LWN.net Weekly Edition for March 22, 2012

Fedora mulls ARM as a primary architecture

The ARM architecture is growing in popularity and is expected to expand its reach beyond the mobile and "small embedded" device space that it currently occupies. Over the next few years, we are likely to see ARM servers and, potentially, desktops. Fedora has had at least some ARM support for the last few years, but always as a secondary architecture (SA), which meant that the support lagged that of the two primary architectures (32 and 64-bit x86) of the distribution. Recently, though, there has been discussion of "elevating" ARM to a primary architecture (PA), but, so far, there is lots of resistance to a move like that.

The subject came up at a meeting of the Fedora engineering steering committee (FESCo) on March 19. Adding ARM as a primary architecture for Fedora 18 was a late addition to the agenda, which annoyed some, but the discussion was largely to "start the ball rolling and collect feedback from everyone", as Kevin Fenzi put it. There will be many other opportunities to discuss the idea, he said. The meeting log bears that out as the only vote taken (or even proposed) was to ask for input from various teams (QA, release engineering, kernel, and infrastructure) about the impact of a change like that.

The difference between primary and secondary architectures for Fedora is rather large. Releases cannot be made without all of the packages building and working for each primary architecture, whereas secondary architecture packages can languish. In fact, the current release of Fedora for ARM is based on Fedora 14—though there are alphas of Fedora 15 and 17—which is past its end-of-life on x86.

The meeting discussion focused mostly on the motivation for making ARM a PA and why the project's goals couldn't be met, at least for now, by remaining as an SA. Much of the motivation, it would seem, is for Fedora to get out ahead of the curve on ARM support. Making ARM a "first class citizen" would increase its visibility and put the full weight of the Fedora community behind the effort. Therein, it seems, lies part of the problem.

One could argue that Fedora has already fallen behind the curve with respect to ARM given what Ubuntu and Debian are doing to support the architecture. There is a lot going on with Linux on ARM, and Fedora may well find itself becoming less relevant if support for ARM does not improve. But the question seems to be whether that support needs to improve as an SA before even considering whether it can be a new PA.

Based on the discussion in the meeting, Matthew Garrett posted an RFC draft of the requirements to promote an architecture to a PA. So far, there has been no architecture that has transitioned from an SA to a PA, so some kind of ground rules need to be established. Garrett lists seven potential criteria, prefaced by:

Much of the response to that posting concerns the amount of time it (currently) takes to build ARM packages (vs. the time for x86 and other architectures). Jakub Jelinek noted that GCC builds for 64-bit x86 are on the order of two hours, while building for ARM takes much longer. He followed that up with actual numbers from GCC 4.7 builds for Fedora 17, which ranged from one-and-a-half hours for x86_64 to more than 26 hours for armv5tel (and more than 24 for armv7hl). Brendan Conoboy pointed out that plans for newer "enterprise hardware" would cut those ARM build times in half, but that still leaves a substantial gap.

Slow builds are not just an annoyance, as there are some impacts for the distribution if package building takes "too long". Josh Boyer lists two. If a package builds for the x86 family, but then fails to build for ARM, the x86 build will have to be resubmitted after the ARM problem is fixed. In addition, when trying to do an update (for a security issue for example), it has to wait for the slowest build to finish before the update can go out. Adam Williamson also notes another problem that could arise in the release verification process:

Build speed is a technical issue that can presumably be overcome (eventually) with faster hardware. Other possibilities like cross-compiling on faster x86_64 servers or parallelizing the Koji build system (perhaps using something like distcc) seem to have been ruled out by Fedora release engineering or the Fedora ARM team. While some remain unconvinced, Conoboy is adamant that cross-compilation is not a good solution:

