Hi,

On Thu, Jan 30, 2025 at 01:08:58PM +0000, Florent Tomasin wrote:

This patch introduces a cma-heap probe function, allowing
users to register custom cma heaps in the device tree.

A "memory-region" is bound to the cma heap at probe time
allowing allocation of DMA buffers from that heap.

Use cases:
- registration of carved out secure heaps. Some devices
  are implementing secure memory by reserving a specific
  memory regions for that purpose. For example, this is the
  case of platforms making use of early version of
  ARM TrustZone.

In such a case, the CMA heap would de-facto become un-mappable for
userspace, right?

- registration of multiple memory regions at different
  locations for efficiency or HW integration reasons.
  For example, a peripheral may expect to share data at a
  specific location in RAM. This information could have been
  programmed by a FW prior to the kernel boot.

How would you differentiate between them?

Maxime