Re: [PATCH v5 2/9] rust: device: Enable accessing the FwNode of a Device

["Remo Senekowitsch" <remo@buenzli.dev>]

On Wed May 21, 2025 at 1:59 PM CEST, Greg Kroah-Hartman wrote:
> On Tue, May 20, 2025 at 10:00:17PM +0200, Remo Senekowitsch wrote:
>> Subsequent patches will add methods for reading properties to FwNode.
>> The first step to accessing these methods will be to access the "root"
>> FwNode of a Device.
>> 
>> Add the method `fwnode` to `Device`.
>> 
>> Signed-off-by: Remo Senekowitsch <remo@buenzli.dev>
>> ---
>>  rust/kernel/device.rs | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>> 
>> diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
>> index d8619d4485fb4..b4b7056eb80f8 100644
>> --- a/rust/kernel/device.rs
>> +++ b/rust/kernel/device.rs
>> @@ -186,6 +186,21 @@ unsafe fn printk(&self, klevel: &[u8], msg: fmt::Arguments<'_>) {
>>          };
>>      }
>>  
>> +    /// Obtain the [`FwNode`](property::FwNode) corresponding to the device.
>> +    pub fn fwnode(&self) -> Option<&property::FwNode> {
>> +        // SAFETY: `self` is valid.
>> +        let fwnode_handle = unsafe { bindings::__dev_fwnode(self.as_raw()) };
>
> Why isn't this calling __dev_fwnode_const()?  And there's no way to just
> use dev_fwnode() directly?  Ugh, it's a macro...

I think I had that in earlier versions of the patch series. There was
a helper to call the macro from Rust. It was pointed out that this is
not clearly expressing the intent - whether fwnode is mutated or not.
And I think someone said the fwnode can be mutated so __dev_fwnode() is
semantically correct.