But some question the wisdom of even having criteria for promoting SAs to PAs, whether it makes sense for Fedora to even consider ARM for a PA, or both. Kevin Kofler is definitely in the last category as he believes that the current list of PAs "should be set in stone unless a MAJOR change in hardware landscape happens". Some would argue that the change is already happening. But he is concerned that additional PAs put a burden on all of the package maintainers, so that it should require an extraordinary event (like "x86 gets discontinued by the hardware manufacturers and everyone uses ARM instead") before any change like that is even considered. He continues:

Kofler harps on the same points throughout the thread, belittling the ARM market share (at least in the market segments that he thinks should be targeted) and finding the build times for ARM packages to be untenable. He considers the large existing base of ARM devices to be unsuitable for installing Fedora, at least at this point. But, as Richard W.M. Jones points out, that is changing rapidly:

Others were also skeptical of the current ARM hardware being a good target for Fedora, but Williamson points out that getting Fedora ARM running does more than just target those devices. The ARM project is looking toward the future, both on servers and mobile devices. Getting the distribution running on one is a big step toward having it available for the other.

But the speed of the build system is just one symptom of the problems that another PA will bring. One of the bigger questions, which remains largely unanswered as yet, is what making ARM a PA would do for Fedora as a distribution. It's reasonably clear why it would help the Fedora ARM project to have ARM as a primary, but the advantages to the distribution, at least at this point, are less clear. As Garrett put it:

Peter Jones Robinson outlined many of the advantages that the Fedora ARM team sees in another fedora-devel thread. Essentially, it would spread the load of responsibility throughout the Fedora community. That is, of course, the underlying concern of many posters in the threads. But Jones sees it this way:

There is, of course, nothing stopping the ARM team from achieving most of its goals while staying as secondary architecture. It will be more difficult and likely require more volunteers, but the Fedora project as a whole needs to be convinced of the advantages of taking on the "burden" of ARM as a primary. So far, the ARM project doesn't seem to have made a convincing case for that, but, given the importance of the architecture going forward, one might guess that the situation may change in the next year or two. In the meantime, setting some goal posts for any secondary architecture that wants to be promoted seems like a good first step.

Comments (60 posted)

Mozilla reconsiders H.264

Mozilla raised eyebrows in mid-March when a patch materialized that would allow Gecko to fall back on operating system or hardware media decoders for multimedia content — in particular for patent- and royalty-encumbered codecs like H.264, which are not supported natively in Gecko. The project had fought hard to promote the adoption of unencumbered alternatives (such as Ogg Theora or Google's WebM), so many on the mozilla.dev.platform discussion group saw enabling any support for H.264 as a violation of principle. Mozilla's Chief Technology Officer Brendan Eich argued, however, that the decision is an improvement over the existing Flash-fallback method, that Mozilla has more important fights to focus on, and that the blame for WebM's snail-paced adoption lies squarely at the feet of Google.

History of the WebM, part 1

Eich posted his take on the situation in a round-up at his own blog (which was then syndicated at the official Mozilla Hacks blog), which started with a history lesson on H.264, WebM, and the HTML5 <video> element. As far back as 2007, Eich and Mozilla had argued for the standardization of the <video> and <audio> elements to include "unencumbered" baseline codecs — at the time, Ogg Vorbis for audio and Ogg Theora for video. Eich argued that the term "unencumbered" most accurately describes the state of the codecs needed to ensure that the open web remains open; the issue is not about open source (for there are open source implementations of encumbered codecs), nor is it about patents (for standards bodies can and will accepted a patented codec if the patent holders agree to license it under royalty-free terms).

In 2007's <video> element fight, the main opponent of Theora was H.264, which was being pushed by a royalty-collecting consortium of companies. The protracted battle ultimately resulted in a non-decision, with the default codec language being removed from the draft standard. But the situation appeared to take a sudden shift in favor of unencumbered codecs in 2009, when Google purchased codec-maker On2 and released the WebM codec under unencumbered terms.

