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I'm not from the US so not really familiar with FCC regulations. > If you've got silicon that has to conform with FCC regulations it's going to have non-modifi

I'm not from the US so not really familiar with FCC regulations. > If you've got silicon that has to conform with FCC regulations it's going to have non-modifiable firmware. Can you explain 'why?' or maybe throw me a link or two? Thanks!

Pet_Ant 3y ago
I think it is because the firmware guarantees that the radio behaves according to specifications. Much like the governor on a car.
- megous 3y ago
  Can you explain wifi chips like rtl8852 that have power levels and channels specified in the linux drivers and are fcc certified, then?
  - giantrobot 3y ago
    It only has power level control up to the limits for ISM devices on its operating frequencies. Its license is only valid for antennas with specific gain. You technically can overwrite its firmware to turn the radio into some general purpose software defined radio transmitter but that's not how the device is licensed and sold.
    - jchw 3y ago
      Wait, though. Doesn't that seem to make this point moot? If they're not responsible for what users do hacking around, then there's not really any need to keep firmware closed source or locked down. To be fair, I think at least at one point, that is in fact how it worked. I recall having a wrt54g and being able to run it out-of-spec using DD-WRT.
      - giantrobot 3y ago
        > Doesn't that seem to make this point moot? If they're not responsible for what users do hacking around, then there's not really any need to keep firmware closed source or locked down. To sell the device the manufacturer has to make sure the device follows regulations and normal usage will follow end user regulations. The easier they make it for regulation-violating user modifications the more likely the product is to not get a license for sale of the device. In something where the radio baseband is a physical circuit layout conformance is easy. Without modifying surface mount parts that circuit will always conform to its license. For complicated basebands (WiFi etc) with software control having a fixed/closed firmware is the easiest way to get a license and not get it pulled after the fact. The WRT54G is a fluke because it ended up using Linux/GPL code in the firmware. It was then obliged to release the source because of that. You can buy devices that allow firmware development and modification but not at retail and you can't offer them for sale without an FCC license covering them.
        Pet_Ant 3y ago
        Okay, but you could release the source code for the firmware, and only accept a signed binary blob. This would still be open source (GPL v2 compliant, but not v3 AFAIK) and auditable, but it still be conforming and certifiable.
        giantrobot 3y ago
        And some manufacturers do just that. Many do not because they're sub-licensing components/code from other companies. Others don't because they want to license their hardware to others and firmware source is a special sauce when the functions of the radio are all in software.
        pabs3 3y ago
        This is what the Intel Sound "open" Firmware does, and it is incredibly annoying. https://github.com/thesofproject/sof/issues/5814 https://github.com/thesofproject/sof/issues/5814 I don't think that would be GPLv2 compliant either: https://sfconservancy.org/blog/2021/mar/25/install-gplv2/ https://sfconservancy.org/blog/2021/mar/25/install-gplv2/ https://sfconservancy.org/blog/2021/jul/23/tivoization-and-the-gpl-right-to-install/ https://sfconservancy.org/blog/2021/jul/23/tivoization-and-t...
    - megous 3y ago
      You can use channels not allowed in your country. The firmware doesn't prevent that.
      - giantrobot 3y ago
        A device SKU only meant to be sold in ITU region 2 or North America specifically will often have the available bands/channels locked in the firmware despite the capability of the underlying hardware. Same for a SKU meant for other ITU regions or countries. It's far less common to have user selectable region settings for things like WiFi channels. It used to be more common but regional SKUs are just easier for everyone involved. Even if a device enables you to specify channels not allowed in your country/region doesn't mean you're legally in the clear. "But there's a switch" isn't a defense against an FCC fine. It's unlikely you'll get caught and fined for using channels 12-14 on a Wifi device in the US but if you interfere with something important you're breaking several laws and if caught can potentially face jail time.
        megous 3y ago
        Allright, so firmware lock is not a requirement then?
giantrobot 3y ago
The why is simple: Power/frequency limits allow everybody to be able to use personal consumer devices without licensing and without preventing other people from using their devices. If you modified your WiFi to blast out a 10W signal across multiple channels at your house, you completely ruin my ability to use Wifi at my house next door. Radio spectrum is shared by everybody. As for reading there's CFR title 47 [0]. Parts 15 and 18 are germane for unlicensed radios and electronic devices. Parts 22 and 24 cover cellular devices. The regulations don't explicitly say anything about firmware but to build devices that follow the regulations end user modifiable firmware is an implicit restriction. Even user serviceable antennas are restricted because radio device licenses cover not just the electrical output but total gain of the shipped antenna. [0] https://www.ecfr.gov/current/title-47 https://www.ecfr.gov/current/title-47
- AnthonyMouse 3y ago
  > The why is simple: Power/frequency limits allow everybody to be able to use personal consumer devices without licensing and without preventing other people from using their devices. That explains why there are power/frequency limits, not why the device manufacturer should be deputized into responsibility for a sophisticated user's non-compliant device modifications. Anyone can make an arc gap transmitter for morse code out of $3 in bits from any hardware store that will interfere with anybody else's radio devices in the vicinity. Anyone can buy ham radio equipment or built it from parts and do all kinds of non-compliant things with it. Then the FCC comes after you, not the hardware store or the device OEM. Or more likely in the case of a WiFi device, comes after the person distributing custom firmware that purposely exposes a simple knob to allow unsophisticated users to exceed regulatory limits. And if DD-WRT did that, they should expect a visit from The Government. But what should that have anything to do with Linksys or Netgear? There aren't enough end users who know how to modify the firmware code themselves to matter, even if you make that "easy."
  - giantrobot 3y ago
    > There aren't enough end users who know how to modify the firmware code themselves to matter, even if you make that "easy." This is just a silly statement. Go to an apartment complex sometime and browse the available WiFi networks. You'll see a huge number of them because everyone has the output power on their router set to the max value. There's plenty of places the 2.4GHz band is simply unusable because the noise floor is so high from a hundred base stations blasting out at full power. If WifiBoost.exe could in tease that output power enough people would do it that WiFi or Bluetooth in some places would be completely unusable. Modern radio basebands are largely software defined. The modulation/keying, power output, and transmitted bands are all defined in software. In order to sell that silicon as a Part 15 compliant device to end users the firmware needs to be locked. It's the digital equivalent of a fixed function radio. A manufacturer of a fixed function radio couldn't get a Part 15 license if it had a potentiometer on the back allowing you to dial up the output power, even if that potentiometer was locked under the case most people wouldn't open. With an SDR the hardware plus software is considered the "device" for licensing purposes. If it supported unlocked or modifiable firmware it couldn't be easily/at all sold as a Part 15 device. It would be a different class of device and would require the end user to have a license to operate it.

