From patchwork Wed Oct 27 22:40:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ira Weiny X-Patchwork-Id: 12588939 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22192C4332F for ; Wed, 27 Oct 2021 22:42:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0BFD260F9B for ; Wed, 27 Oct 2021 22:42:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229987AbhJ0Woc (ORCPT ); Wed, 27 Oct 2021 18:44:32 -0400 Received: from mga17.intel.com ([192.55.52.151]:50708 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229993AbhJ0Woc (ORCPT ); Wed, 27 Oct 2021 18:44:32 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10150"; a="211054957" X-IronPort-AV: E=Sophos;i="5.87,188,1631602800"; d="scan'208";a="211054957" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Oct 2021 15:40:57 -0700 X-IronPort-AV: E=Sophos;i="5.87,188,1631602800"; d="scan'208";a="447414200" Received: from iweiny-desk2.sc.intel.com (HELO localhost) ([10.3.52.147]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Oct 2021 15:40:56 -0700 From: ira.weiny@intel.com To: Dan Williams Cc: Ira Weiny , Alison Schofield , Vishal Verma , Ben Widawsky , linux-cxl@vger.kernel.org Subject: [PATCH 3/9] Documentation/auxiliary_bus: Update Auxiliary device lifespan Date: Wed, 27 Oct 2021 15:40:37 -0700 Message-Id: <20211027224043.3551125-4-ira.weiny@intel.com> X-Mailer: git-send-email 2.28.0.rc0.12.gb6a658bd00c9 In-Reply-To: <20211027224043.3551125-1-ira.weiny@intel.com> References: <20210617221620.1904031-4-ira.weiny@intel.com> <20211027224043.3551125-1-ira.weiny@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org From: Ira Weiny It was unclear when the auxiliary device objects were to be free'ed by the parent (registering) driver. Also there are some patterns like using devm_add_action_or_reset() which are helpful to mention to those using the interface to ensure they don't double free or miss freeing the auxiliary devices. Signed-off-by: Ira Weiny --- Documentation/driver-api/auxiliary_bus.rst | 32 ++++++++++++++-------- 1 file changed, 21 insertions(+), 11 deletions(-) diff --git a/Documentation/driver-api/auxiliary_bus.rst b/Documentation/driver-api/auxiliary_bus.rst index 498b9ad4b6ff..5635845313be 100644 --- a/Documentation/driver-api/auxiliary_bus.rst +++ b/Documentation/driver-api/auxiliary_bus.rst @@ -165,9 +165,15 @@ Auxiliary Device Memory Model and Lifespan ------------------------------------------ The registering driver is the entity that allocates memory for the -auxiliary_device and register it on the auxiliary bus. It is important to note +auxiliary_device and registers it on the auxiliary bus. It is important to note that, as opposed to the platform bus, the registering driver is wholly -responsible for the management for the memory used for the driver object. +responsible for the management of the memory used for the device object. + +To be clear the memory for the auxiliary_device is freed in the release() +callback defined by the registering driver. The registering driver should only +call auxiliary_device_delete() and then auxiliary_device_uninit() when it is +done with the device. The release() function is then automatically called if +and when other drivers release their reference to the devices. A parent object, defined in the shared header file, contains the auxiliary_device. It also contains a pointer to the shared object(s), which @@ -178,18 +184,22 @@ from the pointer to the auxiliary_device, that is passed during the call to the auxiliary_driver's probe function, up to the parent object, and then have access to the shared object(s). -The memory for the auxiliary_device is freed only in its release() callback -flow as defined by its registering driver. - The memory for the shared object(s) must have a lifespan equal to, or greater -than, the lifespan of the memory for the auxiliary_device. The auxiliary_driver -should only consider that this shared object is valid as long as the -auxiliary_device is still registered on the auxiliary bus. It is up to the -registering driver to manage (e.g. free or keep available) the memory for the -shared object beyond the life of the auxiliary_device. +than, the lifespan of the memory for the auxiliary_device. The +auxiliary_driver should only consider that the shared object is valid as long +as the auxiliary_device is still registered on the auxiliary bus. It is up to +the registering driver to manage (e.g. free or keep available) the memory for +the shared object beyond the life of the auxiliary_device. The registering driver must unregister all auxiliary devices before its own -driver.remove() is completed. +driver.remove() is completed. An easy way to ensure this is to use the +devm_add_action_or_reset() call to register a function against the parent device +which unregisters the auxiliary device object(s). + +Finally, any operations which operate on the auxiliary devices must continue to +function (if only to return an error) after the registering driver unregisters +the auxiliary device. + Auxiliary Drivers =================