WebM was far newer than Theora and offered quality roughly on par with H.264; Theora's relative performance was a big reason Google did not advocate it as the default codec.. Google subsequently announced its intention to transcode YouTube videos to WebM, and in 2010 Adobe announced that it would support WebM in its Flash products (meaning not just the browser plug-ins, but the content-creation tools and media-delivery servers as well). In January 2011, Google went a step further, and publicly announced that it would drop support for H.264 from its Chrome browser.

But that change never happened. 14 months later, Chrome still supports H.264, and Eich and other Mozilla employees report that Google has remained silent about the decision when asked. Adobe didn't implement the WebM support that it promised either.

Meanwhile, Eich said, H.264 adoption has continued to spread, which has hampered Firefox's growth. For starters, Google's oft-cited promise to trancode YouTube's content to WebM is not all it is cracked up to be: to date Google has only transcoded half of the site's videos, and more importantly, YouTube only delivers WebM content to desktops, and only for those videos that serve no ads (which Eich said makes up a shrinking portion of the total). No other major sites have rejected H.264 in favor of WebM delivery either, while the consumer electronics industry builds more and more H.264 encoding support into video cameras.

On the desktop, Firefox falls back on the Flash plug-in's H.264 support, but on mobile devices, there is no such option. Mozilla believes that mobile browsers are clearly the battlefield deserving the most attention, and on top of that, the project's Boot to Gecko (B2G) effort stands no chance of making it into device-makers' products without H.264 support, Eich said.

Patches and a new API

The combination of Google not pushing WebM and content creators adopting H.264 puts Mozilla in an untenable position, Eich said. Yet the majority of phone and tablet designs ship with a pre-authorized (meaning the royalty fees have been paid) H.264 decoder in silicon, which is what led developer Andreas Gal to propose letting Gecko hand H.264 decoding (and perhaps other encumbered formats like MP3 and AAC) down to the OS or hardware level. Although other option have been discussed, Eich endorses Gal's solution. The upshot is that Firefox and B2G users will be able to see H.264 content on platforms that support it, Mozilla will not have to pay royalty fees (or pass them on to users), and the project can turn its attention to fighting for unencumbered codecs in the next round of standardization battles.

Those battles are not far off, Eich said, starting with the WebRTC real-time chat standard — which is already in-progress and looks poised to recommend unencumbered codecs. There will be other fights, he said, and other generations of video streaming codecs. Continuing to ignore H.264, particularly on mobile devices, would ultimately risk making Mozilla irrelevant further down the line, if not nonexistent altogether:

Gal's patch is attached to bug 714408. In essence, it creates a new API (which Gal dubbed the Media Player API, or MPAPI) for use by OS or hardware decoders. On desktop OSes like Linux, MPAPI would likely be tied in to a media framework like GStreamer (which can use encumbered codecs). It is also possible that the Mozilla Flash plug-in could continue to serve as the H.264 decoding chain on desktop systems, which would require work to expose MPAPI to the Gecko's main plug-in API, NPAPI. Of course, Adobe has also said that it will stop developing its NPAPI Flash plug-in for Linux, which means Flash-fallback will not remain a solution for free OSes in the long term.

As of now, the patch itself is the main source of information on MPAPI, which is still very much a work in progress. MPAPI would hand audio and video frames back to the main Gecko rendering toolchain, however, meaning the content would be fully integrated with the page's JavaScript, HTML, and CSS like any other <video> or <audio> element. The vast majority of the energy expended about the move has not been with its technical points, but with whether or not Mozilla's decision itself is wise, foolish, too pessimistic, or long overdue.

Reaction

The mozilla.dev.platform discussion thread about Gal's proposal is rife with critics arguing that Mozilla is making the wrong move, and with defenders inside and outside the project. The criticisms fall into three basic camps: those that think the H.264 situation is not as bad as described, those that feel Mozilla has not tried hard enough to advocate WebM (or that it should try Just One More Time), and those that object to enabling any form of H.264 playback on principle alone.

