WLAN overview

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本文介绍了WLAN框架的组成方式，配置方法以及使用方法。

Purpose

无线局域网（WLAN）是一种无线计算机网络，它使用无线通信链接两个或多个设备以在有限的区域内形成局域网（LAN），例如家庭，学校，计算机实验室，校园，办公楼等。 这使用户能够在该区域内四处移动，但仍可以连接到网络。通过网关，WLAN还可以提供与更广泛的Internet的连接。
Linux® 无线子系统包含两个主要模块：cfg80211和mac80211，它们帮助WiFi驱动程序与内核的其余部分和用户空间建立接口。
特别是，cfg80211在内核中提供配置管理服务。它还通过nl80211在内核和用户空间之间提供管理接口。
软MAC（soft MAC）设备和完整MAC设备都需要与cfg80211一起使用。 Mac80211是仅支持软件MAC设备的驱动程序API

WLAN可以在许多不同的用例中使用，如How to use WLAN部分所述：

System overview

Alternate text
WLAN Overview

Description of the components

从用户空间到硬件

  • 应用 (用户空间)

有许多使用WLAN的应用程序：例如Internet浏览器， 流应用程序，FTP应用程序。

  • WLAN工具 (用户空间)

有一组实用程序可以管理WLAN网络： Network tools

  • CFG80211 API (内核空间)

cfg80211[1] 是Linux中的IEEE 802.11[2] 设备的配置API。
- 它桥接了用户空间和驱动程序，并提供了与IEEE 802.11相关的某些实用程序功能。
-Linux中的所有现代无线驱动程序都必须通过mac80211直接或间接地使用它，以便它们通过nl80211提供一致的API[3].
- 它与 Netlink[4] socket 连接。

  • MAC80211框架 (内核空间)

MAC80211是Linux内核的一个子系统，它实现了软MAC/半MAC无线共享代码[5]

  • WLAN配套驱动程序 (内核空间)

WLAN配套驱动程序注册和控制WLAN设备。

  • MMC框架：MMC核心 (内核空间)

MMC内核”'确保与MultiMediaCard（MMC）嵌入式[6] / [7] / 安全数字规范安全数字输入/输出（SDIO )[8].
 MP1和WLAN设备之间的通信链接是SDIO总线。

  • SDMMC driver (Kernel space)

More information in MMC overview

  • STM32: SDMMC (Hardware)

More information in MMC overview

  • External devices (Hardware)

WLAN companion chip

APIs description

MAC80211 is new wireless driver API, which implements the shared code for soft-MAC/half-MAC wireless devices[9]

cfg80211[10] is the new driver configuration API for IEEE 802.11[11] devices in Linux.

Configuration

The WLAN API is not activated by default in ST deliveries. To active it, you can use Linux Menuconfig tool: Menuconfig or how to configure kernel and select:

For Network features: 

[*] Networking support  --->  
    [*] Networking options  --->
        [*] Packet socket 
        [*] TCP/IP networking
          [*] IP: kernel level autoconfiguration
            [*] IP: DHCP support
            [*] IP: BOOTP support
            [*] IP: RARP support
        [*] INET: socket monitoring interface
        [*] The IPv6 protocol
        [*] DNS Resolver support
    [*]   Wireless  --->
        [*]   cfg80211 - wireless configuration API
                [*]   cfg80211 wireless extensions compatibility
        [*]   Generic IEEE 802.11 Networking Stack (mac80211)

For example if the companion chip is Murata chip 1DX[12]

[*] Device Drivers  --->
    [*]   Network device support  --->
        [*]   Wireless LAN  --->
             [*]   Broadcom devices
                [*]   Broadcom FullMAC WLAN driver

For STM32 SDMMC : see SDMMC configuration

Device tree

The DT bindings documentation deals with all required or optional device tree properties.

Detailed DT configuration for STM32 peripherals: WLAN device tree configuration.

