Tag Archives: Development

Development, Electronics

USB converter woes

1 Comment

USB to rs232 converters are just never sold properly advertising what chip’s inside and right now I want to know if this one UART I’m working with perhaps is not playing fine with my existing converter cable.

I have this XScale PXA270 on a toradex-colibriboard, and it has only one full featured RS232 (FFUART) and I’m about to move things over to the lesser featured BTUART.

A theory is that my current USB converter that is based on a “Prolific PL2303” doesn’t play nicely on the serial port that isn’t a full RS232.

So I ran off and bought a new cable. I grabbed the only model I found in my local Kjell & Company store – it’s quite different looking than my existing but there’s no hint anywhere on the package or inside of it that says what chipset that empowers it.

A quick drive back home (I’m working from home in this assignment), I plugged it in and I got to see this depressingly familiar dmesg output:

usbcore: registered new interface driver usbserial
usbserial: USB Serial support registered for generic
usbcore: registered new interface driver usbserial_generic
usbserial: USB Serial Driver core
usbserial: USB Serial support registered for pl2303
pl2303 2-2.4:1.0: pl2303 converter detected
usb 2-2.4: pl2303 converter now attached to ttyUSB0
usbcore: registered new interface driver pl2303
pl2303: Prolific PL2303 USB to serial adaptor driver

So what now? I hate how (my) computers these days don’t have serial ports while the entire embedded world still very much uses them. I think I’ll go searching in my closet to see if I can find an old crap computer with a serial port to try.

Another theory is that the port simply is broken hw-wise on the dev board but that’s harder to check for me right now.

Update: it was (as usual) only my stupidity that prevented this from working. If I switch it over to the correct baudrate the usb converter does fine. But before I found that out, I did find a computer with a serial port and I did see it working on that too…

Development, Open Source

C Code Commandments

3 Comments

I’m an old school C programmers guy and I stay true to some of the older and commonly used rules present in many open source and similar projects. Since I sometimes rant about this to people, I thought I’d amuse my surrounding by stating them here for public use/ridicule. Of course heavily inspired by the great and superior The Ten Commandments for C Programmers. My commandments are not necessarily in any prio order.

Thy Code Shall Be Narrow

Only in very rare situations should code be allowed to be wider than 80 columns. I want my two or three windows next to each other horizontally and still see the code fine. Not to mention the occasional loading up in an editor in a 80 columns terminal and that is should be possibly print nicely (for reviews etc). Wide code is also harder to read I think, quite similarly to how very wide texts in web pages etc aren’t kind to your eyes either.

Thou Shall Not Use Long Symbol Names

To be able to keep the code easily readable by human eyes so that you quickly get an overview and understand things, you simply need to keep the function and variable names fairly short. Not to mention that the code gets harder to keep within 80 columns if you use ridiculously long names.

Comments Shall Be Plenty

Yes, this is something we know everyone says and few live up to. In statistical analyzes of my own C code I usually reach around 25-27% comments and I’m usually happy with that amount. Comments should explain what is otherwise not obvious in the code.

No Hiding What’s Really Happening

I’m not a fan of overloaded operators or snazzy macros that do fancy stuff without it being noticeable in the code. It should be clear when reading the code what it does. That’s also one of the reasons you don’t catch me doing a lot of C++ work…

Thou Shalt Hunt Down and Kill Compiler Warnings

Compiler warnings may be significant and in some cases they are not. Either way, it is our duty to silence them at all times. Firstly because it is often simpler to fix the code to not warn than to figure out if the warning is indeed right or not, but perhaps primarily because it makes it harder to see new warnings appearing if the old ones have been left there.

Write Portable Code Unless Forced by Evil

You may first believe that your code will live on forever on this single platform with this single compiler, but soon and very soon you will learn otherwise. Then you will cheer this rule as it makes you consider unaligned memory accesses, assuming byte-order of binary data or the size of your ‘long’ variable type.

Repeat Not, Use Functions

I see a lot of “copy and paste” programming in my daily life and I’ve learned that sooner or later such practices lead to sorrow. If you paste the same code on multiple places it not only makes it repetitive and boring to update it when an API or something changes, more seriously it increases the risk that you address bugs only on one out of many places or that the fix differ etc. It also makes the code larger and thus harder to follow and understand.

