『循名責實』談何容易？比方說

root@LEDE:~# cat /etc/config/wireless

config wifi-device ‘radio0‘
option type ‘mac80211’
option channel ’11’
option hwmode ’11g’
option path ‘platform/soc/3f300000.mmc/mmc_host/mmc1/mmc1:0001/mmc1:0001:1’
option htmode ‘HT20’
option disabled ‘0’

config wifi-iface ‘default_radio0’
option device ‘radio0‘
option network ‘lan’
option mode ‘ap’
option ssid ‘LEDE-RPI-3B’
option encryption ‘psk2+ccmp’
option key ‘12345678’

分明沒有定義 wlan0 ！那麼它打哪來的呢？？

root@LEDE:~# ifconfig 
br-lan    Link encap:Ethernet  HWaddr B8:27:EB:97:E5:3B  
          inet addr:5.168.166.88  Bcast:5.168.166.255  Mask:255.255.255.0
          inet6 addr: fe80::ba27:ebff:fe97:e53b/64 Scope:Link
          inet6 addr: fd42:80c5:b618::1/60 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:50 errors:0 dropped:0 overruns:0 frame:0
          TX packets:29 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:7070 (6.9 KiB)  TX bytes:4688 (4.5 KiB)

br-wan    Link encap:Ethernet  HWaddr B8:27:EB:C2:B0:6E  
          inet addr:5.168.168.9  Bcast:5.168.168.255  Mask:255.255.255.0
          inet6 addr: fe80::ba27:ebff:fec2:b06e/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5531 errors:0 dropped:2067 overruns:0 frame:0
          TX packets:2641 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:898901 (877.8 KiB)  TX bytes:598999 (584.9 KiB)

eth0      Link encap:Ethernet  HWaddr B8:27:EB:C2:B0:6E  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5531 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2641 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:898901 (877.8 KiB)  TX bytes:630039 (615.2 KiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:76 errors:0 dropped:0 overruns:0 frame:0
          TX packets:76 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1 
          RX bytes:7379 (7.2 KiB)  TX bytes:7379 (7.2 KiB)

wlan0     Link encap:Ethernet  HWaddr B8:27:EB:97:E5:3B  
          inet6 addr: fe80::ba27:ebff:fe97:e53b/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:50 errors:0 dropped:0 overruns:0 frame:0
          TX packets:83 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:7070 (6.9 KiB)  TX bytes:15160 (14.8 KiB)

處於科技快速變化之時代，文獻新舊駁雜，傳統與現在正交替︰

Linux Network Interfaces

Types of network interfaces

Physical Network Interfaces

Virtual Network Interfaces

Types of Virtual Network Interfaces

ip link add link eth0 eth0.1000 type vlan proto 802.1ad id 1000
ip link add link eth0.1000 eth0.1000.1000 type vlan proto 802.1q id 1000

• bridgeds: br0, br-lan
  are used to make multiple virtual or physical network interfaces act as if they were just one network interface (quasi the opposite of VLANs). Can also be used for VPN and bridged interfaces. The Linux Ethernet bridge can be used for connecting multiple Ethernet devices together. The connecting is fully transparent: hosts connected to one Ethernet device see hosts connected to the other Ethernet devices directly. understanding how bridge-interfaces work
• tunnel interfaces: pppoe-dsl, pppoa-dsl, tun0, vpn1,
  used to send packets over a tunneling protocol such as GRE, IPsec PPPoE, etc.
• special purpose: imq0, teql3
  used to change the order of outgoing network packets, or incoming network packet
• wireless operating mode virtual interfaces: wlan0, wlan0_1, ath3, ath_monitor, ..
  Linux wireless subsystem: There is always one physical network interface for each WNIC called the master interface. The master interface is invisible. Then, depending on the wireless operating mode the master interface is configured to, ad-hoc (IBSS), managed , AP , WDS, mesh point, monitor, wireless virtual network interfaces with different properties are created. This is done automatically by default. When the WNIC driver is loaded, there always will be the master interface and (at least) one virtual interface!

Two network interfaces can also be bonded together (please see Link aggregation and Channel bonding and Ubuntu Wiki), Documentation/networking/bonding.txt

UCI is a small C utility designed to centralize configuration in OpenWrt. /etc/config/network is the network configuration file. /etc/config/wireless is the wireless configuration file. UCI creates an abstraction layer for configuring network interfaces: In /etc/config/network you allocate a name like lan or internet_wire or whatever to each ifname-variable for every device and then this name is consistently used through the entire UCI configuration. But this can only be used in conjunction with UCI!

OpenWrt default configuration

叫人苦惱也！！

誰能先知 option path 出自何方？☻

Wireless configuration

The wireless UCI configuration is located in /etc/config/wireless. Learn about the entire IEEE 802.11 “wireless” subsystem.

Note1: By default the wireless is OFF. You can turn it on in the /etc/config/wireless by changing disabled 1 to disabled 0 In UCI CLI you do this with: uci set wireless.@wifi-device[0].disabled=0; uci commit wireless; wifi ote2: If your device contains multiple radios (e.g. some dual-band devices), then you’ll need to enabled each device in-turn – list disabled devices with uci show wireless | grep disabled Note3: In case your image does not contain the driver for your wireless chipset, simply install them with opkg and proceed withRegenerate Configuration.

