Re: [RFC PATCH v3 1/5] rtc: add device selector for rtc_class_ops callbacks

["Danilo Krummrich" <dakr@kernel.org>]

On Sat Feb 21, 2026 at 12:16 PM CET, Alexandre Belloni wrote:
> On 21/02/2026 17:31:09+0800, Alvin Sun wrote:
>> As in platform.rs [1] and i2c.rs [2], set_drvdata is always called by
>> the bus Adapter's probe_callback, not by the device driver.
>> 
>> [1]:
>> https://elixir.bootlin.com/linux/v6.19-rc5/source/rust/kernel/platform.rs#L80
>> [2]:
>> https://elixir.bootlin.com/linux/v6.19-rc5/source/rust/kernel/i2c.rs#L160
>> 
>> In Rust the Adapter already sets drvdata on the bus device in probe. If
>> the driver also calls amba_set_drvdata() there, it overwrites that
>> pointer; on remove/shutdown the framework then gets wrong data and can
>> hit use-after-free or crashes. So only the framework must set drvdata
>> on the bus device.
>
> But this is wrong, how do you then handle the class device on
> suspend/resume or on .remove?

I think you misunderstand what Alvin is saying here. We do have bus device
private data in all drivers. It's just that drivers do not set it randomly
through dev_set_drvdata() et al. Please see [1] for details.

[1] https://lore.kernel.org/all/DGKPPQI0QE73.S8I1M5NCI2BV@kernel.org/