Re: [PATCH v3 2/4] serdev: add rust private data to serdev_device

[Danilo Krummrich <dakr@kernel.org>]

On 3/20/26 6:13 PM, Markus Probst wrote:
> This is unique for a bus device.
> 
> A class device has its own Data (e. g. PwmOps), i. e. it will only be
> registered after this Data has been initialized by the driver.
> 
> The receive_buf callback on the serdev device on the other hand must
> happen on the drvdata, as there is no place to store its own Data.
> 
> The drvdata is only available at the end of the probe in Rust.

In other words, devm_serdev_device_open() relies on the driver having its
private data set before this is called, since once devm_serdev_device_open() has
been called, the driver's receive_buf() callback may be called.

So, in C it is the driver's responsibility to do things in the correct order, in
Rust we want to make sure the driver can't do it out of order in the first place.

I'm still not sure whether the current approach is the best option. For
instance, we could also solve this with a separate callback. (Wasn't this even
what you had in a previous version?)