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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2026-09-25 15:55:03 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2026-09-25 15:55:03 -0700 |
| commit | 75467f60a3d14f08f86f2b353298d2826382ff23 (patch) | |
| tree | acd8a7d5b5a675042449386efa5b42ec44d8bf81 /Documentation/driver-api/i2c.rst | |
| download | linux-stable-75467f60a3d14f08f86f2b353298d2826382ff23.tar.gz linux-stable-75467f60a3d14f08f86f2b353298d2826382ff23.zip | |
Merge tag 'ipe-pr-20260925' of git://git.kernel.org/pub/scm/linux/kernel/git/wufan/ipegrafted
Pull IPE fixes from Fan Wu:
"Two fixes for use-after-free issues found by recent LLM-assisted code
analysis.
- move successful policy load auditing under the new policy
directory's inode lock, preventing a concurrent policy deletion
from freeing the policy while it is still being audited
- protect the dm-verity root hash with RCU, preventing policy
evaluation from racing with root hash replacement during preresume"
* tag 'ipe-pr-20260925' of git://git.kernel.org/pub/scm/linux/kernel/git/wufan/ipe:
ipe: protect the dm-verity root hash with RCU
ipe: fix use-after-free when auditing a newly loaded policy
Diffstat (limited to 'Documentation/driver-api/i2c.rst')
| -rw-r--r-- | Documentation/driver-api/i2c.rst | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/Documentation/driver-api/i2c.rst b/Documentation/driver-api/i2c.rst new file mode 100644 index 000000000..7582c079d --- /dev/null +++ b/Documentation/driver-api/i2c.rst @@ -0,0 +1,48 @@ +I\ :sup:`2`\ C and SMBus Subsystem +================================== + +I\ :sup:`2`\ C (or without fancy typography, "I2C") is an acronym for +the "Inter-IC" bus, a simple bus protocol which is widely used where low +data rate communications suffice. Since it's also a licensed trademark, +some vendors use another name (such as "Two-Wire Interface", TWI) for +the same bus. I2C only needs two signals (SCL for clock, SDA for data), +conserving board real estate and minimizing signal quality issues. Most +I2C devices use seven bit addresses, and bus speeds of up to 400 kHz; +there's a high speed extension (3.4 MHz) that's not yet found wide use. +I2C is a multi-master bus; open drain signaling is used to arbitrate +between masters, as well as to handshake and to synchronize clocks from +slower clients. + +The Linux I2C programming interfaces support the master side of bus +interactions and the slave side. The programming interface is +structured around two kinds of driver, and two kinds of device. An I2C +"Adapter Driver" abstracts the controller hardware; it binds to a +physical device (perhaps a PCI device or platform_device) and exposes a +:c:type:`struct i2c_adapter <i2c_adapter>` representing each +I2C bus segment it manages. On each I2C bus segment will be I2C devices +represented by a :c:type:`struct i2c_client <i2c_client>`. +Those devices will be bound to a :c:type:`struct i2c_driver +<i2c_driver>`, which should follow the standard Linux driver model. There +are functions to perform various I2C protocol operations; at this writing +all such functions are usable only from task context. + +The System Management Bus (SMBus) is a sibling protocol. Most SMBus +systems are also I2C conformant. The electrical constraints are tighter +for SMBus, and it standardizes particular protocol messages and idioms. +Controllers that support I2C can also support most SMBus operations, but +SMBus controllers don't support all the protocol options that an I2C +controller will. There are functions to perform various SMBus protocol +operations, either using I2C primitives or by issuing SMBus commands to +i2c_adapter devices which don't support those I2C operations. + +.. kernel-doc:: include/linux/i2c.h + :internal: + +.. kernel-doc:: drivers/i2c/i2c-boardinfo.c + :functions: i2c_register_board_info + +.. kernel-doc:: drivers/i2c/i2c-core-base.c + :export: + +.. kernel-doc:: drivers/i2c/i2c-core-smbus.c + :export: |
