Re: [PATCH 1/2] rust: dma: make use of start_ptr() and start_ptr_mut()

[Danilo Krummrich]

On 11/4/25 9:39 AM, Alice Ryhl wrote:
> On Mon, Nov 03, 2025 at 08:06:49PM +0100, Danilo Krummrich wrote:
>> Using start_ptr() and start_ptr_mut() has the advantage that we inherit
>> the requirements the a mutable or immutable reference from those
>> methods.
>>
>> Hence, use them instead of self.cpu_addr.
>>
>> Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
> 
>>          // and we've just checked that the range and index is within bounds.
>>          // - `offset` can't overflow since it is smaller than `self.count` and we've checked
>>          // that `self.count` won't overflow early in the constructor.
>> -        Ok(unsafe { self.cpu_addr.add(offset) })
>> +        Ok(unsafe { self.start_ptr().cast_mut().add(offset) })
> 
> I guess this shows that the mutable/immutable requirements we inherit
> aren't actually what we need?

item_from_index() is used for the dma_read!() and dma_write!() macros, hence
this one is on purpose.