Pet_Ant 3y ago

I think it is because the firmware guarantees that the radio behaves according to specifications. Much like the governor on a car.

megous 3y ago
Can you explain wifi chips like rtl8852 that have power levels and channels specified in the linux drivers and are fcc certified, then?
- giantrobot 3y ago
  It only has power level control up to the limits for ISM devices on its operating frequencies. Its license is only valid for antennas with specific gain. You technically can overwrite its firmware to turn the radio into some general purpose software defined radio transmitter but that's not how the device is licensed and sold.
  - jchw 3y ago
    Wait, though. Doesn't that seem to make this point moot? If they're not responsible for what users do hacking around, then there's not really any need to keep firmware closed source or locked down. To be fair, I think at least at one point, that is in fact how it worked. I recall having a wrt54g and being able to run it out-of-spec using DD-WRT.
    - giantrobot 3y ago
      > Doesn't that seem to make this point moot? If they're not responsible for what users do hacking around, then there's not really any need to keep firmware closed source or locked down. To sell the device the manufacturer has to make sure the device follows regulations and normal usage will follow end user regulations. The easier they make it for regulation-violating user modifications the more likely the product is to not get a license for sale of the device. In something where the radio baseband is a physical circuit layout conformance is easy. Without modifying surface mount parts that circuit will always conform to its license. For complicated basebands (WiFi etc) with software control having a fixed/closed firmware is the easiest way to get a license and not get it pulled after the fact. The WRT54G is a fluke because it ended up using Linux/GPL code in the firmware. It was then obliged to release the source because of that. You can buy devices that allow firmware development and modification but not at retail and you can't offer them for sale without an FCC license covering them.
      - Pet_Ant 3y ago
        Okay, but you could release the source code for the firmware, and only accept a signed binary blob. This would still be open source (GPL v2 compliant, but not v3 AFAIK) and auditable, but it still be conforming and certifiable.
        giantrobot 3y ago
        And some manufacturers do just that. Many do not because they're sub-licensing components/code from other companies. Others don't because they want to license their hardware to others and firmware source is a special sauce when the functions of the radio are all in software.
        pabs3 3y ago
        This is what the Intel Sound "open" Firmware does, and it is incredibly annoying. https://github.com/thesofproject/sof/issues/5814 https://github.com/thesofproject/sof/issues/5814 I don't think that would be GPLv2 compliant either: https://sfconservancy.org/blog/2021/mar/25/install-gplv2/ https://sfconservancy.org/blog/2021/mar/25/install-gplv2/ https://sfconservancy.org/blog/2021/jul/23/tivoization-and-the-gpl-right-to-install/ https://sfconservancy.org/blog/2021/jul/23/tivoization-and-t...
  - megous 3y ago
    You can use channels not allowed in your country. The firmware doesn't prevent that.
    - giantrobot 3y ago
      A device SKU only meant to be sold in ITU region 2 or North America specifically will often have the available bands/channels locked in the firmware despite the capability of the underlying hardware. Same for a SKU meant for other ITU regions or countries. It's far less common to have user selectable region settings for things like WiFi channels. It used to be more common but regional SKUs are just easier for everyone involved. Even if a device enables you to specify channels not allowed in your country/region doesn't mean you're legally in the clear. "But there's a switch" isn't a defense against an FCC fine. It's unlikely you'll get caught and fined for using channels 12-14 on a Wifi device in the US but if you interfere with something important you're breaking several laws and if caught can potentially face jail time.
      - megous 3y ago
        Allright, so firmware lock is not a requirement then?

