Technical Blog of Richard Hughes

Ambient light sensors let us change the laptop panel brightness so that you can still see your screen when it’s sunny outside, but we can dim it when the ambient room light level is lower to save power.

I’ve spent a bit of time over the last few months designing a small OpenHardware USB device that acts as a ambient light sensor. It’s basically an uncalibrated ColorHug1 design with a less powerful processor, but speaking a subset of same protocol so all the firmware update and test tools just work out of the box.

The sensor itself is a very small (12x22mm) printed circuit board that inserts directly into a spare USB socket. It only sticks out about 9mm from the edge of the laptop as most of the PCB actually gets pushed into the USB slot.

ColorHugALS can currently control the backlight when running the colorhug-backlight utility. The Up/Down header buttons do the same as the hardware BrightnessUp and BrightnessDown keys. You can still set the absolute backlight so you’re in control of the absolute level right now, the ALS modifying the level either side of what you just set in the coming minutes. The brightness is modified using a exponential moving average, which makes the brightness changes smooth and unnoticeable on hardware with enough brightness levels.

We also use the brightness value at start to be what you consider “normal” so the algorithm tries to stay out of the way. When we’ve got some defaults that work well and has been tested the aim is to push this into gnome-control-center and gnome-settings-daemon for GNOME 3.18 so that no additional software is required.

I’ve got 42 devices in stock now. Buy one here!

A few weeks ago Christian asked me to help with the firmware update task that a couple of people at Red Hat have been working on for the last few months. Peter has got fwupdate to the point where we can “upload” sample .cap files onto the flash chips, but this isn’t particularly safe, or easy to do. What we want for Fedora and RHEL is to be able to either install a .rpm file for a BIOS update (if the firmware is re-distributable), or to get notified about it in GNOME Software where it can be downloaded from the upstream vendor. If we’re showing it in a UI, we also want some well written update descriptions, telling the user about what’s fixed in the firmware update and why they should update. Above all else, we want to be able to update firmware safely offline without causing any damage to the system.

So, lets back up a bit. What do we actually need? A binary firmware blob isn’t so useful, and so Microsoft have decided we should all package it up in a .cab file (a bit like a .zip file) along with a .inf file that describes the update in more detail. Parsing .inf files isn’t so hard in Linux as we can fix them up to be valid and open them as a standard key file. The .inf file gives us the hardware ID of what the firmware is referring to, as well as a vendor and a short (!) update description. So far the update descriptions have been less than awesome “update firmware” so we also need some way of fixing up the update descriptions to be suitable to show the user.

AppStream, again, to the rescue. I’m going to ask nice upstreams like Intel and the weird guy who does ColorHug to start shipping a MetaInfo file alongside the .inf file in the firmware .cab file. This means we can have fully localized update descriptions, along with all the usual things you’d expect from an update, e.g. the upstream vendor, the licensing information, etc. Of course, a lot of vendors are not going to care about good descriptions, and won’t be interested in shipping another 16k file in the update just for Linux users. For that, we can actually “inject” a replacement MetaInfo file when we curate the AppStream metadata. This allows us to download all the .cab files we care about, but are not allowed to redistribute, run the appstream-builder on them, then package up just the XML metadata which can be consumed by pretty much any distribution. Ideally vendors would do this long term, bu you need got master versions of basically everything to generate the file, so it’s somewhat of a big ask at the moment.

So, we’ve now got a big blob of metadata we can read in GNOME Software, and show to Fedora users. We can show it in the updates panel, just like a normal update, we just can’t do anything with it. We also don’t know if the firmware update we know about is valid for the hardware we’re running on. These are both solved by the new fwupd project that I’ve been hacking on for a few days. This exit-on-idle daemon allows normal users to apply firmware to devices (with appropriate PolicyKit checks, typically the root password) in a safe way. We check the .cab file is valid, is for the right hardware, and then apply the update to be flashed on next reboot.

