Re: [PATCH v2 1/2] rust: Update PCI binding safety comments and add inline compiler hint

["Benno Lossin" <lossin@kernel.org>]

On Fri Jul 11, 2025 at 5:02 PM CEST, Danilo Krummrich wrote:
> On Thu Jul 10, 2025 at 10:01 AM CEST, Benno Lossin wrote:
>> On Thu Jul 10, 2025 at 4:24 AM CEST, Alistair Popple wrote:
>>> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
>>> index 8435f8132e38..5c35a66a5251 100644
>>> --- a/rust/kernel/pci.rs
>>> +++ b/rust/kernel/pci.rs
>>> @@ -371,14 +371,18 @@ fn as_raw(&self) -> *mut bindings::pci_dev {
>>>  
>>>  impl Device {
>>>      /// Returns the PCI vendor ID.
>>> +    #[inline]
>>>      pub fn vendor_id(&self) -> u16 {
>>> -        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
>>> +        // SAFETY: by its type invariant `self.as_raw` is always a valid pointer to a
>>
>> s/by its type invariant/by the type invariants of `Self`,/
>> s/always//
>>
>> Also, which invariant does this refer to? The only one that I can see
>> is:
>>
>>     /// A [`Device`] instance represents a valid `struct device` created by the C portion of the kernel.
>>
>> And this doesn't say anything about the validity of `self.as_raw()`...
>
> Hm...why not? If an instance of Self always represents a valid struct pci_dev,
> then consequently self.as_raw() can only be a valid pointer to a struct pci_dev,
> no?

While it's true, you need to look into the implementation of `as_raw`.
It could very well return a null pointer...

This is where we can use a `Guarantee` on that function. But since it's
not shorter than `.0.get()`, I would just remove it.

---
Cheers,
Benno