Re: [PATCH v11 2/3] rust: add dma coherent allocator abstraction.

[Abdiel Janulgue]

On 17/02/2025 15:52, Robin Murphy wrote:
> On 15/02/2025 9:40 pm, Daniel Almeida wrote:
> > Hi Abdiel
> >
> > I noticed that there’s no API to call `dma_set_mask/ 
> > dma_set_coherent_mask`.
> >
> > This should probably be included, i.e.:
> >
> > ```
> > By default, the kernel assumes that your device can address 32-bits of 
> > DMA addressing.
> > For a 64-bit capable device, this needs to be increased, and for a 
> > device with limitations,
> > it needs to be decreased.
> > ```
>
> Oh, good point (and I'm rather ashamed I missed that!)


Ok. Missed this part while working on the nova stub and hadn't had to 
use this interface yet, but yes will add this for the next revision.

> FWIW we've been wanting to steer away from relying on the default mask 
> in new code, so it would be quite neat to actually enforce that 
> allocations fail if dma_coherent_mask hasn't been explicitly set 
> (assuming it's sufficiently cheap to keep a flag in the Device handle or 
> something like that - it's not the end of the world if it isn't practical).
Thanks for the heads-up on what this interface is expected to look like!


Regards,
Abdiel