WiFi Research¶

• Table of contents
• WiFi Research
  • Issue
  • WiFi Drivers and Firmwares types
    • Firmware implementing the WiFi operations
    • Driver implementing the WiFi operations
  • Internal WiFi chips on devices currently targeted by Replicant
  • Available Internal WiFi chips for smartphones and tablets
  • WiFi chip evaluation kit and hardware debug tools
    • TODO
  • Internal WiFi chips on devices currently targeted by Replicant
  • External Wifi solution

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.

• 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 doesn't require 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 firmware 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¶

Available Internal WiFi chips for smartphones and tablets¶

• 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.

• https://en.wikipedia.org/wiki/Comparison_of_open-source_wireless_drivers#Status
• https://wireless.wiki.kernel.org/en/users/drivers
• http://netweb.ing.unibs.it/~openfwwf/index.php
• https://nurdspace.nl/ESP8266

WiFi chip evaluation kit and hardware debug tools¶

• BCM4334 Evaluation kit

• ath9k_htc compatible chips: This probably would make it easier to modify the firmware to debug and improve power management
• Realtek 8188F compatible chips, because freeing the firmware should be doable

TODO¶

• Coordinate the work with the Libreplanet wiki
• Look into Broadcom chipset reverse engineering tools like nexmon . Since Broadcom chipsets have Bluetooth support on the same chip it is also worth to look into tools such as InternalBlue.

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 through 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.

See #1926 for pointers on how to find the missing information for the Maxim Power Management ICs (PMICs).