How to use WLAN

How to use the WLAN user space interface

Please see examples based on the following use cases:

How to trace and debug the framework

How to monitor

Please give instruction to help the developer/user to get information about this framework in the Linux file system

How to watch link quality

Proc filesystem provides information about Quality link: 

Board $> cat /proc/net/wireless 
Inter-| sta-|   Quality        |   Discarded packets               | Missed | WE
face | tus | link level noise |  nwid  crypt   frag  retry   misc | beacon | 22
wlan0: 0000    0     0     0        0      0      0      0      0        0

Example of stat: 

Board $> watch -d -n 3 "iw dev wlan0 station dump; iwconfig wlan0; cat /proc/net/wireless"

Every 3.0s: iw dev wlan0 station dump; iwconfig wlan0; cat /proc/net/wir...  stm32mp1: Sun Nov  4 16:32:52 2018

Station 00:16:b6:2c:47:36 (on wlan0)
       inactive time:  0 ms   
       rx bytes:       11001
       rx packets:     37
       tx bytes:       13077
       tx packets:     83
       tx failed:      0
       signal:         -72 [-72] dBm
       tx bitrate:     12.0 MBit/s
       rx bitrate:     1.0 MBit/s 
       authorized:     yes
       authenticated:  yes
       associated:     yes
       WMM/WME:        no
       TDLS peer:      yes
       DTIM period:    1
       beacon interval:100
       short preamble: yes
       short slot time:yes
       connected time: 55 seconds
wlan0     IEEE 802.11  ESSID:"NETWORK1"
         Mode:Managed  Frequency:2.462 GHz  Access Point: 00:16:B6:2C:47:36
         Bit Rate=12 Mb/s   Tx-Power=31 dBm
         Retry short limit:7   RTS thr:off   Fragment thr:off
         Encryption key:off
         Power Management:on
         Link Quality=38/70  Signal level=-72 dBm
         Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
         Tx excessive retries:0  Invalid misc:0   Missed beacon:0

Inter-| sta-|   Quality        |   Discarded packets               | Missed | WE
face | tus | link level noise |  nwid  crypt   frag  retry   misc | beacon | 22
wlan0: 0000   38.  -72.  -256        0      0      0      0      0        0

How to trace

This part is as example in case the companion chip is Murata chip

How to verify than the WLAN driver is well probed

  • In dmesg log, check "brcmfmac" logs :
[   67.306154] brcmfmac: brcmf_c_preinit_dcmds: Firmware version = wl0: Aug  6 2017 23:19:25 version 7.45.98.30 (r666241 CY) FWID 01-f0b000
[   67.326146] brcmfmac: brcmf_c_preinit_dcmds: CLM version = API: 12.2 Data: 7.11.15 Compiler: 1.24.2 ClmImport: 1.24.1 Creation: 2014-05 
[   67.676323] brcmfmac: brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)

How to debug the WLAN driver

Add dynamic debug firmware traces

Need to activate in the kernel config: CONFIG_DYNAMIC_DEBUG, more info on the dynamic debug How_to_use_the_kernel_dynamic_debug 

# cd /sys/kernel/debug/dynamic_debug/

Check all functions used to manage firmware: 

# cat control | grep firmware
drivers/base/firmware_class.c:339 [firmware_class]__fw_free_buf =_ "%s: fw-%s buf=%p data=%p size=%u\012"
drivers/base/firmware_class.c:462 [firmware_class]fw_set_page_data =_ "%s: fw-%s buf=%p data=%p size=%u\012"
drivers/base/firmware_class.c:1102 [firmware_class]_request_firmware_prepare =_ "using built-in %s\012"
drivers/base/firmware_class.c:290 [firmware_class]__allocate_fw_buf =_ "%s: fw-%s buf=%p\012"
drivers/base/firmware_class.c:1194 [firmware_class]_request_firmware =_ "firmware: %s loading timed out\012"
drivers/base/firmware_class.c:423 [firmware_class]fw_get_filesystem_firmware =_ "loading %s failed with error %d\012"
drivers/base/firmware_class.c:429 [firmware_class]fw_get_filesystem_firmware =_ "direct-loading %s\012"

Add print info "+p" in all firmware functions (p: causes a printk() message to be emitted to dmesg) 

# echo "file drivers/base/firmware_class.c +p" > control

Now "p" option is added in all firmware functions. 

