From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E42C52E65D; Fri, 19 Dec 2025 10:55:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766141725; cv=none; b=Tz33fvHJwK0Uz8vkwqbbDK9b1MDuhoh4D9JZitqGfMsqytLY+z/uEFs2XA4dK4I4CVzWktBI1fgRPX1EaBUpO+yYSNM4zLI/3+xWLFDOV9z8774a9ESb/SDVXJ7WDcSXUbuBM8srwi3VdfHsh8pYn989I5diZBSMzkvEXijLuvI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766141725; c=relaxed/simple; bh=o0HOu8uVSlraU78h5JWalvs/oCNgESq4fsxORrizVOQ=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ta5dSWdEF0fExYMeQLrN1VyyRRqsKupNVdm1Jya3ppOoBKuuiVXEt8iS/8GHiFmbVmb5xo5KMQDsJk63zHXFNzDvjFyJtCg9Yj1dH7Rmdlr+JMyp4WK8VoakVSmZCaIN1TWPjZcsR7gZaplL1660MAuH9VLGJe4RhjvPqiYpGio= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.18.224.83]) by frasgout.his.huawei.com (SkyGuard) with ESMTPS id 4dXkvC727FzJ46l5; Fri, 19 Dec 2025 18:54:47 +0800 (CST) Received: from dubpeml100005.china.huawei.com (unknown [7.214.146.113]) by mail.maildlp.com (Postfix) with ESMTPS id 76C3B40569; Fri, 19 Dec 2025 18:55:20 +0800 (CST) Received: from localhost (10.203.177.15) by dubpeml100005.china.huawei.com (7.214.146.113) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.36; Fri, 19 Dec 2025 10:55:19 +0000 Date: Fri, 19 Dec 2025 10:55:18 +0000 From: Jonathan Cameron To: Gregory Price CC: , , , , , , , , , , Subject: Re: [PATCH v2] Documentation/driver-api/cxl: device hotplug section Message-ID: <20251219105518.00005ca6@huawei.com> In-Reply-To: <20251218170747.1278327-1-gourry@gourry.net> References: <20251218170747.1278327-1-gourry@gourry.net> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: lhrpeml500012.china.huawei.com (7.191.174.4) To dubpeml100005.china.huawei.com (7.214.146.113) On Thu, 18 Dec 2025 12:07:47 -0500 Gregory Price wrote: > Describe cxl memory device hotplug implications, in particular how the > platform CEDT CFMWS must be described to support successful hot-add of > memory devices. > > Signed-off-by: Gregory Price > --- > v2: Jonathan's clarifications and diagrams. One request for a reference given I'm not sure the whole multi-endpoint memory device thing is going to hang around so that might confuse people reading this in future - particularly as it isn't something the spec mentions. With something added there (or a statement that there isn't anything public that will do the job) Reviewed-by: Jonathan Cameron > diff --git a/Documentation/driver-api/cxl/platform/device-hotplug.rst b/Documentation/driver-api/cxl/platform/device-hotplug.rst > new file mode 100644 > index 000000000000..617e340bd556 > --- /dev/null > +++ b/Documentation/driver-api/cxl/platform/device-hotplug.rst > + > +Multi-Endpoint Memory Device Present at Boot > +-------------------------------------------- > +A hot-plug capable CXL memory device, such as one which presents multiple > +expanders as a single large-capacity device, should report the maximum > +*possible* capacity for the device at boot. :: > + > + HB0 > + RP0 > + | > + [Multi-Endpoint Memory Device] So this is the weird switch as end point thing? Maybe a reference. My guess is these will go away as switch and memory device vendors catch up with the spec, but maybe I'm wrong. > + _____|_____ > + | | > + [Endpoint0] [Empty] > + > + > +Limiting the size to the capacity preset at boot will limit hot-add support > +to replacing capacity that was present at boot.