Thou Shalt Not Typedef Away Pointers

A really nasty habit to be seen in some source codes is when people use typedefs to define their own types that is simply a pointer to something. Like with ‘typedef struct whatever * whatever_t’. While I’m in general against excessive typedefing, I’m fine with them in many cases but not when used to hide pointers to look like “ordinary” types. It makes code harder to follow.

Defines, no fixed numbers

Code that relies on zero and non-zero can get away without this, but as soon as you start relying on more numbers in the code you must start using #defines or possibly enums to make them appear with names in the code. Using names is more clever than hardcoded numbers since you can avoid having to explain the number in a comment, and of course it’ll be easier to change the actual number in the code at a later point without it being a painful search-and-replace operation.

cURL and libcurl, Development

Some stats on curl development

Counting curl 6.0 and up to curl 7.19.3 we’ve done 78 releases during the 9.4 years it took.

In this time, we’ve mentioned 1259 bugfixes and 389 notable changes.

This makes one bugfix done every 2.7 days. One release done every 43rd day with an average of 16 bugfixes done in each. The longest interval ever between two curl releases was 139 days, back in 2000 when we worked to release the first version 7 release (known as 7.1).

To compare with how our work has been more recently, doing the same math limited to the 20 latest releases only (the 3.3 years since and including 7.15.0) shows that we’re still on 2.7 days per bugfix (although we know that the code base has grown steadily for years) but we’re now on 61 days between releases and 21 bugfixes/release…

All this info and more will be visible on a web page on the curl site soonish, I’m still working on polishing it up.

What other useful or useless but interesting numbers could be extracted from this?

Development, Linux, Network

10G and Direct Cache Access

6 Comments

As some of you might know, I currently work with a client doing 10G network stuff. 10G as in 10 gigabit/second Ethernet. That’s a lot of data. It’s actually so much data it’s hard to even generate network loads of this magnitude to be able to do good tests, as a typical server using SATA harddrives hardly fills a one gigabit pipe due to “slow” I/O: ordinary SATA drives don’t even reach 100MB/sec. You need RAID solutions or putting the entire thing in RAM first. So generating 10 gigabit network loads thus requires some extraordinary solutions.

Having a server that tries to “eat” a line speed 10G is a big challenge, and in fact we can’t do it as 1.25 GB/sec is just too much and yet we run a quad-core 3.00GHz Xeon thing here which is at least near the best “off-the-shelf” CPU/server you can get at the moment. Of course our software does a little bit more with the data than just receiving it as well.

Anyway, recently I’ve been experimenting with 10G cards from Myricom and when trying to maximize our performance with these beauties, I fell over the three-letter acronym DCA. Direct Cache Access. A terribly overused acronym consisting of often-used words make it hard to research and learn about! But here’s a great document describing some of the gory details:

Direct Cache Access for High Bandwidth Network I/O

Summary: it is an Intel technology for delivering data directly into the CPU’s cache, to reduce the bandwidth requirement to memory (note: it only decreases the bandwidth requirement at that moment, not the total requirement as it still needs to be read from memory into the cache, as noted in a comment below). Using this technique it should be possible to drastically reduce the time for getting the traffic. Support for this tech has been added to the Linux kernel as well since a while back.

It seems DCA is (only?) implemented in Intel’s 7300 chipset family which seems to only exist for Xeon 7300 and 7400. Too bad we don’t have one of these monsters so I haven’t been able to try this out for real yet…

Currently we can generate 10G network loads using two different approaches: one is uploading a specially crafted binary blob embedded with the FPGA image to a Xilinx-equipped board with a 10G MAC that then can do some fiddling with the packages (like increasing a counter) so that they aren’t all 100% identical. It makes a pretty good load test, even if the traffic isn’t at all shaped like the “real” traffic our product will receive. Our other approach has been even less good: upload a custom firmware to the network card and have that send the same Ethernet frame… This latter approach didn’t get better because it was a bit too complicated and badly documented on how to make a really good generator out of it. Even if I liked being able to upload custom code to my network card! 😉

Allow me to also mention that the problems with generating 10G is with small packet sizes, like 100 bytes or so as the main problem in the hardwares seem to the number of packets, not the payload part. Thus it is easier to do full line speed with 9000 bytes packets (jumbo frames) than the tiny ones we are likely to get when this product is in use by customers in the wild.

