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Wed, 13 May 2026 05:46:00 +0000 Message-ID: <01df8e0e-9041-401b-ab73-634701c4acdc@intel.com> Date: Wed, 13 May 2026 08:45:55 +0300 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6/8] i3c: master: Defer new-device registration out of DAA caller context To: Frank Li CC: , , References: <20260512121732.406009-1-adrian.hunter@intel.com> <20260512121732.406009-7-adrian.hunter@intel.com> Content-Language: en-US From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo, Business Identity Code: 0357606 - 4, Domiciled in Helsinki In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: DB8PR06CA0053.eurprd06.prod.outlook.com (2603:10a6:10:120::27) To IA1PR11MB7198.namprd11.prod.outlook.com (2603:10b6:208:419::15) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA1PR11MB7198:EE_|SA3PR11MB8046:EE_ X-MS-Office365-Filtering-Correlation-Id: 88934645-dab0-4cd5-0d09-08deb0b2e925 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|56012099003|22082099003|18002099003|11063799003; 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As well as assigning addresses to >> any newly arrived devices, this restores the dynamic address of devices >> that lost it across system suspend, so it has to run as part of the >> controller's resume path. >> >> A side effect of i3c_master_do_daa_ext() today is that it also >> registers any newly discovered I3C devices with the driver model >> inline, via i3c_master_register_new_i3c_devs(). Doing that from the >> resume path is problematic: a hot-join-capable device may join the bus >> during this same DAA, and registering it immediately would push driver >> model work (probing, sysfs, etc.) into the controller's resume context, >> where the rest of the system is not yet fully resumed and the >> controller driver is still partway through its own resume sequence. >> >> Decouple discovery from registration: add a reg_work work item to >> struct i3c_master_controller and have i3c_master_do_daa_ext() queue it >> on master->wq (the freezable workqueue) instead of calling >> i3c_master_register_new_i3c_devs() directly. The worker performs the >> registration only when the controller is not shutting_down, and is >> cancelled alongside hj_work in i3c_master_shutdown(). Because wq is >> freezable, any newly observed devices end up being registered after >> the system has finished resuming. >> >> i3c_master_register() also routes its initial post-bus-init registration >> through reg_work, using flush_work() to keep probe-time behavior >> synchronous. This keeps a single registration code path and ensures the >> worker is the only writer of desc->dev. > > why not direct use hj_work? i3c_master_register_new_i3c_devs() use of desc->dev is racy, so i3c_master_register_new_i3c_devs() must not be allowed to race with itself. Having it only ever run via reg_work achieves that.