[RFC PATCH 4/4] wifi: rtw89: raise RTW89_MAX_INTERFACE_NUM to 3 for P2P-Device concurrency

Live-tested last night: a real GO negotiation against an actual TV
succeeded (P2P-GO-NEG-SUCCESS), but forming the actual data connection
failed with P2P-GROUP-FORMATION-FAILURE while the laptop stayed
connected to its normal STA WiFi -- completing the cast needs three
concurrent interfaces (STA + P2P-Device + the new P2P-Client group
link), and RTW89_MAX_INTERFACE_NUM was deliberately left at 2 in the
v1 design.

Traced whether raising this strains the driver's separate,
firmware-capability-tied MCC (Multi-Channel-Concurrent) role limit,
NUM_OF_RTW89_MCC_ROLES (= 2, unrelated to this constant, chan.h:51):
it does not. rtw89_entity_mgnt's active_roles[]/chanctx_tbl[][] arrays
(sized by RTW89_MAX_INTERFACE_NUM) are only populated for links with
chanctx_assigned == true, which is set in exactly one place --
rtw89_chanctx_ops_assign_vif(), the assign_vif_chanctx driver op --
and a P2P-Device vif's remain_on_channel is dispatched straight to the
driver's native ROC op, bypassing assign_vif_chanctx entirely (already
established: this only applies to emulate_chanctx-less drivers, which
this chip is not). So a P2P-Device link's chanctx_assigned stays false
for its whole lifetime and never occupies an MCC-role slot -- in the
real STA+P2P-Device+P2P-Client scenario, only STA and the P2P-Client
link ever get a real chanctx assignment, exactly matching
NUM_OF_RTW89_MCC_ROLES = 2, unchanged and unstrained.

The actual P2P-GROUP-FORMATION-FAILURE originates purely at the
mac80211/cfg80211 layer (ieee80211_check_combinations(), a plain
interface-count check against wiphy->iface_combinations[].max_interfaces,
itself set from this constant) -- this one-line change is the complete
fix for that. rtw89_iface_combs[]'s max_interfaces fields and
rtw89_entity_mgnt's array sizes already reference the macro
symbolically, so both grow automatically with no separate edit.
static_assert(RTW89_MAX_INTERFACE_NUM >= NUM_OF_RTW89_MCC_ROLES) still
holds (3 >= 2). Full research trail in this project's BUILD_LOG.md.

Signed-off-by: andres parra <[email protected]>
---
 core.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core.h b/core.h
index 2b21d96..83675f0 100644
--- a/core.h
+++ b/core.h
@@ -6340,7 +6340,7 @@ enum rtw89_entity_mode {
 	RTW89_ENTITY_MODE_UNHANDLED = -ESRCH,
 };
 
-#define RTW89_MAX_INTERFACE_NUM 2
+#define RTW89_MAX_INTERFACE_NUM 3
 
 /* only valid when running with chanctx_ops */
 struct rtw89_entity_mgnt {
-- 
2.55.0