It's been another year of discussing the object life-time problems at conferences. I2C is one of the offenders and its problems are more complex than those of some other subsystems. It seems the revocable[1] API may make its way into the kernel this year but even with it in place, I2C won't be able to use it as there's currently nothing to *revoke*. The struct device is embedded within the i2c_adapter struct whose lifetime is tied to the provider device being bound to its driver.
Fixing this won't be fast and easy but nothing's going to happen if we don't start chipping away at it. The ultimate goal in order to be able to use an SRCU-based solution (revocable or otherwise) is to convert the embedded struct device in struct i2c_adapter into an __rcu pointer that can be *revoked*. To that end we need to hide all dereferences of adap->dev in drivers. This series addresses the usage of adap->dev in device printk() helpers (dev_err() et al). It introduces a set of i2c-specific helpers and starts using them across bus drivers. For now just 12 patches but I'll keep on doing it if these get accepted. Once these get upstream for v6.20/7.0, we'll be able to also start converting i2c drivers outside of drivers/i2c/. [1] https://lore.kernel.org/all/[email protected]/ Signed-off-by: Bartosz Golaszewski <[email protected]> --- Bartosz Golaszewski (12): i2c: add i2c_adapter-specific printk helpers i2c: sun6i-p2wi: use i2c_adapter-specific printk helpers i2c: mlxbf: use i2c_adapter-specific printk helpers i2c: isch: use i2c_adapter-specific printk helpers i2c: ali1535: use i2c_adapter-specific printk helpers i2c: scmi: use i2c_adapter-specific printk helpers i2c: ali15x3: use i2c_adapter-specific printk helpers i2c: powermac: use i2c_adapter-specific printk helpers i2c: owl: use i2c_adapter-specific printk helpers i2c: nforce2: use i2c_adapter-specific printk helpers i2c: amd756: use i2c_adapter-specific printk helpers i2c: piix4: use i2c_adapter-specific printk helpers drivers/i2c/busses/i2c-ali1535.c | 20 ++++++++++---------- drivers/i2c/busses/i2c-ali15x3.c | 20 ++++++++++---------- drivers/i2c/busses/i2c-amd756.c | 24 ++++++++++++------------ drivers/i2c/busses/i2c-isch.c | 32 ++++++++++++++++---------------- drivers/i2c/busses/i2c-mlxbf.c | 19 +++++++++---------- drivers/i2c/busses/i2c-nforce2.c | 14 +++++++------- drivers/i2c/busses/i2c-owl.c | 4 ++-- drivers/i2c/busses/i2c-piix4.c | 8 ++++---- drivers/i2c/busses/i2c-powermac.c | 26 +++++++++++++------------- drivers/i2c/busses/i2c-scmi.c | 6 +++--- drivers/i2c/busses/i2c-sun6i-p2wi.c | 8 ++++---- include/linux/i2c.h | 6 ++++++ 12 files changed, 96 insertions(+), 91 deletions(-) --- base-commit: cc3aa43b44bdb43dfbac0fcb51c56594a11338a8 change-id: 20251222-i2c-printk-helpers-a69f4403ca70 Best regards, -- Bartosz Golaszewski <[email protected]>