giantrobot 3y ago

The why is simple: Power/frequency limits allow everybody to be able to use personal consumer devices without licensing and without preventing other people from using their devices. If you modified your WiFi to blast out a 10W signal across multiple channels at your house, you completely ruin my ability to use Wifi at my house next door. Radio spectrum is shared by everybody. As for reading there's CFR title 47 [0]. Parts 15 and 18 are germane for unlicensed radios and electronic devices. Parts 22 and 24 cover cellular devices. The regulations don't explicitly say anything about firmware but to build devices that follow the regulations end user modifiable firmware is an implicit restriction. Even user serviceable antennas are restricted because radio device licenses cover not just the electrical output but total gain of the shipped antenna. [0] https://www.ecfr.gov/current/title-47 https://www.ecfr.gov/current/title-47

AnthonyMouse 3y ago
> The why is simple: Power/frequency limits allow everybody to be able to use personal consumer devices without licensing and without preventing other people from using their devices. That explains why there are power/frequency limits, not why the device manufacturer should be deputized into responsibility for a sophisticated user's non-compliant device modifications. Anyone can make an arc gap transmitter for morse code out of $3 in bits from any hardware store that will interfere with anybody else's radio devices in the vicinity. Anyone can buy ham radio equipment or built it from parts and do all kinds of non-compliant things with it. Then the FCC comes after you, not the hardware store or the device OEM. Or more likely in the case of a WiFi device, comes after the person distributing custom firmware that purposely exposes a simple knob to allow unsophisticated users to exceed regulatory limits. And if DD-WRT did that, they should expect a visit from The Government. But what should that have anything to do with Linksys or Netgear? There aren't enough end users who know how to modify the firmware code themselves to matter, even if you make that "easy."
- giantrobot 3y ago
  > There aren't enough end users who know how to modify the firmware code themselves to matter, even if you make that "easy." This is just a silly statement. Go to an apartment complex sometime and browse the available WiFi networks. You'll see a huge number of them because everyone has the output power on their router set to the max value. There's plenty of places the 2.4GHz band is simply unusable because the noise floor is so high from a hundred base stations blasting out at full power. If WifiBoost.exe could in tease that output power enough people would do it that WiFi or Bluetooth in some places would be completely unusable. Modern radio basebands are largely software defined. The modulation/keying, power output, and transmitted bands are all defined in software. In order to sell that silicon as a Part 15 compliant device to end users the firmware needs to be locked. It's the digital equivalent of a fixed function radio. A manufacturer of a fixed function radio couldn't get a Part 15 license if it had a potentiometer on the back allowing you to dial up the output power, even if that potentiometer was locked under the case most people wouldn't open. With an SDR the hardware plus software is considered the "device" for licensing purposes. If it supported unlocked or modifiable firmware it couldn't be easily/at all sold as a Part 15 device. It would be a different class of device and would require the end user to have a license to operate it.