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

[Abdiel Janulgue <abdiel.janulgue@gmail.com>]

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