# cat control | grep firmware
drivers/base/firmware_class.c:339 [firmware_class]__fw_free_buf =p "%s: fw-%s buf=%p data=%p size=%u\012"
drivers/base/firmware_class.c:462 [firmware_class]fw_set_page_data =p "%s: fw-%s buf=%p data=%p size=%u\012"
drivers/base/firmware_class.c:1102 [firmware_class]_request_firmware_prepare =p "using built-in %s\012"
drivers/base/firmware_class.c:290 [firmware_class]__allocate_fw_buf =p "%s: fw-%s buf=%p\012"
drivers/base/firmware_class.c:1194 [firmware_class]_request_firmware =p "firmware: %s loading timed out\012"
drivers/base/firmware_class.c:423 [firmware_class]fw_get_filesystem_firmware =p "loading %s failed with error %d\012"
drivers/base/firmware_class.c:429 [firmware_class]fw_get_filesystem_firmware =p "direct-loading %s\012"
FMAC debug
Enable debug features in the defconfig file
  • Enable CPTCFG_BRCMDBG and CONFIG_DEBUG_FS
  • Rebuild your kernel
Enable brcmfmac debug log
  • Message levels are listed in drivers/net/wireless/broadcom/brcm80211/brcmfmac/debug.h 
/* message levels */
#define BRCMF_TRACE_VAL 0x00000002
#define BRCMF_INFO_VAL 0x00000004
#define BRCMF_DATA_VAL 0x00000008
#define BRCMF_CTL_VAL 0x00000010
#define BRCMF_TIMER_VAL 0x00000020
#define BRCMF_HDRS_VAL 0x00000040
#define BRCMF_BYTES_VAL 0x00000080
#define BRCMF_INTR_VAL 0x00000100
#define BRCMF_GLOM_VAL 0x00000200
#define BRCMF_EVENT_VAL 0x00000400
#define BRCMF_BTA_VAL 0x00000800
#define BRCMF_FIL_VAL 0x00001000
#define BRCMF_USB_VAL 0x00002000
#define BRCMF_SCAN_VAL 0x00004000
#define BRCMF_CONN_VAL 0x00008000
#define BRCMF_BCDC_VAL 0x00010000
#define BRCMF_SDIO_VAL 0x00020000
#define BRCMF_MSGBUF_VAL 0x00040000
#define BRCMF_PCIE_VAL 0x00080000
#define BRCMF_FWCON_VAL 0x00100000

$ modprobe brcmfmac debug=${BRCMF_Message_Level}
$ dmesg -n 8
Examples
  • Add TRACE and INFO
$ modprobe brcmfmac debug=0x6
  • Add TRACE, INFO and SDIO
$ modprobe brcmfmac debug=0x20006
  • Add TRACE, INFO and WIFI_FW_LOG
$ modprobe brcmfmac debug=0x00100006
How to check wlreg_on status and voltage setting
$ cat /sys/kernel/debug/regulator/regulator_summary

Source code location

The source files are located inside the Linux kernel.

  • Broadcom wlan driver: of.c[13]

References

  1. ↑ [1], cfg80211
  2. ↑ [2], IEEE_802.11
  3. ↑ [3], nl80211
  4. ↑ [4], Netlink
  5. ↑ [5], mac80211
  6. ↑ MultiMediaCard, MultiMediaCard规范安全数字（SD）
  7. ↑ Secure Digital,
  8. ↑ Secure Digital Input Output, 安全数字输入输出规范
  9. ↑ [6], mac80211
  10. ↑ [7], cfg80211
  11. ↑ [8], IEEE_802.11
  12. ↑ [9], 1DX
  13. ↑ [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/net/wireless/broadcom/brcm80211/brcmfmac/of.c ],of.c
取自“http://wiki.100ask.org/index.php?title=WLAN_overview&oldid=7489”