# HDL workflow
This section describes the workflow and some best practices for developing
-the Libre-SoC hardware. We use nmigen, yosys and symbiyosys, and this
+the Libre-SOC hardware. We use nmigen, yosys and symbiyosys, and this
page is intended not just to help you get set up, it is intended to
help advise you of some tricks and practices that will help you become
effective team contributors.
and formal mathematical proofs for all code at all levels is therefore
paramount.
+Therefore, we need not only to be "self-sufficient" (absolutely under no circumstances critically reliant on somebody else's servers **or protocols**) we also need to ensure that everything (including all communication such as the mailing list archives) are recorded, replicable, and accessible in perpetuity. Use of slack or a "forum" either actively prevents or makes that much harder.
+
# Collaboration resources
+The main message here: **use the right tool for the right job**.
+
+* mailing list: general communication and discussion.
+* irc channel #libre-soc: real(ish)-time communication.
+* bugtracker: task-orientated, goal-orientated *focussed* discussion.
+* ikiwiki: document store, information store, and (editable) main website
+* git repositories: code stores (**not binary or auto-generated output store**)
+* ftp server (<https://ftp.libre-soc.org/>): large (temporary,
+ auto-generated) file store.
+
+we will add an IRC channel at some point when there are enough people
+to warrant having one (and it will be publicly archived)
+
+note also the lack of a "forum" in the above list. this is very deliberate. forums are a serious distraction when it comes to technical heavily goal-orientated development. recent internet users may enjoy looking up the "AOL metoo postings" meme.
+
+note also the complete lack of "social platforms". if we wanted to tell everybody how much better each of us are than anyone else in the team, how many times we made a commit (look at me, look at me, i'm so clever), and how many times we went to the bathroom, we would have installed a social media based project "management" system.
+
## Main contact method: mailing list
To respect the transparency requirements, conversations need to be
public and archived (i.e not skype, not telegram, not discord,
and anyone seriously suggesting slack will be thrown to the
lions). Therefore we have a mailing list. Everything goes through
-there. <http://lists.libre-riscv.org/mailman/listinfo/libre-riscv-dev>
+there. <https://lists.libre-soc.org/mailman/listinfo/libre-soc-dev>
therefore please do google "mailing list etiquette" and at the very
minimum look up and understand the following:
using phone at airport flight soon, v. quick reply: ....")
* Always trim context but do not cut excessively to the point where people
cannot follow the discussion. Especially do not cut the attribution
- ("On monday xxx wrote")
+ ("On monday xxx wrote") of something that you are actually replying
+ to.
* Use inline replies i.e. reply at the point in the relevant part of
the conversation, as if you were actually having a conversation.
* Follow standard IETF reply formatting, using ">" for cascaded
the link. Which should not require any kind of login to access. ask the
listadmin if you don't have anywhere suitable: FTP access can be arranged.
+### Actionable items from mailing list
+
If discussions result in any actionable items, it is important not to
lose track of them. Create a bugreport, find the discussion in the
-archives <http://lists.libre-riscv.org/pipermail/libre-riscv-dev/>,
+archives <https://lists.libre-soc.org/pipermail/libre-soc-dev/>,
and put the link actually in the bugtracker as one of the comments.
-At some point it may become better to use <http://bugs.libre-riscv.org>
+At some point in any discussion, the sudden realisation may dawn on one
+or more people that this is an "actionable" discussion. at that point
+it may become better to use <https://bugs.libre-soc.org/>
itself to continue the discussion rather than to keep on dropping copies
of links into the bugtracker. The bugtracker sends copies of comments
*to* the list however this is 'one-way' (note from lkcl: because this
involves running an automated perl script from email, on every email,
on the server, that is a high security risk, and i'm not doing it. sorry.)
+### Mailing list != editable document store
+
Also, please do not use the mailing list as an "information or document
store or poor-man's editor". We have the wiki for that. Edit a page and
tell people what you did (summarise rather than drop the entire contents
Or, if it is more appropriate, commit a document (or source code)
into the relevant git repository then look up the link in the gitweb
source tree browser and post that (in the bugtracker or mailing list)
-See <http://git.libre-riscv.org>
+See <https://git.libre-soc.org/>
+
+### gmail "spam"ifying the list
+
+see <https://blog.kittycooper.com/2014/05/keeping-my-mailing-list-emails-out-of-gmails-spam-folder/>
+
+basically it is possible to select any message from the list, create a "filter" (under "More"),
+and, on the 2nd dialog box, click the "never send this to Spam" option.
