virtchnl: update header and increase header clarity

We already have the SPDX header, so just leave a copyright notice with
an updated year and get rid of the boilerplate header (so 2002!).

In addition, update a couple of comments to clarify how the various
parts of the virtchannel header interaction work.

No functional changes.
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Marek Szlosek <marek.szlosek@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

include/linux/avf/virtchnl.h

 /* SPDX-License-Identifier: GPL-2.0-only */
-/*******************************************************************************
- *
- * Intel Ethernet Controller XL710 Family Linux Virtual Function Driver
- * Copyright(c) 2013 - 2014 Intel Corporation.
- *
- * Contact Information:
- * e1000-devel Mailing List <e1000-devel@lists.sourceforge.net>
- * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
- *
- ******************************************************************************/
+/* Copyright (c) 2013-2022, Intel Corporation. */
 
 #ifndef _VIRTCHNL_H_
 #define _VIRTCHNL_H_
 
 /* Description:
- * This header file describes the VF-PF communication protocol used
- * by the drivers for all devices starting from our 40G product line
+ * This header file describes the Virtual Function (VF) - Physical Function
+ * (PF) communication protocol used by the drivers for all devices starting
+ * from our 40G product line
  *
  * Admin queue buffer usage:
  * desc->opcode is always aqc_opc_send_msg_to_pf
@@ -29,8 +21,8 @@
  * have a maximum of sixteen queues for all of its VSIs.
  *
  * The PF is required to return a status code in v_retval for all messages
- * except RESET_VF, which does not require any response. The return value
- * is of status_code type, defined in the shared type.h.
+ * except RESET_VF, which does not require any response. The returned value
+ * is of virtchnl_status_code type, defined here.
  *
  * In general, VF driver initialization should roughly follow the order of
  * these opcodes. The VF driver must first validate the API version of the
@@ -323,6 +315,9 @@ VIRTCHNL_CHECK_STRUCT_LEN(40, virtchnl_rxq_info);
  * PF configures queues and returns status.
  * If the number of queues specified is greater than the number of queues
  * associated with the VSI, an error is returned and no queues are configured.
+ * NOTE: The VF is not required to configure all queues in a single request.
+ * It may send multiple messages. PF drivers must correctly handle all VF
+ * requests.
  */
 struct virtchnl_queue_pair_info {
 	/* NOTE: vsi_id and queue_id should be identical for both queues. */
@@ -360,8 +355,13 @@ struct virtchnl_vf_res_request {
  * VF uses this message to map vectors to queues.
  * The rxq_map and txq_map fields are bitmaps used to indicate which queues
  * are to be associated with the specified vector.
- * The "other" causes are always mapped to vector 0.
+ * The "other" causes are always mapped to vector 0. The VF may not request
+ * that vector 0 be used for traffic.
  * PF configures interrupt mapping and returns status.
+ * NOTE: due to hardware requirements, all active queues (both TX and RX)
+ * should be mapped to interrupts, even if the driver intends to operate
+ * only in polling mode. In this case the interrupt may be disabled, but
+ * the ITR timer will still run to trigger writebacks.
  */
 struct virtchnl_vector_map {
 	u16 vsi_id;
@@ -388,6 +388,9 @@ VIRTCHNL_CHECK_STRUCT_LEN(14, virtchnl_irq_map_info);
  * (Currently, we only support 16 queues per VF, but we make the field
  * u32 to allow for expansion.)
  * PF performs requested action and returns status.
+ * NOTE: The VF is not required to enable/disable all queues in a single
+ * request. It may send multiple messages.
+ * PF drivers must correctly handle all VF requests.
  */
 struct virtchnl_queue_select {
 	u16 vsi_id;