WiFi Research

Issue

Currently, the internal WiFi chip cannot be used on any of the Replicant-supported devices without having to load non-free firmware. See Replicant status and the device pages for more information.

On desktops and laptops, several WiFi chips don't require non-free firmwares to be loaded.

Several cases exist:
  • The WiFi chip doesn't need a firmware, and the driver talks directly to the hardware (ath5k and ath9k compatible chips)
  • The WiFi chip has a free software firmware (ath9k_htc, carl1970, and some b43 compatible chips)
  • The WiFi chip has a non-free firmware in a flash chip and don't need loadable firmware.

On phones, the only WiFi chip that don't requires a non-free firmware that we know of is the OpenMoko FreeRunner wifi chip. The firmware is in a flash chip.

The idea here is to find ways to still get WiFi on Replicant Supported devices, without needing to load any non-free firmware.

WiFi Drivers and Firmwares types

Either the firmware implements the WiFi operations (scanning, association, and so on), either the driver implements it.

Firmware implementing the WiFi operations

This is also known as Hard-MAC.
An easy way to find out is to look into the WiFi driver Kconfig for "select CFG80211" or "depends CFG80211"

Example:

config LIBERTAS
        tristate "Marvell 8xxx Libertas WLAN driver support" 
        depends on CFG80211
[...]

If it is implemented by the firmware, it often contains bugs which cannot be fixed by the community. That also severally limit the use case of such WiFi chip beyond its most common uses cases.

This can result in more help in getting a free software firmware to run on such chip. However the amount of work to re-implement such firmware may be bigger.

The best way to reimplement it would be to write a new driver taking care of such WiFi operations and to make the fimrware do the smallest amount of work possible.

Driver implementing the WiFi operations

This is also known as Soft-MAC.
An easy way to find out is to look into the WiFi driver Kconfig for "select MAC80211" or "depends MAC80211"

Example:

config WL1251
        tristate "TI wl1251 driver support" 
        depends on MAC80211
[...]

Internal WiFi chips on devices currently targeted by Replicant

Device WiFi chip driver(s)
Galaxy S Broadcom BCM4329 BCMDHD (cfg80211)
LG Optimus Black
Nexus S
Galaxy Nexus Broadcom BCM4330
Galaxy Note
Galaxy S2
Galaxy S3 Broadcom BCM4334
GTA04 Marvell 8686 (W2CBW003) libertas_sdio(mainline, cfg80211)
libertas_tf_sdio(patches, mac80211)

Available Internal WiFi chips for smartphones and tablets

Driver Busses Firmware Issues
ath5k PCI, PCIe, PCMCIA, AHB None(Driver<->Hardware) Busses? chip size? power consumption?
ath9k PCI, PCIe, PCMCIA, AHB None(Driver<->Hardware) Busses? chip size? power consumption?
ath9k_htc USB Free firmware Bus? chip size? power consumption?
carl9170 USB Free firmware Bus? chip size? power consumption?
airo PCI, PCMCIA Non-free firmware on flash ?
at76c50x-usb USB Non-free firmware needed for some cards only ?
b43/b43-legacy SSB, PCI, PCI-E, PCMCIA OpenFWWF with 4306, 4311(rev1), 4318, 4320 ?
rt2400 PCI No non-free firmware needed ?
rt2500 PCI No non-free firmware needed ?
rt2500usb PCI No non-free firmware needed ?
rtl818x PCI, USB No non-free firmware needed ?
esp8266 UART, SPI, SDIO Part of the code in bootrom, standalone free firmware available, Out of tree Linux driver available ?
Notes:
  • PCI, PCIe and PCMCIA are available on very few SOCs (Like I.MX)
  • We are not aware of phone designs using USB wifi chips.
  • AHB and SSB are usually used as internal memory bus for SOCS. Maybe it can be used to connect a wifi chip to the SOC memory, like with the I.MX WEIM bus?
  • Chip Size is important to fit inside a phone. Might be less an issue for tablets.
References:

Internal WiFi chips on devices currently targeted by Replicant

External Wifi solution

Most/All Replicant supported devices support USB OTG. With the proper (standard) cable, the USB port of the device can do USB host.

However devices differ a lot in the number of Milli-ampers they can deliver trough that USB port. Some phones also have USB host enabled by default in their kernel configuration, and some other require patching the kernel.

On Replicant kernels, USB WiFi drivers are probably not compiled in by default. So you will also need to recompile.

Device Replicant Kernel Max mA
Galaxy Nexus
Galaxy Note
Galaxy Note 2
Galaxy S
Galaxy S 2
Galaxy S 3
Galaxy Tab 2 7.0
Galaxy Tab 2 10.1
GTA04
Nexus S
Optimus Black

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