## Bugtracker
## ikiwiki
-Runs the main libre-riscv.org site (including this page). effective,
+Runs the main libre-soc.org site (including this page). effective,
stunningly light on resources, and uses a git repository not a database.
That means it can be edited offline.
Hint: to create a new page, find a suitable page that would link to it,
first, then put the link in of the page you want to create, as if the
-page already exists. Save that page, and you will find a questionmark
+page already exists. Save that page, and you will find a question mark
next to the new link you created. click that link, and it will fire up a
"create new page" editor.
+Wiki pages are formatted in [[markdown|ikiwiki/markdown]] syntax.
+
Hint again: the wiki is backed by a git repository. Don't go overboard
but at the same time do not be afraid that you might "damage" or "lose"
pages. Although it would be a minor pain, the pages can always be
## git
-we use git. more on this below. we also use gitolite3 running on a
-dedicated server. again, it is extremely effective and low resource
-utilisation. reminder: lions are involved if github is mentioned.
+We use git. More on this below. We also use [gitolite3](https://gitolite.com/gitolite/) running on a dedicated server. again, it is extremely effective and low resource utilisation. Reminder: lions are involved if github is mentioned.
+
+[gitweb](https://git.wiki.kernel.org/index.php/Gitweb) is provided which does a decent job. <https://git.libre-soc.org/>
+
+[Git](https://en.wikipedia.org/wiki/Git) does version control, ie it tracks changes to files so that previous versions can be got back or compared.
-gitweb is provided which does a decent job. <http://git.libre-riscv.org>
+## ftp server
+
+<https://ftp.libre-soc.org/> is available for storing large files
+that do not belong in a git repository, if we have (or ever need)
+any. Images (etc.) if small and appropriate should go into the
+wiki, however .tgz archives (etc.) and, at some point, binaries,
+should be on the ftp server.
+
+Ask on the list if you have a file that belongs on the ftp server.
## server
-as an aside: all this is "old school" and run on a single core 512MB
+As an aside: all this is "old school" and run on a single core 512MB
VM with only a 20GB HDD allocation. it costs only 8 GBP per month from
mythic-beasts and means that the project is in no way dependent on anyone
else - not microsoft, not google, not facebook, not amazon.
-we tried gitlab. it didn't go well.
+we tried [gitlab](https://about.gitlab.com/). it didn't go well. please don't ask to replace the above extremely resource-efficient services with it.
# Hardware
What is particularly useful is to have hi-res screens (curved is
*strongly* recommended if the LCD is over 24in wide, to avoid eyeballs
-going "prism" through longterm use), and to have several of them: the
+going "prism" through long term use), and to have several of them: the
more the better. Either a DisplayLink UD160A (or more modern variant)
or simply using a second machine (lower spec hardware because it will
run editors) is really effective.
# Operating System
-First install and become familiar with Debian (ubuntu if you absolutely
+First install and become familiar with [Debian](https://www.debian.org/) ([Ubuntu](https://ubuntu.com/) if you absolutely
must) for standardisation cross-team and so that toolchain installation
is greatly simplified. yosys in particular warns that trying to use
Windows, BSD or MacOS will get you into a world of pain.
# editors and editing
Whilst this is often a personal choice, the fact that many editors are
-GUI based and run fullscreen with the entire right hand side *and* middle
+GUI based and run full-screen with the entire right hand side *and* middle
*and* the majority of the left side of the hi-res screen entirely unused
and bereft of text leaves experienced developers both amused and puzzled.
-At the point where such fullscreen users commit code with line lengths
+At the point where such full-screen users commit code with line lengths
well over 160 characters, that amusement quickly evaporates.
