Re: [PATCH v8 6/6] rust: samples: Add debugfs sample

[Matthew Maurer]

On Tue, Jul 1, 2025 at 7:03 AM Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, Jun 27, 2025 at 11:18:29PM +0000, Matthew Maurer wrote:
> > +        // An `Arc<Mutex<usize>>` doesn't implement display, so let's give explicit instructions on
> > +        // how to print it
> > +        let file_2 = sub.fmt_file(c_str!("arc_backed"), my_arc.clone(), &|val, f| {
> > +            writeln!(f, "locked value: {:#010x}", *val.lock())
> > +        });
>
> While cute, is this really going to be the way to describe all "custom"
> debugfs function callbacks?  No other way to point to a function itself
> instead?  Look at "fun" debugfs functions like qh_lines() in
> drivers/usb/host/ehci-dbg.c that is dumping tons of data out.  Putting
> that inline here is going to be a bit ackward :)

Good news, function pointers are legal to pass in here as well
already, I can add that usage to make it clear.

>
> So can you show an example of a "traditional" debugfs file output with
> multiple lines that is dealing with a dynamically allocated device that
> is associated with the module (not the static example you showed here),
> as that's going to be the real way this is used, not with static
> variables.

Sure, do we want to:
* Finish creating the driver struct early in `init`, then call dynamic
`.create(&str)` or `.destroy(&str)` `.modify(&str)` type things on it
in `init` to show how it would work
* Actually wire up an input source to drive create/destroy/modify
dynamically (e.g. I could implement a miscdevice) - if you want this
one, do you have a preference on where I get my input signal from?

>
> thanks,
>
> greg k-h