Re: [PATCH v2 00/13] i2c: add and start using i2c_adapter-specific printk helpers

[Johan Hovold <johan@kernel.org>]

On Fri, Feb 27, 2026 at 10:08:34AM +0100, Wolfram Sang wrote:

> > Wolfram, I noticed you merged these last night. Please think again and
> > let's discuss the end result here. There's no question that there are
> > lifetime issues in i2c, but this is not the way to solve it.
> 
> I did think again and do not see a way how the life cycle problems can
> be solved while drivers happily access the device struct of the adapter.

There's nothing special about the struct device. What matters is that
drivers don't free memory that's still in use by the core.

> Whatever the solution to the core problem is (revocable, custom SRCU,
> something else), I still think this step is needed in any case. If I am
> wrong with this opinion, please enlighten me. Pointer to some existing
> thread is OK, too. I didn't have the bandwidth to read the revocable
> mail threads.

It's not even about revocable or SRCU, that's just an implementation
detail.

It seems all that is needed is to decouple the struct i2c_adapter from
the driver data and have core manage the lifetime of the former using
the reference count of the embedded struct device.

Then you can use an rwsem, SRCU, revocable or something else to handle
devices going away while they are in use.

Johan