-Where the problems occur with fullscreen editor usage is when a project
+Where the problems occur with full-screen editor usage is when a project
is split into dozens if not hundreds of small files (as this one is). At
that point it becomes pretty much essential to have as many as six to
eight files open *and on-screen* at once, without overlaps i.e. not in
[[!img 2020-01-24_11-56.png size=640x ]]
(hint/tip: fvwm2 set up with "mouse-over to raise focus, rather than
-additionally requiring a mouseclick, can save a huge amount of cumulative
+additionally requiring a mouse click, can save a huge amount of cumulative
development time here, switching between editor terminal(s) and the
command terminals).
Once this becomes necessary, it it turn implies that having greater
-than 80 chars per line - and running editors fullscreen - is a severe
-hindance to an essential *and highly effective* workflow technique.
+than 80 chars per line - and running editors full-screen - is a severe
+hinderance to an essential *and highly effective* workflow technique.
Additionally, care should be taken to respect that not everyone will have
200+ column editor windows and the eyesight of a hawk. They may only have
continuously page-up and page-down to read the code even of a single
function, in full.
-This helps explain in part, below, why compliance with pep8 is enforced,
-including its 80 character limit. In short: not everyone has the same
-"modern" GUI workflow or has access to the same computing resources as
+This helps explain in part, below, why compliance with [pep8](https://pep8.org/) is enforced, including its 80 character limit. In short: not everyone has the same "modern" GUI workflow or has access to the same computing resources as
you, so please do respect that.
+More on this concept is
+[here](https://www.linuxjournal.com/content/line-length-limits).
+Note *very pointedly* that Linus Torvalds *specifically* states that
+he does not want Linux kernel development to become the exclusive
+domain of the "wealthy". That means **no** to assumptions about
+access to ultra-high resolution screens.
+
# Software prerequisites
Whilst many resources online advocate "sudo" in front of all root-level
* apt-get install build-essential
* apt-get install git python3.7 python3.7-dev python-nosetest3
* apt-get install graphviz xdot gtkwave
+* apt-get install python3-venv
+* apt-get install python-virtualenv # this is an alternative to python3-venv
* return to user prompt (ctrl-d)
-This will get you python3 and other tools that are needed. graphviz is
-essential for showing the interconnections between cells, and gtkwave
-is essential for debugging.
+This will get you python3 and other tools that are needed. [graphviz](https://graphviz.org/) is essential for showing the interconnections between cells, and [gtkwave](http://gtkwave.sourceforge.net/) is essential for debugging.
+
+If you would like to save yourself a lot more typing, check out the
+[dev-env-setup](https://git.libre-soc.org/?p=dev-env-setup.git;a=summary)
+repository, examine the scripts there and use them to automate much of
+the process below.
## git
Follow the source code (git clone) instructions here:
<http://www.clifford.at/yosys/download.html>
-Do not try to use a fixed revision (currently 0.9), nmigen is evolving
-and frequently interacts with yosys
+Or, alternatively, use the
+[yosys-et-al](https://git.libre-soc.org/?p=dev-env-setup.git;a=blob;f=yosys-et-al;hb=HEAD)
+script (which also installs symbiyosys and its dependencies)
+
+Do not try to use a fixed revision of yosys (currently 0.9), nmigen is evolving
+and frequently interacts with yosys.
+
+[Yosys](http://www.clifford.at/yosys/) is a framework for Verilog RTL.
+[Verilog](https://en.wikipedia.org/wiki/Verilog) is a hardware description language.
+RTL [Register Transfer Level](https://en.wikipedia.org/wiki/Register-transfer_level) models how data moves between [registers](https://en.wikipedia.org/wiki/Hardware_register).
## symbiyosys
the formal proof scripts will be (less resource utilisation in certain
circumstances).
+[SymbiYosys](https://symbiyosys.readthedocs.io/en/latest/) (sby) is a front-end driver program for Yosys-based formal hardware verification flows.
+
## nmigen
-nmigen may be installed as follows:
+[nmigen](https://m-labs.hk/gateware/nmigen/) may be installed as follows:
* mkdir ~/src
* cd !$
-* git clone https://github.com/m-labs/nmigen.git
+* git clone https://github.com/nmigen/nmigen.git
* cd nmigen
* sudo bash
* python3 setup.py develop
testing can then be carried out with "python3 setup.py test"
+nmigen is a Python toolbox for building complex digital hardware.
