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