVsjr3uQV6ldgK4A1iEcPuaCMUhcEgCbkuYo q8C7aC348dwTcWsVSN5aSHRckF5+JOIFXkuTP5yXeANGDTbCAEqRNiRZdJCl+2vQ/Q7U myZTCQ8I/jn0LVtb55ddQBvPtEBj17SHYt4Xmt4EqzwyQHCHHhoYx5aAlYDSfwokxzhH IvsveD7yaqvhrHV5+JgGXerZedsj7QqsCIcKraCA5bv9fceS0KtEB/lWKaMFpHo/3mup HU/g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773300900; x=1773905700; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=HmIsBp0Ekf6WYLknH5UKy5YiFyyFepzCyFCAhO8kJd0=; b=gKaRDvF2r1uBlsUfOjN+LY+j8mPeG76axXOJrKLaiPv/Zba26zI+ktd33G8mtzVpel S/psz+71/5HygAwLH6we51v0ngc5HBuwzMSseTWS6sFjz0FjtvjL/R19vGHIBPmxoevr ajeIwxJCnNkZROjCyeolPQYk5wm7CgAy3JbhkeMJUVLkLSwVTaOAb0E/IVKcavN25daG /mAPVSXv8OKY6z+VreduXfOlq4vkw6lkNirFbNgsxYBkSCTZOp9TXES51X+Big2gx+Jt OBW4v3ly0W+Z05dMWp3w/dThz/iMcBXCP8ndhdyEm9XNBqNEAbog+a33Lsds3JEvgmDW rO4A== X-Forwarded-Encrypted: i=1; AJvYcCV/0N5UkF+wDwteMjKgps+C8WDe+GscYQF+b5Eb7kg1Idv59TT2i1Z+8aXhDnljMVl9PmyP59tZCC8oeDc=@vger.kernel.org X-Gm-Message-State: AOJu0YyGH1vg+598OlUIJSaoVVP8+Az5+i79dnZc6Gwcoc5bEs7KvnIY eAIaIXfuZWcGD8Gne0FuhUx6jK/k8pk0e4o5BLmgGtpZ4Ac3jo4lFNSL/DBeUp7U/zLYgatsjPZ 5GWMUh9V+wbhjjtf5z2zj7rCNQA== X-Received: from pgly16.prod.google.com ([2002:a63:1810:0:b0:c73:bbdd:a2ea]) (user=joonwonkang job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6300:193:b0:398:9379:d052 with SMTP id adf61e73a8af0-398c5fb2a66mr4666799637.30.1773300899618; Thu, 12 Mar 2026 00:34:59 -0700 (PDT) Date: Thu, 12 Mar 2026 07:34:57 +0000 In-Reply-To: <20260310234616.334498-1-jassisinghbrar@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260310234616.334498-1-jassisinghbrar@gmail.com> X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog Message-ID: <20260312073457.2417149-1-joonwonkang@google.com> Subject: Re: [PATCH] RFC: mailbox: Fix NULL message support in From: Joonwon Kang To: jassisinghbrar@gmail.com Cc: arnd@arndb.de, dianders@chromium.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" > The active_req field serves double duty as both the "is a TX in > flight" flag (NULL means idle) and the storage for the in-flight > message pointer. When a client sends NULL via mbox_send_message(), > active_req is set to NULL, which the framework misinterprets as > "no active request." This breaks the TX state machine by: > > - tx_tick() short-circuits on (!mssg), skipping the tx_done > callback and the tx_complete completion > - txdone_hrtimer() skips the channel entirely since active_req > is NULL, so poll-based TX-done detection never fires. > > Fix this by introducing a MBOX_NO_MSG sentinel value that means > "no active request," freeing NULL to be valid message data. The > sentinel is internal to the mailbox core and is never exposed to > controller drivers or clients. > > The only tradeoff is that 'MBOX_NO_MSG' can not be used as a message > by clients. I was surprised to find out this alternative patch while we have been waiting a few months for your response to my previous patch for this issue on https://lore.kernel.org/all/20251126045926.2413532-1-joonwonkang@google.com/. Will you handle this issue on your end? If so, could you leave the original discussion link to the commit message so that we could better track it? Also, could you reply to the original patches next time with what you have decided or at least cc the people who posted the original patches to your new patches for better collaboration? Thanks.