Critics who say that WebM has not lost to H.264 tend to point to Google's YouTube transcoding effort (which Eich countered in his blog post), or hold out hope that Google will indeed drop H.264 support from Chrome (often based on the number of WebM "supporters" listed). On the latter point, Eich argues that Chrome's H.264 support is moot, because the desktop browser would simply fall back on the Flash plug-in like Firefox does today. In fact, he said, Chrome's heavily optimized Flash plug-in amounts to a "practically custom" Flash offering "best-of-breed fallback".

Christopher Blizzard added that ultimately, the content-delivery sites simply are not interested in WebM:

Justin Lebar typified the position that Mozilla is giving up too quickly, calling it "going down without a fight," and saying that he would:

Side-stepping the fact that Lebar's public deadline idea paradoxically threatens to increase support for H.264 if it is not abandoned, Mozilla's Robert O'Callahan calls it "grossly unfair" to suggest that Mozilla has not fought hard enough or long enough against H.264 adoption:

Likewise, Asa Dotzler confirmed that Mozilla has spent months trying to get a response from Google on the H.264 support question, only to be met with silence. O'Callahan also observed that there is already mobile hardware capable of decoding WebM video, but that Google does not enable it on Android devices. In the absence of support from the format's owners, Mozilla says, it alone cannot move WebM forward.

The objection on principle is trickier. Some in the discussion thread expressed personal hurt that Mozilla was not standing its ground against H.264 playback support, but more were concerned that relenting would make it harder for the organization to lobby against encumbered formats in the future. Eich argued that anyone who ignores the fact that Firefox users watch H.264 video via the Flash plug-in is "hiding behind Mother Adobe's skirts" and is not taking a "realistic view of the entire fallback logic chain, and of Firefox's current acute dependency on Flash", which is not different in kind from falling back on an OS decoder. Gal concurred, noting that the MPAPI proposal is only "using existing accelerated decoders that already are licensed and available on the system."

Regarding Mozilla's ability to advocate for open and unencumbered formats in the future, Doztler said that the project has backed down on other lost battles in past, such as the document.all DOM feature, but has maintained it credibility. Mozilla can influence the web, and from time to time kill a bad idea, he said in another message, but "sometimes the Web decides to go where we don't want it;" not supporting it only costs the project developers and users.

Ultimately, though, Dotzler argues that even in light of H.264's popularity, Mozilla's WebM advocacy does not constitute a wasted effort:

A continuing story

It is worth remembering that however one feels about the H.264 lobby and its royalty-collecting schemes, the presence of dedicated video decoding chips is hardly an isolated situation. There are currently a great many components in our computers which are covered by patents, and many chips for which we do not have source code. Yet enabling software access to those components is not perceived as a violation of principle. Furthermore, it is hard to argue that the Flash plug-in that Firefox currently falls back on is turf worth fighting for — it has a history of bugs and security holes unrelated to the video decoders it ships.

The debate over enabling H.264 playback via MPAPI shows little sign of calming down. Eich, Dotzler, Gal, and the other project members continue to argue that enabling the format is a purely pragmatic move, and that it would be a better use of Mozilla's energy to combat encumbered codecs on the still-in-development format battles.

They got a boost on March 18 when Mozilla chief Mitchell Baker posted her own blog entry in support of the proposed change. Baker said that "giving our users a great experience" is both one of the project's key values, and a demanding goal that drives realistic product development.

The comment thread on Baker's blog follows much the same pattern as the discussion group. There are supporters, commiserators, and vocal critics. But wherever H.264 itself ends up on future versions of Firefox and B2G, one thing is for sure: H.264-vs-WebM is not the last codec fight the software world will see. As several in the thread pointed out, progress on H.265 is already well underway, and the players involved are similar — there can be little doubt that the battle will be similar, too.