+
## Softfloat and sfpy
-These are a test suite dependency for the ieee754fpu library, and
-will be changed in the future to use Jacob's algorithmic numeric
+These are a test suite dependency for the [ieee754fpu](https://www.gaisler.com/index.php/products/ipcores/ieee754fpu) library, and
+will be changed in the future to use Jacob's [simple-soft-float](https://crates.io/crates/simple-soft-float)
library. In the meantime, sfpy can be built as follows:
git clone --recursive https://github.com/billzorn/sfpy.git
git apply /path/to/ieee754fpu/berkeley-softfloat.patch
cd ..
- # install dependencies
- python -m venv .env
- . .env/bin/activate
- pip install --upgrade -r requirements.txt
+ # prepare a virtual environment for building
+ python3 -m venv .env
+
+ # or, if you prefer the old way:
+ # virtualenv -p python3 .env
+
+ # install dependencies
+ source .env/bin/activate
+ pip3 install --upgrade -r requirements.txt
# build
- make lib -j8
+ make lib -j$(nproc)
make cython
- make inplace -j8
+ make inplace -j$(nproc)
make wheel
# install
deactivate # deactivates venv, optional
- pip install dist/sfpy*.whl
+ pip3 install dist/sfpy*.whl
You can test your installation by doing the following:
- python
+ python3
>>> from sfpy import *
>>> Posit8(1.3)
It should print out `Posit8(1.3125)`
-
+
+## qemu, cross-compilers, gdb
+
+As we are doing POWER ISA, POWER ISA compilers, toolchains and
+emulators are required.
+
+Install powerpc64 gcc:
+
+ apt-get install gcc-9-powerpc64-linux-gnu
+
+Install qemu:
+
+ apt-get install qemu-system-ppc
+
+Install gdb from source. Obtain the latest tarball, unpack it, then:
+
+ cd gdb-9.1 (or other location)
+ mkdir build
+ cd build
+ ../configure --srcdir=.. --host=x86_64-linux --target=powerpc64-linux-gnu
+ make -j$(nproc)
+ make install
+
+## power_instruction_analyzer (pia)
+
+We have a custom tool built in rust by programmerjake to help analyze
+the power instructions execution on *actual* hardware.
+
+Note: a very recent version of pip3 is required for this to work.
+
+Install rust:
+
+ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+
+Make sure we have the correct and up-to-date rust compiler (rustc):
+
+ rustup default stable
+ rustup update
+
+Use rust's package manager *cargo* to install the rust-python build tool maturin:
+
+ cargo install maturin
+
+Install from git source by doing the following:
+
+ git clone https://salsa.debian.org/Kazan-team/power-instruction-analyzer.git pia
+ cd pia
+ maturin build --cargo-extra-args=--features=python-extension
+ python3 -m pip install --user target/wheels/*.whl
+
+Note: an ongoing bug in maturin interferes with successful installation. This can be worked around by explicitly installing only the .whl files needed rather than installing everything (*.whl).
+
+## Chips4Makers JTAG
+
+As this is an actual ASIC, we do not rely on an FPGA's JTAG TAP interface, instead require a full complete independent implementation of JTAG. Staf Verhaegen has one, with a full test suite, and it is superb and well-written. The Libre-SOC version includes DMI (Debug Memory Interface):
+
+ git clone https://git.libre-soc.org/git/c4m-jtag.git/
+
+Included is an IDCODE tap point, Wishbone Master (for direct memory read and write, fully independent of the core), IOPad redirection and testing, and general purpose shift register capability for any custom use.
+
+We added a DMI to JTAG bridge in LibreSOC which is directly connected to the core, to access registers and to be able to start and stop the core and change the PC. In combination with the JTAG Wishbone interface the test ASIC can have a bootloader uploaded directly into onboard SRAM and execution begun.
+
+## Coriolis2
+
+See [[HDL_workflow/coriolis2]] page, for those people doing layout work.