Sections

Wifi Devices

config 'wifi-device' 'wl0'
        option 'type'    'broadcom'
        option 'channel' '6'

Common Device Options

……

MAC80211 Device Options

※ 註︰

sysfs

sysfs is a pseudo file system provided by the Linux kernel that exports information about various kernel subsystems, hardware devices, and associated device drivers from the kernel’s device model to user space through virtual files.^[1] In addition to providing information about various devices and kernel subsystems, exported virtual files are also used for their configuration.

sysfs provides functionality similar to the sysctl mechanism found in BSD operating systems, with the difference that sysfs is implemented as a virtual file system instead of being a purpose-built kernel mechanism, and that, in Linux, sysctl configuration parameters are made available at /proc/sys/ as part of procfs, not sysfs which is mounted at /sys/.^[2]

History

During the 2.5 development cycle, the Linux driver model was introduced to fix several shortcomings of version 2.4:

• No unified method of representing driver-device relationships existed.
• There was no generic hotplug mechanism.
• procfs was cluttered with non-process information.

Sysfs was designed to export the information present in the device tree which would then no longer clutter up procfs. It was written by Patrick Mochel.^[3][4] Maneesh Soni later wrote the sysfs backing store patch to reduce memory usage on large systems.

During the next year of 2.5 development the infrastructural capabilities of the driver model and driverfs, formerly called ddfs, began to prove useful to other subsystems.^[5][6] kobjects were developed to provide a central object management mechanism and driverfs was renamed to sysfs to represent its subsystem agnosticism.

Sysfs is mounted under the /sys mount point. If it is not mounted during initialization, you can always mount it using the command: “mount -t sysfs sysfs /sys”

Supported buses

PCI

Exports information about PCI devices.

USB

Contains both USB devices and USB hosts.

S/390 buses

As the S/390 architecture contains devices not found elsewhere, special buses have been created:

• css: Contains subchannels (currently the only driver provided is for I/O subchannels).
• ccw: Contains channel attached devices (driven by CCWs).
• ccwgroup: Artificial devices, created by the user and consisting of ccw devices. Replaces some of the 2.4 chandev functionality.
• iucv: Artificial devices like netiucv devices which use VM’s IUCV interface.

Sysfs and userspace

Sysfs is used by several utilities to access information about hardware and its driver (kernel modules) such as udev or HAL. Scripts have been written to access information previously obtained via procfs, and some scripts configure device drivers and devices via their attributes.

假使安裝『老工具』︰

opkg update
opkg install wireless-tools

或可一窺堂奧乎？☆

root@LEDE:~# iwconfig
wlan0 IEEE 802.11 Mode:Master Tx-Power=31 dBm
RTS thr:off Fragment thr:off
Power Management:on

br-wan no wireless extensions.

lo no wireless extensions.

eth0 no wireless extensions.

br-lan no wireless extensions.

然而『多功能』 IC 晶片越來越多︰

root@LEDE:~# dmesg | grep brcmfmac
[    6.052003] brcmfmac: brcmf_fw_map_chip_to_name: using brcm/brcmfmac43430-sdio.bin for chip 0x00a9a6(43430) rev 0x000001
[    6.187644] brcmfmac: brcmf_c_preinit_dcmds: Firmware version = wl0: Aug 29 2016 20:48:16 version 7.45.41.26 (r640327) FWID 01-4527cfab
[    6.236390] usbcore: registered new interface driver brcmfmac

root@LEDE:/sys/bus/sdio/drivers/brcmfmac# ls -l
--w-------    1 root     root          4096 Oct  6 15:33 bind
lrwxrwxrwx    1 root     root             0 Oct  6 15:33 mmc1:0001:1 -> ../../../../devices/platform/soc/3f300000.mmc/mmc_host/mmc1/mmc1:0001/mmc1:0001:1
lrwxrwxrwx    1 root     root             0 Oct  6 15:33 mmc1:0001:2 -> ../../../../devices/platform/soc/3f300000.mmc/mmc_host/mmc1/mmc1:0001/mmc1:0001:2
lrwxrwxrwx    1 root     root             0 Oct  6 15:33 module -> ../../../../module/brcmfmac
--w-------    1 root     root          4096 Oct  6 15:33 uevent
--w-------    1 root     root          4096 Oct  6 15:33 unbind


root@LEDE:/sys/bus/sdio/drivers/brcmfmac# cd mmc1\:0001\:1/
root@LEDE:/sys/devices/platform/soc/3f300000.mmc/mmc_host/mmc1/mmc1:0001/mmc1:0001:1# ls
class      driver     modalias   power      uevent
device     ieee80211  net        subsystem  vendor
root@LEDE:/sys/devices/platform/soc/3f300000.mmc/mmc_host/mmc1/mmc1:0001/mmc1:0001:1# cd ..

root@LEDE:/sys/bus/sdio/drivers/brcmfmac# cd mmc1\:0001\:2
root@LEDE:/sys/devices/platform/soc/3f300000.mmc/mmc_host/mmc1/mmc1:0001/mmc1:0001:2# ls
class      driver     power      uevent
device     modalias   subsystem  vendor

這個『mmc1\:0001\:2』到底是什麼東東耶？★