CHAN_RES_I2X
mailbox_reg_write(mb_chann, mb_chann->res[CHAN_RES_I2X].mb_head_ptr_reg, headptr_val);
tail = mailbox_get_tailptr(mb_chann, CHAN_RES_I2X);
ringbuf_size = mailbox_get_ringbuf_size(mb_chann, CHAN_RES_I2X);
start_addr = mb_chann->res[CHAN_RES_I2X].rb_start_addr;
memcpy(&mb_chann->res[CHAN_RES_I2X], i2x, sizeof(*i2x));
mb_chann->i2x_head = mailbox_get_headptr(mb_chann, CHAN_RES_I2X);