# Registering for git repository access
Create a file ~/.ssh/config with the following lines:
- Host git.libre-riscv.org
+ Host git.libre-soc.org
Port 922
Wait for the Project Admin to confirm that the ssh key has been added
to the required repositories. Once confirmed, you can clone any of the
-repos at http://git.libre-riscv.org:
+repos at https://git.libre-soc.org/:
- git clone gitolite3@git.libre-riscv.org:REPONAME.git
+ git clone gitolite3@git.libre-soc.org:REPONAME.git
Alternatively, the .ssh/config can be skipped and this used:
- git clone ssh://gitolite3@git.libre-riscv.org:922/REPONAME.git
+ git clone ssh://gitolite3@git.libre-soc.org:922/REPONAME.git
# git configuration
* mkdir ~/src
* cd !$
-* git clone gitolite3@git.libre-riscv.org:soc.git
-* git clone gitolite3@git.libre-riscv.org:ieee754fpu.git
+* git clone gitolite3@git.libre-soc.org:nmutil.git
+* git clone gitolite3@git.libre-soc.org:ieee754fpu.git
+* git clone gitolite3@git.libre-soc.org:nmigen-soc.git
+* git clone gitolite3@git.libre-soc.org:soc.git
-In each of these directories, track down the setup.py file, then, as root
-(sudo bash) run the following:
+In each of these directories, in the order listed, track down the
+setup.py file, then, as root (sudo bash), run the following:
* python3 setup.py develop
for multi-user machine use however it is often just easier to get your
own machine these days.
+The reason for the order is because soc depends on ieee754fpu, and
+ieee754fpu depends on nmutil
+
If "python3 setup.py install" is used it is a pain: edit, then
install. edit, then install. It gets extremely tedious, hence why
"develop" was created.
team communication:
+* new members, add yourself to the [[about_us]] page and create yourself a home page using someone else's page as a template.
* communicate on the mailing list or the bugtracker an intent to take
responsibility for a particular task.
* assign yourself as the bug's owner
* *keep in touch* about what you are doing, and why you are doing it.
+* edit your home page regularly, particularly to track tasks so that they can be paid by NLNet.
* if you cannot do something that you have taken responsibility for,
then unless it is a dire personal emergency please say so, on-list. we
won't mind. we'll help sort it out.
as an effective organisation. It's *not* about "setting rules and meting
out punishment".
-for actual code development:
+## Coding
+
+for actual code development
+
+### Plan unit tests
* plan in advance to write not just code but a full test suite for
that code. **this is not optional**. large python projects that do not
have unit tests **FAIL** (see separate section below).
+* Prioritise writing formal proofs and a single clear unit test that is more like a "worked example".
+ We receive NLNet funds for writing formal proofs, plus they
+cover corner cases and take far less time to write
+
+### Commit tested or zero-dependent code
+
* only commit code that has been tested (or is presently unused). other
people will be depending on you, so do take care not to screw up.
not least because, as it says in the [[charter]] it will be your
responsibility to fix. that said, do not feel intimidated: ask for help
and advice, and you'll get it straight away.
+
+### Commit often
+
* commit often. several times a day, and "git push" it. this is
collaboration. if something is left even overnight uncommitted and not
pushed so that other people can see it, it is a red flag. if you find
it is making yourself a bottleneck. pair-programming is supposed to help
avoid this kind of thing however pair-programming is difficult to organise
for remote collaborative libre projects (suggestions welcomed here)
+
+### Enable editor auto-detection of file changes by external programs
+
+This is important. "git pull" will merge in changes. If you then
+arbitrarily save a file without re-loading it, you risk destroying
+other people's work.
+
+### Absolutely no auto-generated output
+
* **do not commit autogenerated output**. write a shell script and commit
that, or add a Makefile to run the command that generates the output, but
**do not** add the actual output of **any** command to the repository.
ever. this is really important. even if it is a human-readable file
rather than a binary object file.
+ it is very common to add pdfs (the result of running latex2pdf) or configure.in (the result of running automake), they are an absolute nuisance and interfere hugely with git diffs, as well as waste hard disk space *and* network bandwidth. don't do it.
+
+### Write commands that do tasks and commit those
+
* if the command needed to create any given autogenerated output is not
currently in the list of known project dependencies, first consult on
the list if it is okay to make that command become a hard dependency of
the repository and document them at the very minimum in the README,
INSTALL.txt or somewhere in a docs folder as appropriate. if unsure,
ask on the mailing list for advice.
+
+### Keep commits single-purpose
+
* edit files making minimal *single purpose* modifications (even if
it involves multiple files. Good extreme example: globally changing
a function name across an entire codebase is one purpose, one commit,
yet hundreds of files. miss out one of those files, requiring multiple
commits, and it actually becomes a nuisance).
