Add I2C-style new_device/delete_device sysfs attributes to SPI host
controllers, allowing userspace to instantiate and remove SPI devices
at runtime without device-tree changes.
Patch 1 adds the new_device/delete_device attributes and the supporting
infrastructure (userspace_clients list, locking, dead flag).
Patch 2 adds the ABI and user-facing documentation.
Changes since v5:
- Rebased on next-20260707 (v7.2-rc2); applies cleanly.
- Added missing kernel-doc entries for the new struct fields
(@userspace_node, @userspace_clients, @userspace_clients_lock,
@dead).
- new_device_store(): reject chip_select > U8_MAX to avoid silent
truncation in spi_set_chipselect(); parse with %u instead of %hu.
- new_device_store(): reject mode bits outside SPI_MODE_USER_MASK
(mirrors spidev's SPI_IOC_WR_MODE32 filter).
- new_device_store(): drop the unused 'n' / '%n' from sscanf().
- Minor comment cleanup.
Changes since v4:
- Removed spi_unregister_device() call from new_device_store()'s
ctlr->dead teardown path; it raced with
device_for_each_child(__unregister) in spi_unregister_controller().
Changes since v3:
- Replaced holding add_lock across __spi_add_device() + list
insertion (which caused an ABBA deadlock with kernfs) by a
ctlr->dead flag checked under add_lock / userspace_clients_lock.
- Used a compile-time #if IS_ENABLED() guard for the ctlr->dead
check in __spi_add_device(), since the dead field is conditional.
Changes since v2:
- Gated sysfs attributes and locking on CONFIG_SPI_DYNAMIC.
Changes since v1:
- Added locking to prevent races between new_device_store() and
concurrent spi_unregister_controller().
Link: https://lore.kernel.org/linux-spi/20260517201602.498135-1-va@nvidia.com/ # v5
Link: https://lore.kernel.org/linux-tegra/909f0c92-d110-4253-903e-5c81e21e12c9@nvidia.com/
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 | 238 +++++++++++++++++-
include/linux/spi/spi.h | 21 ++
5 files changed, 376 insertions(+), 6 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-class-spi-master
create mode 100644 Documentation/spi/instantiating-devices.rst
base-commit: be5c93fa674f0fc3c8f359c2143abce6bbb422e6
--
2.17.1