A lot of people don’t have UEFI hardware that’s capable of using capsule firmware updates, so I’ve also added a ColorHug provider, which predictably also lets you update the firmware on your ColorHug device. It’s a lot lower risk testing all this super-new code with a £20 EEPROM device than your nice shiny expensive prototype hardware from Intel.

At the moment there’s not a lot to test, we still need to connect up the low level fwupdate code with the fwupd provider, but that will be a lot easier when we get all the prerequisites into Fedora. What’s left to do now is to write a plugin for GNOME Software so it can communicate with fwupd, and to write the required hooks so we can get the firmware upgrade status as a notification for boot+2. I’m also happy to accept patches for other hardware that supports updates, although the internal API isn’t 100% stable yet. This is probably quite interesting for phones and tablets, so I’d be really happy if this gets used on other non-Fedora, or non-desktop usecases.

Comments welcome. No screenshots yet, but coming soon.

To save someone else a wasted evening, RA4 on the MicroChip PIC 16F1454 is an input-only pin, not I/O like stated in the datasheet. In other news, I’ve prototyped the ColorHug ALS on a breadboard (which, it turns out was a good idea!) and the PCB is now even smaller. 12x19mm is about as small as I can go…

An ambient light sensor is a little light-to-frequency chip that you’ve certainly got in your tablet, most probably in your phone and you might even have one in your laptop if you’re lucky. Ambient light sensors let us change the panel brightness in small ways so that you can still see your screen when it’s sunny outside, but we can dim it down when the ambient room light is lower to save power. Lots of power.

There is a chicken and egg problem here. Not many laptops have ambient light sensors; some do, but driver support is spotty and they might not work, or work but return values with some unknown absolute scale. As hardware support is so bad, we’ve not got any software that actually uses the ALS hardware effectively, and so most ALS hardware goes unused. Most people don’t actually have any kind of ALS at all, even on high-end models like Thinkpads

So, what do we do? I spent a bit of time over the last few weeks designing a small OpenHardware USB device that acts as a ALS sensor. It’s basically a ColorHug1 with a much less powerful processor, but speaking the same protocol so all the firmware update and test tools just work out of the box. It sleeps between readings too, so only consumes a tiiiiny amount of power. I figure that with hardware that we know works out of the box, we can get developers working on (and testing!) the software integration without spending hours and hours compiling kernels and looking at DSDTs. I was planning to send out devices for free to GNOME developers wanting to hack on ALS stuff with me, and sell the devices for perhaps $20 to everyone else just to cover costs.

The device would be a small PCB, 12x22mm in size which would be left in a spare USB slot. It only sticks out about 9mm from the edge of the laptop as most of the PCB actually gets pushed into the USB slot. It’s obviously non-ideal, and non-sexy, but I really think this is the way to break the chicken/egg problem we have with ALS sensors. It obviously costs money to make a device like this, and the smallest batch possible is about 60 – so before I spend any more of my spare money/time on this, is anyone actually interested in saving tons of power using an ALS sensor and dimming the display? Comment here or email me if you’re interested. Thanks.

I’ve been using F3 to check my flash drives, and this is how I discovered my drives were counterfeit. It seems to me this kind of feature needs to be built inside gnome-multi-writer itself to avoid sending fake flash out to customers. Last night I wrote a simple tool called gnome-multi-writer-probe which does the following few things:

* Reads the existing data from the drive in 32kb chunks every 32Mbish into RAM
* Writes random blocks of 32kb every 32MBish, and also stores in RAM
* Resets the drive
* Reads all the 32k blocks from slightly different addresses and sizes and compares them to the random data in RAM
* Writes all the saved data back to the drive.

I only takes a few seconds on most drives. It also tries to be paranoid, and saves the data back to the drive the best it can when it encounters an error. That said, please don’t use this tool on any drives that have important data on them; assume you’ll have to reformat them after using this tool. Also, it’s probably a really good idea to unmount any drives before you try this.

If you’ve got access to gnome-multi-writer from git (either from jhbuild, or from my repo) then please could you try this:

sudo gnome-multi-writer-probe /dev/sdX

Where sdX is the USB drive you want to test. I’d be interested of the output, and especially interested if you have any fake flash media you can test this with. Either leave a comment here, grab me on IRC or send me an email. Thanks.

tl;dr Don’t use promo-newa.com, they are scammers that sell fake flash.