+
+### Run unit tests prior to commits
+
* prior to committing make sure that relevant unit tests pass, or that
the change is a zero-impact addition (no unit tests fail at the minimum)
+
+### Do not break existing code
+
+* keep working code working **at all times**. find ways to ensure that this is the case. examples include writing alternative classes that replace existing functionality and adding runtime options to select between old and new code.
+
+### Small commits with relevant commit message
+
* commit no more than around 5 to 10 lines at a time, with a CLEAR message
(no "added this" or "changed that").
* if as you write you find that the commit message involves a *list* of
changes or the word "and", then STOP. do not proceed: it is a "red flag"
that the commit has not been properly broken down into separate-purpose
commits. ask for advice on-list on how to proceed.
+
+### Exceptions to small commit: atomic single purpose commit
+
* if it is essential to commit large amounts of code, ensure that it
is **not** in use **anywhere** by any other code. then make a *small*
(single purpose) followup commit which actually puts that code into use.
change which integrates untested code: just commit the new code (only)
and follow up the next day *after* running the full relevant unit tests.
-the reason for all the above is because python is a weakly typed language.
+### Why such strict rules?
+
+the reason for all the above is because python is a dynamically typed language.
make one tiny change at the base level of the class hierarchy and the
effect may be disastrous.
as a general rule, however, do not use this an an excuse to write code
first then write unit tests as an afterthought. write *less* code *in
-conjunction* with its (more basic) unit tests, instead.
+conjunction* with its (more basic) unit tests, instead. then, folliw up with
+additions and improvements.
the reason for separating out commits to single purpose only becomes
obvious (and regretted if not followed) when, months later, a mistake
commit confuses several unrelated changes, not only the diff is larger
than it should be, the reversion process becomes extremely painful.
+### PEP8 format
+
* all code needs to conform to pep8. use either pep8checker or better
run autopep8. however whenever committing whitespace changes, *make a
separate commit* with a commit message "whitespace" or "autopep8 cleanup".
you think you need greater than 80 chars, it *fundamentally* indicates
poor code design. split the code down further into smaller classes
and functions.
+
+### Docstring checker
+
* TBD there is a docstring checker. at the minimum make sure to have
an SPD license header, module header docstring, class docstring and
function docstrings on at least non-obvious functions.
+
+### Clear code commenting and docstrings
+
* make liberal but not excessive use of comments. describe a group of
lines of code, with terse but useful comments describing the purpose,
documenting any side-effects, and anything that could trip you or other
developers up. unusual coding techniques should *definitely* contain
a warning.
+
+### Only one class per module (ish)
+
* unless they are very closely related, only have one module (one class)
per file. a file only 25 lines long including imports and docstrings
is perfectly fine however don't force yourself. again, if unsure,
ask on-list.
+
+### File and Directory hierarchy
+
* *keep files short and simple*. see below as to why
* create a decent directory hierarchy but do not go mad. ask for advice
if unsure
+
+### No import star!
+
* please do not use "from module import \*". it is extremely bad practice,
causes unnecessary resource utilisation, makes code readability and
tracking extremely difficult, and results in unintended side-effects.
+
+example: often you want to find the code from which a class was imported.
+nirmally you go to the top of the file, check the imports, and you know
+exactly which file has the class because of the import path. by using
+wildcards, you have absolutely *no clue* which wildcard imported which
+class or classes.
+
+example: sometimes you may accidentally have duplicate code maintained
+in two or more places. editing one of them you find, puzzlingly, that
+the code behaves in some files with the old behaviour, but in others it
+works. after a nassive amount of investigation, you find that the working
+files happen to have a wildcard import of the newer accidental duplicate
+class **after** the wildcard import of the older class with exactly the
+same name. if you had used explicit imports, you would have spotted
+the double import of the class from two separate locations, immediately.
+
+really. don't. use. wildcards.
+
+### Keep file and variables short but clear
+
* try to keep both filenames and variable names short but not ridiculously
obtuse. an interesting compromise on imports is "from ridiculousfilename
import longsillyname as lsn", and to assign variables as well: "comb =
m.d.comb" followed by multiple "comb += nmigen_stmt" lines is a good trick
that can reduce code indentation by 6 characters without reducing clarity.
