Skip to main content

Posts

Building and using coverage-instrumented programs with Go

tl;dr We can create coverage-instrumented binaries, run them and aggregate the coverage data from running both the program and the unit tests.

In the Go world, unit testing is tightly integrated with the go tool chain. Write some unit tests, run go test and tell anyone that will listen that you really hope to never have to deal with a build system for the rest of your life.

Since Go 1.2 (Dec. 2013), go test has supported test coverage analysis: with the ‑cover option it will tell you how much of the code is being exercised by the unit tests.

So far, so good.

I've been wanting to do something slightly different for some time though. Imagine you have a command line tool. I'd like to be able to run that tool with different options and inputs, check that everything is OK (using something like bats) and gather coverage data from those runs. Even better, wouldn't be neat to merge the coverage from the unit tests with the one from those program runs and have an aggregated view of …
Recent posts

Testing for pending migrations in Django

DB migration support has been added in Django 1.7+, superseding South. More specifically, it's possible to automatically generate migrations steps when one or more changes in the application models are detected. Definitely a nice feature!

I've written a small generic unit-test that one should be able to drop into the tests directory of any Django project and that checks there's no pending migrations, ie. if the models are correctly in sync with the migrations declared in the application. Handy to check nobody has forgotten to git add the migration file or that an innocent looking change in models.py doesn't need a migration step generated. Enjoy!

See the code on djangosnippets or as a github gist!

Continuous Testing with Patchwork

As promised in the post introducing my recent work on Patchwork, I've written some more in-depth documentation to explain how to hook testing to Patchwork. I've also realized that a blog post might not be the best place to put that documentation and opted to put it in the proper manual:

http://patchwork-freedesktop.readthedocs.org/en/latest/testing.html
Happy reading!

Augmenting mailing-lists with Patchwork - Another try

The mailing-list problem
Many software projects use mailing-lists, which usually means mailman, not only for discussions around that project, but also for code contributions. A lot of open source projects work that way, including the one I interact with the most, the Linux kernel. A contributor sends patches to a mailing list, these days using git send-email, and waits for feedback or for his/her patches to be picked up for inclusion if fortunate enough.

Problem is, mailing-lists are awful for code contribution.

A few of the issues at hand:
Dealing with patches and emails can be daunting for new contributors,There's no feedback that someone will look into the patch at some point,There's no tracking of which patch has been processed (eg. included into the tree). A shocking number of patches are just dropped as a direct consequence,There's no way to add metadata to a submission. For instance, we can't assign a reviewer from a pool of people working on the project. As a re…

Working in a separate prefix

I've been surprised in the past to discover that even some seasoned engineers didn't know how to use the autotools prefix feature. A sign they've been lucky enough and didn't have to deal with Autotools too much. Here's my attempt to provide some introduction to ./configure --prefix.

Working with or in "a separate prefix" is working with libraries and binaries (well, anything produced by 'make install' in an autotooled project really) installed in a different directory than the system-wide ones (/usr or even /usr/local that can become quite messy). It is the preferred way to hack on a full stack without polluting your base distribution and has several advantages:
One can hack on the whole stack without the fear of not being able to run your desktop environment you're working with if something goes wrong,More often than not, one needs a relatively recent library that your distribution doesn't ship with (say a recent libdrm). When working wit…

git commit --fixup and git rebase -i --autosquash

It's not unusual that I need to fix previous commits up when working  on a branch or in the review phase. Until now I used a regular commit with some special marker to remember which commit to squash it with and then git rebase -i to reorder the patches and squash the fixup commits with their corresponding "parent" commits.

Turns out, git can handle quite a few of those manual manipulations for you. git commit --fixup <commit> allows you to commit work, marking it as a fixup of a previous commit. git rebase -i --autosquash will then present the usual git rebase -i screen but with the fixup commits moved just after their parents and ready to be squashed without any extra manipulation.

For instance, I had a couple of changes to a commit buried 100 patches away from HEAD (yes, a big topic branch!):
$ git diff diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 29f3813..08ea851 100644 --- a/drivers/gpu/drm/i915/intel_display.c …

HDMI stereo 3D & KMS

If everything goes according to plan, KMS in linux 3.13 should have stereo 3D support. Should one be interested in scanning out a stereo frame buffer to a 3D capable HDMI sink, here's a rough description of how those modes are exposed to user space and how to use them.

A reader not well acquainted with the DRM sub-system and its mode setting API (Aka Kernel Mode Setting, KMS) could start by watching the first part of Laurent Pinchart'sAnatomy of an Embedded KMS Driver or read David Herrmann's heavily documented mode setting example code.

Stereo modes work by sending a left eye and right eye picture per frame to the monitor. It's then up to the monitor to use those 2 pictures to display a 3D frame and the technology there varies.

There are different ways to organise the 2 pictures inside a bigger frame buffer. For HDMI, those layouts are described in the HDMI 1.4 specification. Provided you give them your contact details, it's possible to download the stereo 3D par…