Longer version: For the ColorHug project we buy a lot of the custom parts direct from China at a fraction of the price available to us in the UK, even with import tax considered. It would be impossible to produce such a low cost device and still make enough money to make it worth giving up our evenings and weekends. This often means sending thousands of dollars to sketchy-looking companies willing to take on small (to them!) custom orders of a few thousand parts.

So far we’ve been very lucky, until last week. I ordered 1000 customized 1GB flash drives to use as a LiveUSB image rather than using a LiveCD. I checked out the company as usual, and ordered a sample. The sample came back good quality, with 1GB of fast flash. Payment in full was sent, which isn’t unusual for my other suppliers in China.

Fast forward a few weeks. 1000 USB drives arrived, which look great. Great, until you start using them with GNOME MultiWriter, which kept throwing validation warnings. Using the awesome F3 and a few remove-insert cylces later, the f3probe tool told me the flash chip was fake, reporting the capacity to be 1GB, when it was actually 96Mb looped around 10 times.

Taking the drives apart you could also see the chip itself was different from the sample, and the plastic molding and metal retaining tray was a lower quality. I contacted the seller, who said he would speak to the factory later that day. The seller got back to me today, and told me that the factory has produced “B quality drives” and basically, that I got what I paid for. For another 1600USD they would send me the 1GB ICs, which I would have to switch in the USB units. Fool me once, shame on you; fool me twice, shame on me.

I suppose people can use the tiny flash drives to get the .icc profile off the LiveCD image, which was always a stumbling block for some people, but basically the drives are worthless to me as LiveUSB devices. I’m still undecided whether to include them in the ColorHug box; i.e. is a free 96Mb drive better than them all going into landfill?

As this is China, I understand all my money is gone. The company listing is gone from Alibaba, so there’s not a lot I can do there. So other people can hopefully avoid this same mistake, I’ve listed all the details here, which hopefully will become googleable:

Promo-Newa Electronic Limited(Shenzhen)
Wei and Ping Group Limited(Hongkong)  

Office: Building A, HuaQiang Garden, North HuaQiang Road, Futian district, Shenzhen China, 0755-3631 4600
Factory: Building 4, DengXinKeng Industrial Zone, JiHua Road,LongGang District, Shenzhen, China
Registered Address: 15/B—15/F Cheuk Nang Plaza 250 Hennessy Road, HongKong
Email: sales@promo-newa.com
Skype: promonewa

Joshua from Plugable sent me 4 different USB hubs this week so they could be added as quirks to gnome-multi-writer. If you’re going to be writing lots of USB drives, the Plugable USB3 hubs now work really well. I’ve got a feeling that inserting and removing the drive is going to be slower than the actual writing and verifying now…

I’ve been talking to various people about the update descriptions we show to the user. Without exception, the messages we show to end users are really bad. For example, the overly-complex-but-not-actually-useful:

Or, the even more-to-the-point:

Update to 3.15.4

I’m guilty of both myself. Why is this? Typically this text is written an over-worked and under-paid packager doing updates to many applications and packages. Sometimes the packager might be the upstream maintainer, or at least involved in the project, but many times it’s just some random person that got fingered to maintain a particular package. This doesn’t make an awesome person to write beautiful prose and text that thousands of end users are going to read. It also doesn’t make sense to write the same beautiful prose again and again for every distribution out there.

So, what do we need? We need a person who probably wrote the code, or at least signed it off, who cares about the project and cares about the user experience. i.e. the upstream maintainer.

What I’m proposing is that we ask upstream maintainers to write the release information in a way that can be shown in the software center. NEWS files are not stanardized, and you don’t typically have a NEWS file for each application in your upstream tarball, so we need something else.

Suprise suprise, it’s AppStream to the rescue. AppStream has a <release> object that fits the bill almost completely; you can put upstream version information and long (optionally translated) formatted descriptions.

