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Wed, 14 Jan 2026 18:15:36 +0000 Date: Wed, 14 Jan 2026 10:15:28 -0800 From: Alison Schofield To: Gregory Price CC: , , , , , , , , Subject: Re: [PATCH v2 1/3] drivers/cxl: introduce cxl_region_driver field for cxl_region Message-ID: References: <20260113202138.3021093-1-gourry@gourry.net> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260113202138.3021093-1-gourry@gourry.net> X-ClientProxiedBy: BYAPR02CA0015.namprd02.prod.outlook.com (2603:10b6:a02:ee::28) To DS4PPF0BAC23327.namprd11.prod.outlook.com (2603:10b6:f:fc02::9) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS4PPF0BAC23327:EE_|SN7PR11MB8065:EE_ X-MS-Office365-Filtering-Correlation-Id: 17c717c3-26dc-4480-f4a7-08de5398ea30 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024|7053199007; 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> > $cat regionN/region_driver > [none,dax,pmem] > > The intent is to clarify how to to add additional drivers (sysram, > dynamic_capacity, etc) in the future, and to allow switching the > driver selection via a sysfs entry `regionN/region_driver`. Needs description in Documentation/ABI/testing/sysfs-bus-cxl I think that will help me understand the switching we expect to support. > All RAM regions will be defaulted to CXL_CONTROL_DAX. CXL_CONTROL_DAX ? > > Auto-regions will either be static sysram (BIOS-onlined) and has no > region controller associated with it - or if the SP bit was set a > DAX device will be created. This will be discovered at probe time. > > Signed-off-by: Gregory Price snip > +static ssize_t region_driver_store(struct device *dev, > + struct device_attribute *attr, > + const char *buf, size_t len) > +{ > + struct cxl_region *cxlr = to_cxl_region(dev); > + struct cxl_region_params *p = &cxlr->params; > + int rc; > + > + ACQUIRE(rwsem_write_kill, rwsem)(&cxl_rwsem.region); > + if ((rc = ACQUIRE_ERR(rwsem_write_kill, &rwsem))) > + return rc; > + > + if (p->state >= CXL_CONFIG_COMMIT) > + return -EBUSY; > + > + /* PMEM drivers cannot be changed */ > + if (cxlr->mode == CXL_PARTMODE_PMEM) > + return -EBUSY; why isn't above "if (cxlr->driver == CXL_REGION_DRIVER_PMEM)" > + > + /* NONE type is not a valid selection for manually probed regions */ > + if (sysfs_streq(buf, "dax")) > + cxlr->driver = CXL_REGION_DRIVER_DAX; > + else > + return -EINVAL; > + > + return len; > +}