Architecture Overview

The MediaTek mt76 WiFi driver is a Linux kernel module that provides support for MediaTek wireless chipsets. The module follows a layered architecture with shared libraries for common functionality and chipset-specific drivers for hardware variations.

Module Layering

┌─────────────────────────────────────────────────────────┐
│              Linux Kernel (mac80211)                    │
│         IEEE 802.11 stack, netdev, PCI/USB              │
└────────────────────┬────────────────────────────────────┘
                     │
┌────────────────────▼────────────────────────────────────┐
│              Core Layer (mt76/)                         │
│  • mac80211.c    - mac80211 ops registration            │
│  • dma.c         - DMA ring buffer management           │
│  • mcu.c         - MCU communication base               │
│  • tx.c          - TX path processing                   │
│  • agg-rx.c      - RX aggregation                       │
│  • mmio.c        - Memory-mapped I/O                    │
│  • usb.c/sdio.c  - USB/SDIO bus operations              │
└────────────────────┬────────────────────────────────────┘
                     │
┌────────────────────▼────────────────────────────────────┐
│         Chipset Library Layer                           │
│  • mt792x-lib      - MT7921/MT7925 shared code          │
│  • mt76-connac-lib - Connac architecture (MT7615+)      │
│  • mt76x02-lib     - MT7602/MT7612 shared code          │
└────────────────────┬────────────────────────────────────┘
                     │
┌────────────────────▼────────────────────────────────────┐
│      Chipset Driver Layer                               │
│  • mt7925/  - MT7925 specific implementation            │
│  • mt7921/  - MT7921 specific implementation            │
│  • mt7915/  - MT7915 specific implementation            │
└────────────────────┬────────────────────────────────────┘
                     │
┌────────────────────▼────────────────────────────────────┐
│              Hardware (PCIe/USB)                        │
│         MediaTek WiFi chipsets                          │
└─────────────────────────────────────────────────────────┘

Module Dependencies

mt7925e.ko (PCIe driver)
    ├── depends on: mt7925-common.ko
    │   ├── depends on: mt792x-lib.ko
    │   │   ├── depends on: mt76-connac-lib.ko
    │   │   │   └── depends on: mt76.ko
    │   │   └── depends on: mt76.ko
    │   └── depends on: mt76.ko
    └── depends on: mt76.ko

Core Data Structures

Structure	Description
mt76_dev	Base device structure (all chipsets)
mt76_phy	PHY abstraction (supports multi-band)
mt76_wcid	Wireless Client ID (per-station/per-interface)
mt76_queue	DMA ring buffer descriptor
mt792x_dev	MT792x device state
mt792x_vif	Virtual interface state
mt792x_sta	Station state (MLO-aware)

Pages in This Section

• Multi-Link Operation

  ---

  WiFi 7 MLO support with up to 4 simultaneous links

  MLO docs

• Locking

  ---

  Mutex patterns and lock ordering

  Locking guide

• MCU Protocol

  ---

  Firmware communication protocol

  MCU docs

• Supported Chipsets

  ---

  MT7925, MT7921, and related hardware

  Chipset info

Key Design Patterns

1. Mutex Protection

All MCU operations must be protected by dev->mt76.mutex:

mt792x_mutex_acquire(dev);
/* MCU operations here */
mt792x_mutex_release(dev);

Common Bug

Missing mutex protection around ieee80211_iterate_active_interfaces() callbacks that call MCU functions.

2. MLO Link State Management

Always check for NULL when accessing MLO links:

struct mt792x_link_sta *mlink = mt792x_sta_to_link(msta, link_id);
if (!mlink)
    return -EINVAL;

3. RCU-Protected Access

MLO link configs are RCU-protected:

struct mt792x_bss_conf *mconf = rcu_dereference_protected(
    mvif->link_conf[link_id],
    lockdep_is_held(&dev->mt76.mutex)
);

Bus Abstraction

The module supports three bus types via struct mt76_bus_ops:

Bus	Description	Used By
MMIO (PCIe)	Memory-mapped I/O	MT7925e, MT7915e
USB	USB control transfers	MT7925u, MT7921u
SDIO	SDIO commands	MT7921s