linux-kernel - Re: [PATCH v3 0/5] rust: miscdevice: Provide sample driver using the new MiscDevice bindings

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Message-ID: <2024120622-unvalued-wriggle-7942@gregkh>
Date: Fri, 6 Dec 2024 09:11:30 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Lee Jones <lee@...nel.org>
Cc: linux-kernel@...r.kernel.org, arnd@...db.de, ojeda@...nel.org,
	alex.gaynor@...il.com, boqun.feng@...il.com, gary@...yguo.net,
	bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
	a.hindborg@...nel.org, aliceryhl@...gle.com, tmgross@...ch.edu,
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v3 0/5] rust: miscdevice: Provide sample driver using the
 new MiscDevice bindings

On Fri, Dec 06, 2024 at 07:44:43AM +0000, Lee Jones wrote:
> On Fri, 06 Dec 2024, Greg KH wrote:
> 
> > On Thu, Dec 05, 2024 at 04:25:17PM +0000, Lee Jones wrote:
> > > It has been suggested that the driver should use dev_info() instead of
> > > pr_info() however there is currently no scaffolding to successfully pull
> > > a 'struct device' out from driver data post register().  This is being
> > > worked on and we will convert this over in due course.
> > 
> > But the miscdevice.rs change provides this to you, right?  Or if not,
> > why not?
> 
> This does allow us to pull the 'struct device *` out from `struct
> miscdevice`; however, since this resides in MiscDeviceRegistration,
> which we lose access to after .init, we have no means to call it.
> 
> Alice is going to work on a way to use ThisModule to get the
> MiscDeviceRegistration reference back from anywhere in the module. Until
> that piece lands, we can't call MiscDeviceRegistration::device() outside
> of RustMiscDeviceModule.

That seems crazy, as ThisModule shouldn't be dealing with a static misc
device, what happens for dynamically created ones like all
normal/sane/non-example drivers do?  This should "just" be a dynamic
object that is NOT tied to the module object, or worst case, a "static"
structure that is tied to the module I guess?

Anyway, I'll let you all work it out, good luck!

greg k-h