Update: this article was written in 2008. Please note that many things may have changed since then.

Development, Open Source

Open source in my day job

From people in the open source community and then especially friends and fellow hackers in projects I am involved in, I sometimes get questions on how my open source participations affect my “real job”.

I work as a consultant during the days and I do contract development for hire. I’ve been a consultant since 1996 and during this time I’ve participated in more than 25 “full-time” projects for almost as many customers.

I contribute to numerous open source projects and I’ve done it for many years. I lead and maintain several open source projects. I’ve committed many thousands of times to public source code repositories.

Does the contributions make me more attractive to potential customers? Not particularly is my rather sad experience. While some of my customers notice my track record (my CV does of course mention my most notable contributions) most of my day-job clients focus solely on other paid projects I’ve done and that exact technologies and products I worked with and created in the past. It may of course not be too strange as things I do and get paid for is then potentially “good enough for someone to pay me for” while the stuff I do for free in open source projects are… well, not paid for and thus it can’t be qualified by that ruler.

Do I get new assigments thanks to my open source projects? Yes, I do, but usually they tend to be on the smallish side and not of the bigger kinds my regular assignments at work are.

And the reality is of course also that the vast vast vaaast majority of all software consultants that people hire to do development have no public record of open source involvement so it could just be a result of that this is so rare the customers never had a reason to learn or adapt to using open source contributions as a “factor”.

Or maybe I’m just ignorant and haven’t figured out how my customers truly work.

Do I work with open source in my day job? Yes almost exclusively. I’ve been working with Linux in various embedded systems basically the last 8 years and working with Linux systems pretty much implies a wide range of open source development tools as well.

Development, Open Source

4 ohloh improvements I’d like

I am a stats junkie so I like my stats in large amounts. But I like the stats to be right and as accurate as possible, and when I look at what ohloh produces I like the concepts and ideas in general, I just think their implementation is lacking in a few vital areas that need improvement:

1. There are no dependencies or hierarchies between packages, so “I use this” counters get worthless since people mark end-user packages they use. Low-level support packages and libraries that are used indirectly don’t get many “use counts”

2. Doing very few commits in a very well used project with few authors gives you way way more points than doing a bus-load of commits in something less used with many fellow contributors. This makes the top-list of people very skewed as some of the top-64 people only did a few hundred commits ever. I doubt many mortals would consider someone who only ever did 300 commits to be a top community person. At the very moment I write this, the #1 ranked person has done 20 commits during 5 months…!

3. Too few versioning systems are supported, leaving out huge chunks of the open source world. Bazaar, mercurial and a few more are a bit too popular to be ignored without the results getting skewed.

4. I’d like to see the “number of users” of products as a percentage, as the total number of users they show include all contributors to all projects. Out of the 140,000 users (which undoubtedly include a lot of duplicates), it would surprise me if more than 10,000 have actually registered what products they use. I’ve tried to find the exact number but I failed. So 3,000 users don’t mean 3,000 out of 140,000 but 3,000 out of 10,000…

Development, Technology

Cure coming for Wrap Rage?

4 Comments

This phenomena you thought you were alone to experience, the rage and anger you feel when you’ve bought some new toy and you get it packaged in tight and nearly un-enforceable plastic that demands a decent amount of violence and persistence to crack. It’s called Wrap Rage.

I’ve been told the packages (called blister packs or clam shells) are designed to be this way to be able to show off the merchandise while at the same time prevent thefts: it is hard for a customer to just extract something out of those things in your typical physical store.

Amazon’s initiative Frustration-Free packaging is indeed a refreshing take on this and apparently an attempt to reverse this development. Online stores really cannot have any good reasons to use this kind of armor around products since there’s no risk of stealing. I wish others will follow to make the manufacturers realize that there is a market for this. This needs to be done by manufacturers of stuff, the stores cannot be made to repackage stuff due to warranties and what not.

It wouldn’t surprise me if you could even find cheaper ways to package products once you let go of some of the requirements that no longer apply for online stores. Visibility of the products once packaged is another thing that is pointless for online stores but I would expect is very important to sales in physical stores. I’ve always thought it is pretty pointless and expensive that every single package is made to be able to be a display model. To be able to attract customers to buy it. When you buy the thing online it’s no longer just pointless, it’s plain stupid.

Imagine a future when you can just open your new toy without getting bruises or scratch marks!

