Ringbuffer with fixed size but variable capacity?

[romainreignier]

For an embedded project using no_std and no alloc, I would like a ring buffer but the number of elements allowed in the buffer can be changed at runtime based on a configuration value.
For now, it seems to me that ConstGenericRingBuffer need to know its capacity at compile time while an AllocRingBuffer is preferred to my use-case but I need to enable a GlobalAllocator in my application.

So something like a ConstGenericRingBuffer with a compile-time max size and a runtime capacity would cover my need, the max size would be allocated on the stack and my application have to make sure to not require a capacity greater than the size.
But is it something common enough to try to implement it?

If I really need to add an allocator for AllocRingBuffer, maybe we could implement a constructor taking an allocator as argument like Vec::new_in using the Rust allocator_api feature, as explained in the esp-alloc crate doc to avoid the GlobalAllocator and allow better control over allocations.