[IMPROVEMENT] Add IPC structs' fields documentation #1429
Description
We need to have our IPCs documented to know clearly what is the purpose/role of and possibly constraints on each of the IPC struct's fields. For example, now we have:
struct sof_ipc_comp_reply {
struct sof_ipc_reply rhdr;
uint32_t id;
uint32_t offset;
} __attribute__((packed));
This doc assumes that a programmer has in-depth code knowledge: what are offset, id? Another example:
struct sof_ipc_pipe_ready {
struct sof_ipc_cmd_hdr hdr;
uint32_t comp_id;
} __attribute__((packed));
What is the acceptable range of comp_id?