Development, Open Source

My million users

I’ve been working professionally with computers since 1991 and explicitly as a developer since 1993. I’ve written one or two lines of code since then. How many users could there be out there that are using something that includes my code?

Open source

I’ve participated in a wide range of open source projects, so of course all direct users of those projects would count: curl, Rockbox and let’s include subversion and others. I would guess that there are at least one million users of curl, quite likely more than so of subversion and Rockbox may also reach a million users or so. It’s of course impossible to know for sure…

Lots of open source projects use libraries that I work on now and have worked with in the past. Primarily libcurl and c-ares. Such as Boinc, git, bazaar, darcs. Millions of users, no doubt (Boinc alone has some 1.5 million users). The OLPC’s XO laptop comes with (lib)curl. I think most Linux distros these days come with curl installed. How many linux installations are there? libcurl is rather popular when used within PHP as well and there are many many million installations of PHP out there. I have code in wget, also used by millions.

Closed source users of open source I’ve participated in

Adobe acrobat reader (for non-windows platforms), Adobe’s flash player and various other Adobe products, Second life, Google Earth and others. They’re bound to have several million users. curl is included in Mac OS X.

There are also a lot of devices that use libcurl that are even harder to track: Sandisk makes mp3 players that use libcurl, Sony makes a video device that uses libcurl, Tilgin, Neuros and others make IPTV-devices that use libcurl. libcurl is used for multiple “installers” such as the one AOL provide for a specific router. There are many company users.

Closed source stuff I’ve worked with on my day-job

… is of course also used widely and all over, but me being an embedded guys I mostly work on software in products and most of the products I’ve worked within have been for various niche markets in which I have little or no knowledge about how much the products (and thus my code) are actually used. I’ve left my fingerprints on several networking products, IPTV/Digital TV settop boxes, railroad equipments, a car ignition tester, 3g/telecom switches, rfid receivers, laser-using positioning systems and more.

How many millions?

Ok, let’s for the sake of the argument say that there’s somewhere around 100 million devices with my code from me included – I really have no idea how to make a sensible estimate. Let’s for simplicity also say that there are 100 million users of these devices. I would also guess that about half of the world’s population isn’t near using devices I may have programmed. Thus, if you’re using “devices” in general there’s a probability of 3 billion/100 million = 1/30 that you’re using something that includes code that I’ve worked on…

In fact, that number is then valid for any random “device” user – if you’re reading this on my blog I don’t expect you to be very random but rather a specialized person and then I would say the likeliness of you having at least something with my code in it is almost 100% guaranteed…

Where would you say my biggest weaknesses in this reasoning are?

Development

strcasecmp in Turkish

A friendly user submitted the (lib)curl bug report #2154627 which identified a problem with our URL parser. It doesn’t treat “file://” as a known protocol if the locale in use is Turkish.

This was the beginning of a minor world-moving revelation for me. Of course this is already known to mankind and I’m just behind, but really: lots of my fellow hacker friends had no idea either.

So “file” and “FILE” are not the same word case insensitively in Turkish because ‘i’ is not the lowercase version of ‘I’.

Back to strcasecmp: POSIX pretty much makes the function useless by saying that “The results are unspecified in other locales [than POSIX]”.

I’m a bit annoyed by this fact, as now I have to introduce my own function (which thus cannot use tolower() or toupper() since they also are affected by the locale) and use since the strings in our code is clearly used for “English” strings so file and FILE truly are the same string when compared case insensitively…

Development, Open Source

popen() in pthreaded program confuses gdb

1 Comment

I just thought I’d share a lesson I learned today:

I’ve been struggling for a long time at work with a gdb problem. When I set a break-point and then single-step from that point, it sometimes (often) decides to act as if I had done ‘continue‘ and not ‘next‘. It is highly annoying and makes debugging nasty problems really awkward.

Today I searched around for the topic and after some experiments I can now confirm: if I remove all uses of popen() I no longer get the problems! I found posts that indicated that forking could confuse threaded programs, and since this program at work uses threads I could immediately identify that it uses both popen() and system() and both of them use fork() internally. (And yes, I believe my removal of popen() also removed the system() calls.)

And now I can finally debug my crappy code again to become less crappy!

My work PC runs glibc 2.6.1, gcc 4.1.3 and gdb 6.6. But I doubt the specific versions matter much.