The existing API has function `i2c_xfer` that transfers one or more
messages, and it only returns a single error code if the transfer was
failed. It doesn't allow to know how many of the messages were
transferred successfully, neither how many bytes were transferred in the
message that caused the fault, and also it drops all data received from
target device before the fault. There is a comment about this in
drivers/i2c/i2c-core-base.c: "REVISIT the fault reporting model here is
weak".
This patch series implements new API function `i2c_xfer_v2` that does
the same as `i2c_xfer` but also returns detailed transfer report, including
number of messages and bytes transferred before the fault. This also allows
client to get the bytes read from the target before the fault occurred.
For user space clients, new ioctl `I2C_RDWR_V2` is introduced.
In this patchset, the introduced functionality is implemented in
`i2c-nomadik` driver. Several other improvements in this driver related
to fault handling are also included in this patchset. It has been tested
on EyeQ6H-EPM6 board.
The implementation is split up into patches:
Patch #1 Introduce callback `xfer_v2` in struct `i2c_algorithm`,
function `i2c_xfer_v2`, ioctl `I2C_RDWR_V2`, structures for I2C
transfer reporting and implement all driver-independent functionality.
Patch #2 Optimize struct layout in `i2c-nomadik`.
Patch #3 Remove automatic retransfer in `i2c-nomadik`.
Patch #4 Fix error codes returned by `xfer` callback in `i2c-nomadik`.
Patch #5 Replace `dev_err` with `dev_dbg` on I2C faults in `i2c-nomadik`.
Patch #6 Add quirks that describe some limitations of `i2c-nomadik`.
Patch #7 Add support for `xfer_v2` in `i2c-nomadik`.
Signed-off-by: Dmitry Guzman <[email protected]>
---
Dmitry Guzman (7):
i2c: add I2C_XFER_V2 - support for detailed transfer reporting
i2c: nomadik: optimize layout of struct nmk_i2c_dev
i2c: nomadik: do not try to retransmit I2C message series on errors
i2c: nomadik: return proper fault codes
i2c: nomadik: change print level for fault messages to debug
i2c: nomadik: add quirks max_len=2047 and no_zero_len_read
i2c: nomadik: add support for I2C_XFER_V2 - detailed fault reporting
Documentation/i2c/dev-interface.rst | 46 ++++++++++++++++
drivers/i2c/busses/i2c-nomadik.c | 105 ++++++++++++++++++++++++-----------
drivers/i2c/i2c-core-base.c | 107 +++++++++++++++++++++++++-----------
drivers/i2c/i2c-dev.c | 79 ++++++++++++++++++++++----
include/linux/i2c.h | 12 ++++
include/trace/events/i2c.h | 6 +-
include/uapi/linux/i2c-dev.h | 9 +++
include/uapi/linux/i2c.h | 21 +++++++
8 files changed, 306 insertions(+), 79 deletions(-)
---
base-commit: 502d801f0ab03e4f32f9a33d203154ce84887921
change-id: 20260623-i2c-fault-reporting-9236c9affc2d
Best regards,
--
Dmitry Guzman <[email protected]>
