Hi! With the introduction of mux-locked I2C muxes, the concept of locking only a segment of the I2C adapter tree was added. At the time, I did not want to cause a lot of extra churn, so left most users of i2c_lock_adapter alone and aparently didn't think enough about it; they simply continued to lock the whole adapter tree. However, i2c_lock_adapter is in fact wrong for almost every caller (there are naturally exceptions) that is itself not a driver for a root adapter. What normal drivers generally want is to only lock the segment of the adapter tree that their device sits on. In fact, if a device sits behind a mux-locked I2C mux, and its driver calls i2c_lock_adapter followed by an unlocked I2C transfer, things will deadlock (since even a mux-locked I2C adapter will lock its parent at some point). If the device is not sitting behind a mux-locked I2C mux (i.e. either directly on the root adapter or behind a (chain of) parent-locked I2C muxes) the root/segment distinction is of no consequence; the root adapter is locked either way. Mux-locked I2C muxes are probably not that common, and putting any of the affected devices behind one is probably even rarer, which is why we have not seen any deadlocks. At least not that I know of... Since silently changing the semantics of i2c_lock_adapter might be quite a surprise, especially for out-of-tree users, this series instead introduces new helpers to make it easier to only lock the I2C segment, then converts drivers over and finally renames the remaining i2c_lock_adapter instances to i2c_lock_root. I suggest that Wolfram takes this series through the I2C tree and creates an immutable branch for the other subsystems. The series is based on v4.17, but I did not find any new instances in neither linus-master nor linux-next and the series still applies cleanly to linus-master for me. linux-next has removed suspend support from the i2c-tegra driver. A bit strange, I thought the I2C changes was merged for this window? Anyway, the resolution for that conflict is trivial, just remove the i2c-tegra hunk from patch 11. I do not have *any* of the affected devices, and have thus only done build tests. Cheers, Peter Peter Rosin (11): i2c: add helpers for locking the I2C segment tpm/tpm_i2c_infineon: switch to i2c_lock_segment i2c: mux: pca9541: switch to i2c_lock_segment input: rohm_bu21023: switch to i2c_lock_segment media: af9013: switch to i2c_lock_segment media: drxk_hard: switch to i2c_lock_segment media: rtl2830: switch to i2c_lock_segment media: tda1004x: switch to i2c_lock_segment media: tda18271: switch to i2c_lock_segment mfd: 88pm860x-i2c: switch to i2c_lock_segment i2c: rename i2c_lock_adapter to i2c_lock_root drivers/char/tpm/tpm_i2c_infineon.c | 8 ++++---- drivers/i2c/busses/i2c-brcmstb.c | 8 ++++---- drivers/i2c/busses/i2c-davinci.c | 4 ++-- drivers/i2c/busses/i2c-gpio.c | 12 ++++++------ drivers/i2c/busses/i2c-s3c2410.c | 4 ++-- drivers/i2c/busses/i2c-sprd.c | 8 ++++---- drivers/i2c/busses/i2c-tegra.c | 8 ++++---- drivers/i2c/i2c-core-base.c | 6 +++--- drivers/i2c/i2c-core-slave.c | 8 ++++---- drivers/i2c/i2c-core-smbus.c | 4 ++-- drivers/i2c/muxes/i2c-mux-pca9541.c | 6 +++--- drivers/iio/temperature/mlx90614.c | 4 ++-- drivers/input/touchscreen/rohm_bu21023.c | 4 ++-- drivers/media/dvb-frontends/af9013.c | 8 ++++---- drivers/media/dvb-frontends/drxk_hard.c | 4 ++-- drivers/media/dvb-frontends/rtl2830.c | 12 ++++++------ drivers/media/dvb-frontends/tda1004x.c | 6 +++--- drivers/media/tuners/tda18271-common.c | 8 ++++---- drivers/mfd/88pm860x-i2c.c | 8 ++++---- include/linux/i2c.h | 22 ++++++++++++++++++++-- 20 files changed, 85 insertions(+), 67 deletions(-) -- 2.11.0
