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Sat, 25 Apr 2026 10:34:25 -0700 From: Vishwaroop A To: Mark Brown CC: , , "Thierry Reding" , Jonathan Hunter , Francesco Dolcini , , Subject: [PATCH v2 0/2] spi: add sysfs interface for userspace device instantiation Date: Sat, 25 Apr 2026 17:34:23 +0000 Message-ID: <20260425173425.622042-1-va@nvidia.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20260420031417.291442-1-va@nvidia.com> References: <20260420031417.291442-1-va@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF000075ED:EE_|IA1PR12MB7639:EE_ X-MS-Office365-Filtering-Correlation-Id: e86a8734-e511-4285-164e-08dea2f0ebfd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|30052699003|1800799024|376014|82310400026|18002099003|22082099003|56012099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 8XOCmGu3RWMvPxKKSVDAgiI2hGmqu9Q1zCXDSILukKYAfQd7wk/2auUfowNlosT5VOcWd1V3OehvTbqvbbI4aQRFzwaMBA48/emiffqmr4q8AastmhSpxoNdfTB8OJrXgfUqx8cHssV1X/DfQ9nmsbXDgDPZNt+G3T9agl6zh3wmpg7SwE/NQCqHTDfevCyYG13UKuScu3oFfgOoTuJbCdw1ZO+ZeJqEm4LTmJv734WP1DnMKAGnHsSgVD4Yxrmkts9jeb5zQpfmK7epN5Fi2Fj02fDR7KqQyOFeiaPbUAihLb/YTMylgPbXGLdy3nxPSTHDq9fQId5PtYoW8vNzoa2PusJ1lSp6ENMWj1MmbUStq1NeDS9O3fUa5GCL2tsqsqJnh0SKBiPL0nkHbzIRypFzsWiDY3GWQ+BFOBxPyZM/ujCxkQHvGhMhR+pSi9gV X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Apr 2026 17:34:36.6705 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: e86a8734-e511-4285-164e-08dea2f0ebfd X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1PEPF000075ED.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB7639 Development boards such as the Jetson AGX Orin expose SPI buses on expansion headers so that users can connect and interact with SPI peripherals from userspace via /dev/spidevB.C character devices. Today there is no viable upstream mechanism to create these device nodes: - The spidev driver rejects the bare "spidev" compatible string in DT, since spidev is a Linux software interface, not a hardware description. - Vendor-specific compatible strings (e.g. "nvidia,tegra-spidev") have been rejected by DT maintainers for the same reason. The I2C subsystem solved an analogous problem years ago by exposing new_device/delete_device sysfs attributes on each i2c adapter. This series adds the same interface to SPI host controllers. Patch 1 adds the core implementation: new_device and delete_device sysfs attributes under /sys/class/spi_master/spiB/, allowing userspace to dynamically instantiate and remove SPI devices at runtime. Patch 2 adds documentation: an RST guide describing usage, parameters, examples, and limitations, plus a formal ABI entry. Link: https://lore.kernel.org/linux-tegra/909f0c92-d110-4253-903e-5c81e21e12c9@nvidia.com/ Changes in v2: - Fixed race between new_device_store() and spi_unregister_controller(): replaced spi_add_device() with direct __spi_add_device() call under add_lock so that device registration and userspace_clients list insertion are atomic with respect to controller teardown. (Mark Brown) Vishwaroop A (2): spi: add new_device/delete_device sysfs interface docs: spi: add documentation for userspace device instantiation .../ABI/testing/sysfs-class-spi-master | 34 ++++ Documentation/spi/index.rst | 1 + Documentation/spi/instantiating-devices.rst | 88 ++++++++ drivers/spi/spi.c | 190 ++++++++++++++++++ include/linux/spi/spi.h | 10 + 5 files changed, 323 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-spi-master create mode 100644 Documentation/spi/instantiating-devices.rst -- 2.17.1