[Sound-open-firmware] SOF: Where is the purpose of host_msg ?

[Pierre-Louis Bossart]

>>> But it seems that all the information is exchanged via the mailbox memory.
>>> So,
>>> going back to my question will host_msg be used in the future?
>>>
> Yes, this was changed as mailbox was a more architecture neutral method of IPC
> i.e. it did not depend on passing metadata via special registers.

we still have a case for Baytrail (also reported by Daniel) where the 
IPC seems to mix commands and doorbell status:

static int byt_send_msg(struct snd_sof_dev *sdev, struct snd_sof_ipc_msg 
*msg)
{
     u64 cmd = msg->header;

     /* send the message */
     sof_mailbox_write(sdev, sdev->host_box.offset, msg->msg_data,
               msg->msg_size);
     snd_sof_dsp_write64(sdev, BYT_DSP_BAR, SHIM_IPCX,
                 cmd | SHIM_BYT_IPCX_BUSY); <<< WTH?

     return 0;
}