Re: [PATCH v6 2/2] rust: add dma coherent allocator abstraction.

[Abdiel Janulgue]

On 05/12/2024 15:07, Robin Murphy wrote:
> > +    pub fn alloc_coherent(
> > +        dev: &Device,
> > +        count: usize,
> > +        flags: kernel::alloc::Flags,
>
> Might it be worth adding at least a placeholder type and argument for 
> "attrs" as well, so there's less churn involved in coming back and 
> adding it later? Or is the intention to have a separate 
> dma_alloc_attrs() constructor for such users?

It certainly is possible to include attrs in the constructor using Option:
```
    pub fn alloc_coherent(
        dev: &Device,
        count: usize,
        flags: kernel::alloc::Flags,
        attrs: Option<u64>,
    ) -> Result<CoherentAllocation<T>> {

<cut>
        let ret = unsafe {
            bindings::dma_alloc_attrs(
                dev.as_raw(),
                size,
                &mut dma_handle, flags.as_raw(),
                attrs.unwrap_or(0),
            )
        };
<cut>
    }

```
So the signature of the constructor could be:

let c = CoherentAllocation::alloc_coherent(dev, 4, GFP_KERNEL, None)?;

Andreas, Miguel, Daniel, any thoughts?

Regards,
Abdiel