Comments (25 posted)

The N9: what MeeGo could have been

The N9 is an attractive device, only slightly larger than a Nexus One. The spouse, upon handling it, complained about the rather sharp corners - but proved reluctant to hand the device back anyway. The corners do stand out in an age when everything is supposed to be rounded, and they can dig into the palm slightly, but it's all a matter of taste. The handset's specifications are reasonably standard for this vintage of device; there is a 1GHz processor, 1GB of RAM, and 16GB of storage. In a welcome change from previous Nokia devices, the N9 uses a standard micro-USB connector instead of something special Nokia made up for that specific handset. The camera is quite nice; there is also a front-facing camera, though the built-in Skype client is unable to use it. By all appearances, the handset is sealed forevermore; replacing the battery does not appear to be an option.

Android users will have likely gotten used to that environment's home screen which can be populated (especially with CyanogenMod builds) with a wide variety of application launchers, contact shortcuts, active widgets, and more. The N9 MeeGo experience is somewhat different, in that there are three specialized home screens with limited potential for customization. The first of these is the familiar matrix of icons providing access to applications on the phone. Users can rearrange the icons (including putting them into subfolders), but there is no way to put anything other than application launchers on this screen.

It is also possible to remove applications via this screen. Dishearteningly, one quickly learns that, as with many Android builds, some applications have been rendered immortal and unremovable. Your editor has little use for Facebook or Twitter applications, but they cannot be made to go away. The best that can be done is to move them to a folder where, at least, they can be kept out of sight.

The second "home" screen (accessible via a left or right swipe across the screen) shows the running applications in a 2x2 grid. Their current screens are visible, and specific applications can be killed if desired. As one might expect, tapping on an application's screen brings it back to the foreground. The third screen is a notification area; messages, weather information, and the latest urgent Twitter spam will show up here.

Annoyingly, none of the home screens rotate when the phone is held in the landscape orientation. Applications handle rotation without trouble, but the home screens appear to be special.

The applications shipped with the phone are generally attractive and nice to use - though sometimes they seem to get into dead end screens where a "back" button would be nice to have. There is a mapping and navigation application that works nicely and comes with suitably annoying voices in a wide range of languages. The camera application is feature-rich and responsive. There is a central account manager that organizes access credentials; interestingly, it can hook into Google, but not for contact information. Getting access to contacts will be one of the first things a former Android user will want to do; fortunately it is possible by telling the phone that Google is an Exchange server. WiFi tethering is built into the phone but "forbidden" for US users; fortunately, one can install the "SpotOn" application to get around that bit of obnoxiousness.

On the other hand, the web browser makes one wish for the Android equivalent. Android's browser has a "fit page to screen" option that does a nice job of rendering the interesting part of a web page in an optimally readable form; the MeeGo browser, instead, just mashes the entire page, unreadably, onto the screen, requiring zoom-in gestures and side-to-side scrolling for almost every page that has not been specifically designed for small screens. That Android feature, arguably, is on its own responsible for the fact that nobody at LWN has found the time to make a more mobile-friendly version of the site; the N9 has made it clear that not everybody has as good an experience.

The MeeGo on-screen keyboard, while being entirely functional, is also not as nice as the Android equivalent. There appears to be no built-in spelling correction or word prediction, making typing a longer and more error-prone process. That is one of the bigger shortcomings of this system. Typing on keyboard-less handsets is a painful enough procedure even with a top-quality on-screen keyboard; this is not the place for a second-rate solution. (Correction: there is a simple prediction mechanism that only seems to appear some of the time; it is better than nothing, but doesn't change the main point of this paragraph).

There is, naturally, an applications store full of things to add on to an N9. A number of important programs are there, and, inevitably, the handset comes with Angry Birds already installed. The range of available applications falls far short of that found in the Android store, though. That is far from surprising; given that MeeGo was a lame-duck platform from the beginning, there will be little motivation for developers to put any time into supporting it.

