How DMA descriptors are managed in linux kernel

creatives

I understand a DMA engine spent descriptor in processing data.

But i don`t known how exactly the descriptor is managed.

In my understand, a couple of descriptors are located in DDR memory. And it is manged by kernel.
So when a DMA spent all of descriptors, it access DDR to update their descriptor information.

I like to known how descriptor save location address is determined in linux kernel.

Actually what i like to do is changing descriptor saving location from DDR to inside memory to speed up descriptor updating process.

Thanks