Re: [PATCH v3 1/5] rust: miscdevice: Provide accessor to pull out miscdevice::this_device

Lee Jones
2024-12-06T07:20:31Z

On Thu, 05 Dec 2024, Fiona Behrens wrote:

>
>
> On 5 Dec 2024, at 17:25, Lee Jones wrote:
>
> > There are situations where a pointer to a `struct device` will become
> > necessary (e.g. for calling into dev_*() functions). This accessor
> > allows callers to pull this out from the `struct miscdevice`.
> >
> > Signed-off-by: Lee Jones <lee@kernel.org>
> > ---
> > rust/kernel/miscdevice.rs | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
> > index 7e2a79b3ae26..55340f316006 100644
> > --- a/rust/kernel/miscdevice.rs
> > +++ b/rust/kernel/miscdevice.rs
> > @@ -10,11 +10,13 @@
> >
> > use crate::{
> > bindings,
> > + device::Device,
> > error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
> > prelude::*,
> > str::CStr,
> > types::{ForeignOwnable, Opaque},
> > };
> > +
> > use core::{
> > ffi::{c_int, c_long, c_uint, c_ulong},
> > marker::PhantomData,
> > @@ -84,6 +86,13 @@ pub fn register(opts: MiscDeviceOptions) -> impl PinInit<Self, Error> {
> > pub fn as_raw(&self) -> *mut bindings::miscdevice {
> > self.inner.get()
> > }
> > +
> > + /// Returns a pointer to the current Device
>
> I would not call this pointer but rather reference? Pointer is usually associated with *mut or *const, and this is a reference to the Device abstraction

No, no, my Rustacean friend. That's not the point of the comment at
all. We can all see that it the return value is literally a reference
to Device (&Device), but the thing it's actually passing back is a
`struct device *`:

% git --no-pager grep -n this_device -- include/
include/linux/miscdevice.h:85: struct device *this_device;

I'll change the comment to be a lot more intentional.

--
Lee Jones [李琼斯]