Of course, you don’t want to write both NEWS and the various appdata files at release time, as that just increased the workload of the overly-busy upstream maintainer. In this case we can use appstream-util appdata-to-news in the buildsystem and generate the former from the latter automatically. We’re outputting markdown for the NEWS file, which seems to be a fairly good approximation of what NEWS files actually look like at least for GNOME.

For a real-world example, see the GNOME MultiWriter example commit that uses this.

There are several problems with this approach. One is that the translators might have to translate lots more text; and the obvious solution to that seems to be to only mark strings to be translated for stable versions. Alas, projects like GNOME don’t allow any new strings in stable versions, so we’ll either have to come up with an except for release notes ammendment to that, or just say that all the release notes are only ever available in C locale.

The huge thing to take away from this blog, if you are intending to use this new feature is that update descriptions have to be understandable by end users. Various bug fixes is not helpful, but Fixes a crash when adding a joystick is. End users neither care or understand Use libgusb rather than libusbx and technical details that do not affect the UI or UX of the application should be omitted.

This doesn’t work for distribution releases, e.g. 3.14.1-1 to 3.14.1-2, but typically these are not huge changes that we need to show so prominently to the user.

I’m also writing a news-to-appdata.py script, so if anyone wants to take the plunge on an existing project it might be good to wait for that unless you like lots of copy and pasting.

Comments, as always, welcome.

When you do a search in GNOME Software it returns any result of any application with AppStream metadata and with a package name it can resolve in any remote repository. This works really well for software you’re installing from the main distribution repos, but less well for some other common cases.

Lets say I want to install Google Chrome so that my 2 year old daughter can ring me on hangouts, and tell me that dinner is ready. Lets search for Chrome on my Fedora Rawhide system.

Whoa! Wait, how did you do that? First, this exists in /etc/yum.repos.d/google-chrome.repo — the important line being enabled_metadata=1. This means “download just the metadata even when enabled=0” and means we can get information about what packages are available in repos we are not enabling by default for legal or policy reasons.

[google-chrome]
name=google-chrome
baseurl=http://dl.google.com/linux/chrome/rpm/stable/x86_64
enabled=0
gpgcheck=1
repo_gpgcheck=1
enabled_metadata=1
gpgkey=https://dl-ssl.google.com/linux/linux_signing_key.pub

We’ve also got a little XML document with the AppStream metadata (just the long description and keywords) called /usr/share/app-info/xmls/google-chrome.xml which could be included in the usual vendor-supplied fedora-22.xml if that’s what we want to do.

The other awesome feature this unlocks is when we have addon repos that are not enabled by default. For instance, my utopia repo full of super new free software applications could be included in Fedora, and if the user types in the search word we ask if the repo should be enabled. This would solve a lot of use cases if we could ship .repo files for a few popular COPRs of stuff we don’t (yet) ship in Fedora, but are otherwise free and open source software.

All the components to do this are upstream in Fedora 22 (you need a new librepo, libhif, PackageKit, libappstream-glib and gnome-software, phew!) although I’m sure we’ll be tweaking the UI and UX before Fedora 22 is released. Comments welcome.

 

I’ve just released GNOME MultiWriter 3.15.2, which is the first release that makes it pretty much feature complete for me.

Reads and writes are now spread over root hubs to increase throughput. If you’ve got a hub with more than 7 ports and the port numbers don’t match the decals on the device please contact me for more instructions.

In this release I’ve also added the ability to completely wipe a drive (write the image, then NULs to pad it out to the size of the media) and made that and the verification step optional. We also now show a warning dialog to the user the very first time the application is used, and some global progress in the title bar so you can see the total read and write throughput of the application.

With this release I’ve now moved the source to git.gnome.org and will do future releases to ftp.gnome.org like all the other GNOME modules. If you see something obviously broken and you have GNOME commit access, please just jump in and fix it. The translators have done a wonderful job using transifex, but now I’m leaving the just-as-awesome GNOME translator teams handle localisation.

If you’ve got a few minutes, and want to try it out, you can clone the git repo or install a package for Fedora.

Richard