From 8baf60005853af814834cf23be0afc0d4ebb2f3b Mon Sep 17 00:00:00 2001
From: David Su <dysu@google.com>
Date: Wed, 31 Mar 2021 12:27:21 -0700
Subject: [PATCH] Wifi HAL Multi STA: Clarify behavior during single STA

Firmware should maintain the last set multi STA
use case & primary connection across periods of
single STA.

Bug: 183861582
Test: compiles
Change-Id: Iab7b9298216a90ddcd792aec794266c9edb397fa
---
 wifi/1.5/IWifiChip.hal | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/wifi/1.5/IWifiChip.hal b/wifi/1.5/IWifiChip.hal
index e199850c1a..8d7a36e285 100644
--- a/wifi/1.5/IWifiChip.hal
+++ b/wifi/1.5/IWifiChip.hal
@@ -47,6 +47,15 @@ interface IWifiChip extends @1.4::IWifiChip {
      *   - This will be invoked before an active wifi connection is established on the second
      *     interface.
      *   - This use-case hint is implicitly void when the second STA interface is brought down.
+     *   - When there is only 1 STA interface, the must should still retain the last use case
+     *     set, which must become active the next time multi STA is enabled.
+     *     1. Initialize with single STA.
+     *     2. Framework creates second STA.
+     *     3. Framework sets use case to DUAL_STA_NON_TRANSIENT_UNBIASED.
+     *     4. Framework destroys second STA. Only 1 STA remains.
+     *     5. Framework recreates second STA.
+     *     6. The active use case remains DUAL_STA_NON_TRANSIENT_UNBIASED (i.e. firmware should not
+     *        automatically change it during period of single STA unless requested by framework).
      */
     enum MultiStaUseCase : uint8_t {
         /**
@@ -100,11 +109,14 @@ interface IWifiChip extends @1.4::IWifiChip {
     /**
      * Invoked to indicate that the provided iface is the primary STA iface when there are more
      * than 1 STA iface concurrently active.
-     * Note: If the wifi firmware/chip cannot support multiple instances of any offload
-     * (like roaming, APF, rssi threshold, etc), the firmware should ensure that these
-     * offloads are at least enabled for the primary interface. If the new primary interface is
-     * already connected to a network, the firmware must switch all the offloads on
-     * this new interface without disconnecting.
+     * Notes:
+     * - If the wifi firmware/chip cannot support multiple instances of any offload
+     *   (like roaming, APF, rssi threshold, etc), the firmware should ensure that these
+     *   offloads are at least enabled for the primary interface. If the new primary interface is
+     *   already connected to a network, the firmware must switch all the offloads on
+     *   this new interface without disconnecting.
+     * - When there is only 1 STA interface, the firmware must still retain the last primary
+     *   connection, which must become active the next time multi STA is enabled.
      *
      * @param ifname Name of the STA iface.
      * @return status WifiStatus of the operation.