From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f44.google.com (mail-vk0-f44.google.com [209.85.213.44]) by kanga.kvack.org (Postfix) with ESMTP id 0848A6B0253 for ; Mon, 17 Aug 2015 11:32:09 -0400 (EDT) Received: by vkaw128 with SMTP id w128so25474277vka.1 for ; Mon, 17 Aug 2015 08:32:08 -0700 (PDT) Received: from mail-vk0-f53.google.com (mail-vk0-f53.google.com. [209.85.213.53]) by mx.google.com with ESMTPS id j1si17440735vdb.97.2015.08.17.08.32.07 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 Aug 2015 08:32:08 -0700 (PDT) Received: by vkbf67 with SMTP id f67so55794852vkb.3 for ; Mon, 17 Aug 2015 08:32:07 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20150817150158.GB2625@lst.de> References: <20150813031253.36913.29580.stgit@otcpl-skl-sds-2.jf.intel.com> <20150813035028.36913.25267.stgit@otcpl-skl-sds-2.jf.intel.com> <20150815090635.GF21033@lst.de> <20150815155846.GA26248@lst.de> <20150817150158.GB2625@lst.de> Date: Mon, 17 Aug 2015 08:32:07 -0700 Message-ID: Subject: Re: [RFC PATCH 5/7] libnvdimm, e820: make CONFIG_X86_PMEM_LEGACY a tristate option From: Dan Williams Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Hellwig Cc: "linux-kernel@vger.kernel.org" , Boaz Harrosh , Rik van Riel , "linux-nvdimm@lists.01.org" , david , Ingo Molnar , Linux MM , Mel Gorman , Ross Zwisler , "torvalds@linux-foundation.org" On Mon, Aug 17, 2015 at 8:01 AM, Christoph Hellwig wrote: > On Sat, Aug 15, 2015 at 09:04:02AM -0700, Dan Williams wrote: >> What other layer? /sys/devices/platform/e820_pmem is that exact same >> device we had before this patch. We just have a proper driver for it >> now. > > We're adding another layer of indirection between the old e820 file > and the new module. Ok, yes, I was confused by "another layer of platform_devices". That said here are the non-unit-test related reasons for this change that I would include in a new changelog: --- We currently register a platform device for e820 type-12 memory and register a nvdimm bus beneath it. Registering the platform device triggers the device-core machinery to probe for a driver, but that search currently comes up empty. Building the nvdimm-bus registration into the e820_pmem platform device registration in this way forces libnvdimm to be built-in. Instead, convert the built-in portion of CONFIG_X86_PMEM_LEGACY to simply register a platform device and move the rest of the logic to the driver for e820_pmem, for the following reasons: 1/ Letting libnvdimm be a module allows building and testing libnvdimm.ko changes without rebooting 2/ All the normal policy around modules can be applied to e820_pmem (unbind to disable and/or blacklisting the module from loading by default) 3/ Moving the driver to a generic location and converting it to scan "iomem_resource" rather than "e820.map" means any other architecture can take advantage of this simple nvdimm resource discovery mechanism by registering a resource named "Persistent Memory (legacy)" -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org