Inside the device

The MeeGo system is a far more Linux-like environment than Android provides. A terminal application comes preinstalled on the device; it works well enough for what it is, but the truth of the matter is that trying to do command-line work with an on-screen keyboard is always going to be painful. Fortunately, there's an easier way. If one puts the device into developer mode (a simple menu tweak) and plugs it into a computer's USB port, the device offers to connect in "SDK mode." In that mode, it presents as a network interface; there is even a built-in DHCP server so the computer side of the connection gets configured automatically. After that, it's just a matter of using SSH to obtain a shell on the handset. Unlike Android handsets, the N9 has Busybox on it from the start, so the shell is actually reasonably usable.

For the most part, the phone environment feels like Linux. There is, however, no functioning su command; one is, instead, supposed to use devel-su. The result is a shell that claims to be root, but all it takes is a find command run from the top of the filesystem to see that root is not all-powerful on this system. There are certain things that one still cannot access or change. This behavior is the result of the MeeGo security framework in action. Through a combination of trusted computing techniques and mandatory access control, Nokia keeps the device locked down at a certain level. It wouldn't do, after all, to let those pesky users have direct access to the media files that they think they bought on their handset.

Of course, keeping the users away is not the only motivation for the security framework; it is also intended to prevent applications from acting against the users' interests. Applications are installed with "resource tokens" describing the actions they are allowed to carry out; they include the ability to query location information, access the camera, make calls, etc. Superficially it looks a lot like the Android permissions mechanism, but the implementation appears to be wired more deeply in at the kernel level.

Notably, the application installer does not expose resource tokens to the user, so there is no way to know what types of access a given application will have - a major difference from Android. One suspects that most Android users never look at the list of requested permissions, but a subset of us tend to examine them closely indeed. The inability to know what access has been granted to an application seems like a major shortcoming. That will be doubly true anywhere outside of a strict walled-garden application repository; on this system, applications from outside Nokia's store, if they can be installed at all, can only have a restricted set of permissions. But, restricted or not, the user should have the chance to review the permissions requested by an application.

What if you want to bypass the mandatory access control and truly have full access to the device? The answer would appear to be a tool called INCEPTION. It allows the installation of applications with full privilege; one can also disable the security framework altogether. Your editor has not had the time to play with this tool, but it appears to be the ticket for those who are eager to void their warranties and reach for full control of the handset.

Perhaps a true measure of the freedom of a piece of hardware is the existence of independent operating system distributions for it. In the Android world, there is CyanogenMod along with a long list of less well-known, often more dubious, "mods." For the N9 the alternatives on offer are somewhat more restricted, but those who are truly adventurous can give NemoN9 a try. Nemo is the current incarnation of the "Mer" project; it is trying to continue the development of the MeeGo framework as an independent effort. Unfortunately, activity in this project seems to have slowed considerably, though it is still producing regular releases and its use in the upcoming Vivaldi tablet may spur development in the future. What releases Nemo has made have not found their way over to NemoN9, though, which was last updated in November, 2011.

The end of the line

Your editor has often said in the past that MeeGo could become a credible challenger to Android and a strong force in the mobile world in general. After some hands-on experience with a MeeGo device, that impression has not changed. MeeGo provides a polished and pleasant user experience. It falls short of current Android releases in some ways, but it is much nicer to use than the early Android-based devices were. With a bit of work, MeeGo could have been a truly competitive - and more community-friendly - alternative. The fact that things did not turn out that way is a sad comment on the state of the market and the management of certain companies.

The good news is that the developers who worked on this system are out there; many of them are still employed at Nokia. MeeGo may even see some further development for devices other than handsets. But the sad fact is that Nokia has placed its bets on a proprietary operating system with uncertain prospects in the mobile market. If that bet does not work out as hoped, Nokia may yet rediscover the high-quality, free-software alternative at its disposal. Then, perhaps, we'll see a new attempt to put MeeGo-based handsets on the market. For now, though, the N9 has all the look of a solid, sleek and polished platform with no future. In truth, it deserved better than that.

Comments (85 posted)