csantosb

As one understands with time and a bit of experience, keeping track of the whole bunch of #dependencies necessary to handle daily when doing digital hardware design may reveal as an error-prone task. And yet, this is not to speak about regressions, incompatibilities and most important, #reproducibility of results. Luckyly enough, this is precisely the problem that #guix intends to solve, in an elegant, minimalistic and open way, using only #freesoftware.
Functional package management is a paradigm pioneer by nix and developed by Eelco Dolstra in his influential PhD Thesis. It is based on building each of the nodes in the graph of dependencies based solely in its inputs, contents, and node definition, producing a new node. The process repeats for every single node in the graph. In what concerns operating systems and software management, this comes to a radical different approach to classical package management. Simply put, every new build lives its life, regardless of the remaining builds. This makes it possible to have access to the kind of advanced utilities which ease our lives: declarative configurations, profiles, rollbacks, generations, etc. Forget the dependency hell.
Guix is founded on a similar approach, keeping its own set of rules as it only packages #freesoftware. There are around 30.000 of them as for today, including all the usual suspects. Within the context of #modernhw, guix is to be understood as a dependency management tool with advanced capabilities. Sure, it handles software, but there is no reason to use it exclusively as a software manager. It may handle IP blocks, documentation, bibliographic references, and more generally, all what concerns #plaintext files in a #gitforge. It understands versions, licences, dependencies, repositories and all kinds of relationships between them. Furthermore, it embeds a pragmatic language, guile, to script package definitions, declaring the behavior of nodes in our graph of dependencies.
The most relevant feature of guix turns out to be its bootstraping capabilities. Full source bootstrap comes to building the whole dependency graph right from the bottom, based on a core minimum of trusted binary seeds. From that point upwards the whole distribution is self-contained, as all that it builds is included in guix itself. Any available package is founded on a package definition included in guix, its source code available online in a #git repository, and its dependencies. Each of the latest, follows the same rules, down to the bottom of the graph where a trust seed is necessary.
Why is this necessary and useful for #modernhw ? Because it provides #reproducibility for free, as reproducible builds are granted here. Turns out that this is at the very heart of guix and produces #determinism, meaning that same operations will produce same outputs, no matter when, no matter what, no matter where. Game over to ambiguity. Determinism, coupled to its declarative nature, reveals as a simple means to track our dependencies history without ambiguity.
Let’s take an example, and say we have a Vivado project in the form of a set of #tcl files. To build the logic of our favourite #fpga, we require also a couple of external firmware dependencies as IP block in their own git repositories, with tagged revisions, being mutually dependent and incompatible, following the tag in use. Not all of them are compliant with our project. Each of the firmware modules incorporates its own set of VHDL versioned dependencies, along with its associated documentation. We need to provide a python testing framework (you guess it), along with its verification libraries. We need to create a static web site with the instructions on how to download, instantiate, compile and deploy each different version of our project for a couple of thousand users out there, each with a different #gnulinux system, version and configuration of installed software and libraries. Take it for granted, each user need a different version of our project, as they need to guarantee compatibility with their own internal developments. And we need to provide the correct version of every tool, compatible with our code and scripts. The right version, I do mean. Not any random version.
Can you imagine the pain ? Now, suppose that you could describe in a couple of #plaintext manifest files the status of your project. End of the history. Users willing to reproduce your project and dependencies only need to git clone the manifest files and install them locally, regardless of their system, of their present libraries or of their abilities. No problem if the host OS doesn’t provide the necessary software, guix handles the situation. Users just do make and the whole project is deployed, tested and simulated, using the right version of each node in the graph. This is Guix at its best.
Not yet convinced ? Take a look at here.
Feeling like tempted ? Start by a crash course to guix.