+Additionally, use comments just above an obtuse variable in order to
+help explain what it is for. In combination with keeping the the module
+itself short, other readers will not need to scroll back several pages
+in order to understand the code.
+
+Yes it is tempting to actually use the variables as
+self-explanatory-comments and generally this can be extremely good
+practice. the problem comes when the variable is so long that a function
+with several parameters csn no longer fit on a single line, and takes
+up five to ten lines rather than one or two. at that point, the length
+of the code is adversely affected and thus so is readability by forcing
+readers to scroll through reams of pages.
+
+it is a tricky balance: basically use your common sense, or just ask
+someone else, "can you understand this code?"
+
+### Reasons for code structure
+
regarding code structure: we decided to go with small modules that are
both easy to analyse, as well as fit onto a single page and be readable
when displayed as a visual graph on a full UHD monitor. this is done
* thirdly, unit testing, particularly formal proofs, is far easier on
small sections of code, and complete in a reasonable time.
+## Special warning / alert to vim users!
+
+Some time around the beginning of 2019 some bright spark decided that
+an "auto-recommend-completion-of-stuff" option would be a nice, shiny
+idea to enable by default from that point onwards.
+
+This incredibly annoying "feature" results in tabs (or spaces) being
+inserted "on your behalf" when you press return on one line, for your
+"convenience" of not needing to type lots of spaces/tabs just to get
+to the same indentation level.
+
+Of course, this "feature", if you press return on one line in edit
+mode and then press "escape", leaves a bundle-of-joy extraneous
+whitespace **exactly** where you don't want it, and didn't ask for it,
+pooped all over your file.
+
+Therefore, *please*: **before** running "git commit", get into the
+habit of always running "git diff", and at the very minimum
+speed-skim the entire diff, looking for tell-tale "red squares"
+(these show up under bash diff colour-syntax-highlighting) that
+inform you that, without your knowledge or consent, vim has
+"helpfully" inserted extraneous whitespace.
+
+Remove them **before** git committing because they are not part
+of the actual desired code-modifications, and committing them
+is a major and constant distraction for reviewers about actual
+important things like "the code that actually *usefully* was
+modified for that commit"
+
+This has the useful side-effect of ensuring that, right before
+the commit, you've got the actual diff right in front of you
+in the xterm window, on which you can base the "commit message".
+
## Unit tests
+For further reading, see the wikipedia page on
+[Test-driven Development](https://en.wikipedia.org/wiki/Test-driven_development)
+
This deserves its own special section. It is extremely important to
appreciate that without unit tests, python projects are simply unviable.
Python itself has over 25,000 individual tests.
black art. This is where team collaboration particularly kicks in,
so if you need help, ask on the mailing list.
+## Don't comment out unit tests: add them first (as failures) and fix code later
+
+Unit tests serve an additional critical purpose of keeping track of code
+that needs to be written. In many cases, you write the unit test *first*,
+despite knowing full well that the code doesn't even exist or is completely
+broken. The unit test then serves as a constant and important reminder
+to actually fix (or write) the code.
+
+Therefore, *do not* comment out unit tests just because they "don't work".
+If you absolutely must stop a unit test from running, **do not delete it**.
+Simply mark it with an appropriate
+["skip" decorator](https://docs.python.org/3/library/unittest.html#skipping-tests-and-expected-failures),
+preferably with a link to a URL in the [bugtracker](https://bugs.libre-soc.org/)
+with further details as to why the unit test should not be run.
+
# TODO Tutorials
Find appropriate tutorials for nmigen and yosys, as well as symbiyosys.
+* Robert Baruch's nmigen tutorials look really good:
+ <https://github.com/RobertBaruch/nmigen-tutorial>
* Although a verilog example this is very useful to do
<https://symbiyosys.readthedocs.io/en/latest/quickstart.html#first-step-a-simple-bmc-example>
* This tutorial looks pretty good and will get you started
* There exist several nmigen examples which are also executable
<https://github.com/m-labs/nmigen/tree/master/examples/> exactly as
described in the above tutorial (python3 filename.py -h)
+
projects / libreriscv.git / blobdiff