RE: [PATCH v3 1/3] rpmb: add Replay Protected Memory Block (RPMB) subsystem

Hi Jens,

I realized there is one thing I wonder about:

On Tue, Feb 27, 2024 at 4:31 PM Jens Wiklander jens.wiklander@linaro.org wrote:

...

+struct rpmb_frame {

•   u8     stuff[196];
  

•   u8     key_mac[32];
  

•   u8     data[256];
  

•   u8     nonce[16];
  

•   __be32 write_counter;
  

•   __be16 addr;
  

•   __be16 block_count;
  

•   __be16 result;
  

•   __be16 req_resp;
  

+} __packed;

I didn't quite get why these things are encoded big-endian?

By the spec.

As on the producer side (the eMMC backend) it seems we are anyway calling cpu_to_be* to convert them into this format.

If this is a requirement on the consumer side (such as TEE) I think the consumer should swap the bytes rather than the producer, but I guess that kind of assumes that we foresee there will be other consumers in the first place.

This is end 2 end.

Yours, Linus Walleij