On Tue, Feb 3, 2026 at 8:48 AM Gary Guo <[email protected]> wrote: > > On Tue Feb 3, 2026 at 3:46 PM GMT, Matthew Maurer wrote: > > This adds support for creating a DebugFS directory which is aware that > > it is bound to a device. As a result, callbacks under that directory > > have access to a bound device which gives them efficient access to other > > Devres, ability to use dev_err! and friends, etc. > > > > Signed-off-by: Matthew Maurer <[email protected]> > > --- > > rust/kernel/debugfs.rs | 40 ++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 40 insertions(+) > > > > diff --git a/rust/kernel/debugfs.rs b/rust/kernel/debugfs.rs > > index > > d7b8014a6474698235203f2b7d8fec96f2bb43f8..ac614d693fa73929d095b669e9ba61958bec609e > > 100644 > > --- a/rust/kernel/debugfs.rs > > +++ b/rust/kernel/debugfs.rs > > @@ -11,6 +11,11 @@ > > #[cfg(CONFIG_DEBUG_FS)] > > use crate::sync::Arc; > > use crate::{ > > + device::{ > > + Bound, > > + Device, // > > + }, > > + devres::Devres, > > fmt, > > prelude::*, > > str::CStr, > > @@ -722,3 +727,38 @@ fn new(name: &CStr) -> ScopedDir<'data, 'static> { > > } > > } > > } > > + > > +impl<'a, T: 'a + Send> Devres<Scope<T>> { > > + /// Creates a new scope, which is a directory at the root of the > > debugfs filesystem, > > + /// associated with some data `T`, enclosed in a [`Devres`] for the > > provided device. > > + /// > > + /// The `init` closure is called to populate the directory with files > > and subdirectories. These > > + /// files can reference the data stored in the scope. Because it is > > stored inside a `Devres`, > > + /// the init method is granted access to a `&Device<Bound>`. > > + /// > > + /// This can be used for cheaply accessing device-protected data > > inside DebugFS methods or > > + /// accessing device-specific methods (e.g. [`dev_err!`]). > > + /// > > + /// The entire directory tree created within the scope will be removed > > when the returned > > + /// `Scope` handle is dropped. > > + pub fn dir<E: 'a, F>( > > + dev: &'a Device<Bound>, > > + data: impl PinInit<T, E> + 'a, > > + name: &'a CStr, > > + init: F, > > + ) -> impl PinInit<Self, Error> + 'a > > + where > > + F: for<'data, 'dir> FnOnce(&'data T, &'data Device<Bound>, &'dir > > ScopedDir<'data, 'dir>) > > + + 'a, > > + Error: From<E>, > > + { > > + Devres::new( > > + dev, > > + Scope::new(data, |data| { > > + let scoped = ScopedDir::new(name); > > + init(data, dev, &scoped); > > + scoped.into_entry() > > + }), > > + ) > > + } > > +} > > I think it is a big strange to have this on `Devres` (in patch v6 it has > `Devres::dir` doesn't make > too much sense). I would suggest that we domsomething like > > impl<'a, T: 'a + Send> Scope<T> { > pub fn devres_dir( > ... > ) -> impl PinInit<Devres<Self>, Error> + 'a; > } > > To me `Devres` is just a generic container type, just like `Arc` and `ARef`, > so > the assoc functions should be defined on the concrete type. > > Also: is there a reason that this needs a special API, and by > > Devres::new(device, Scope::dir(data, c"name", |data| { > // use data and device > }); > > ?
Yes - that won't work, because the function being provided to `Scope::dir` is `for<'data, 'dir> FnOnce(&'data T, &'dir ScopedDir<'data, 'dir>)` - this means that *intentionally*, if you capture any non-static-lifetime variable from outside the closure, you won't be able to use it with the methods on `ScopedDir`, because the `'data` lifetime bound should stop you. In the general case, we wouldn't want a reference with the same lifetime as `device` in that example to be usable inside the debugfs callbacks. The device of a Devres wrapped scope is a special case because we know that it will outlive it. > > Best, > Gary > >
