[Replicant] FAQ entry

Tue May 9 18:28:50 UTC 2017

On Sun, 07 May 2017 13:50:25 +0200
Paul Kocialkowski <paulk at replicant.us> wrote:

> Hi,
Hi,

> > == Does Replicant supports devices that can run free software modem
> > firmwares? ==
> > 
> > While a free software and functional modem firmwares do exist[1],
> > the smartphones supported[2] are probably not powerful enough[3] to
> > run recent versions of android[4] decently.
> > 
> > [1] https://osmocom.org/projects/baseband/wiki/
> > [2] The Openmoko GTA01 and GTA02
> > [3] They both have only 128M of RAM
> > [4] 340MB For Android 4.2[5], 424M For Android 6[6]
> > [5] 7.6. Memory and Storage in:
> > https://static.googleusercontent.com/media/source.android.com/en//compatibilit
> > y/4.2/android-4.2-cdd.pdf
> > [6] 7.6.1. Minimum Memory and Storage in:
> > https://static.googleusercontent.com/media/source.android.com/en//compatibilit
> > y/6.0/android-6.0-cdd.pdf   

> Since we're updating the website these days, I'm bumping this.
I've done a new version below.

I previoulsy mistakenly thought that the FAQ was not in the website
git, but it is, in about.php. I probably won't have the time to convert
that into HTML anytime soon though.

> I agree with the idea. We coudl also mention the feature phones built
> around microcontroller boards like the Arduino and explain why it's
> out of the scope of Replicant.
I've attempted to do it in the example below but it doesn't fit that
well into the overal context.

I'm also concerned about the fact that there is no clear distinction
between a modern SOC that can run GNU/Linux and a microcontroller.

To run GNU/Linux:
- You don't need an MMU: uClinux was merged long time ago in the linux
  kernel, and some architecture and SOC currently supported in linux are
  mmu-less.
- You probably don't even need RAM, some form of directly addressable
  memory like memory mapped flash chip might work.
- You still need some mimimum ammount of directly addressable memory.

Here's linux ported to an stm32f discovery board with 8M of
addressable memory:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/stm32f429-disco.dts?id=refs/tags/v4.11

Unrelated to Replicant, the issue is that with hardware that has too few
memory, you probably cannot do many useful thing with GNU/Linux as
running it would use too many resources that would have been available
otherwise (when using smaller OS or no OS at all). 

Here's a new version (not line wrapped):
> == Can Replicant be ported on any device? ==
> Replicant is based on the Android project, and therefor also inherit its minimum hardware requirements.
> As such it requires the processor running Replicant to have at least:
> - 340MB of RAM for Replicant 4.2 [1].
> - 424MB of RAM for Replicant 6 [2].
> 
> This unfortunately rules out many older Android devices that lack enough RAM to run recent versions of Android. Using older versions of Android is not practical either due the the difficulty to build such old software on recent GNU/Linux distributions, and the numerous security issues that were fixed in more recent Android versions.
> 
> It also rules out many do it yoursel mobile phones, like arduino based mobile phones as they do again do not have such ammount of RAM. Given the ammount of ram (Typically in the KB range) it wound't even be very possible or practical to have GNU/Linux running on theses.
> 
> [1] 7.6. Memory and Storage in:
> https://static.googleusercontent.com/media/source.android.com/en/compatibility/4.2/android-4.2-cdd.pdf
> [2] 7.6.1. Minimum Memory and Storage in:
> https://static.googleusercontent.com/media/source.android.com/en/compatibility/6.0/android-6.0-cdd.pdf
> 
> == Does Replicant intends to support devices that can run free software modem firmwares? ==
> 
> The only free software modem firmwares we are aware of are:
> - osmocomBB[1]: A functional modem firmware that is able to make calls, receive SMS and so on. Unfortunately it requires a GNU/Linux computer aside to run part of the GSM stack.
> - Some modified osmocomBB code meant for specific purposes, like mapping GSM networks security.
> - Nuttx[2]: Some osmocomBB devices were ported to it[3], but the osmocomBB GSM stack was not ported yet to Nuttx. That work was then removed from Nuttx[4] due to the lack of interest/time from the people involved in that port.
> 
> Note that some projects seems to have a free software modem firmware but do not:
> - The FreeCalypso[5] project is not free software. It uses source code that isn't under a free software license.
> - The quecktel-modem osmocom project[6] targets modems that runs GNU/Linux aside the proprietary modem firmware, on a separate processor.
> 
> The only working devices that can run the free software firmwares mentioned above do not met Android hardware requirement because:
> - They have only 128M of RAM, as it is the case for the Openmoko GTA01 and GTA02 smartphones.
> - They are not smartphones and have only one processor which is supposed to run the modem firmware. They also have even fewer RAM(Ranging from 256KB to 8MB).
> 
> [1] https://osmocom.org/projects/baseband/wiki/
> [2] http://nuttx.org
> [3] http://osmocom.org/projects/nuttx-bb/wiki
> [4] https://bitbucket.org/nuttx/nuttx/commits/f063e4c5ac041b6edfb1ab07a25f0c3fe9531966
> [5] https://www.freecalypso.org/
> [6] https://osmocom.org/projects/quectel-modems/wiki

Denis.
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