Linux in consumer electronics

Linux is embedded in a huge number of different devices, but the high-profile gadgets – the Nokia N800 and OpenMoko phone for example – get all the attention. Those gadgets use Linux as a selling point and a differentiator, trying to appeal to developers and power users who can customize the devices to do exactly what they want. Meanwhile, the vast majority of embedded Linux devices are running it quietly. For those systems, Linux provides a stable platform, with support for a large number of architectures and devices, that just works.

Consumer electronics makers are turning to Linux in a big way. Sony provides an eye-opening list of their devices that run Linux, which covers a wide spectrum of the products that Sony makes; things like digital cameras, video cameras, televisions, audio gear, and professional video equipment. Other companies also have Linux web pages, none quite like the one that Sony provides, and the Consumer Electronics Linux Forum (CELF) has started gathering links to those sites on their embedded Linux wiki.

Linux provides a number of advantages for embedded developers, the most obvious is its price. Commercial embedded operating systems typically charge royalties on a per-device basis, which can be a significant factor, especially for low-end devices. For high-end devices, especially professional grade equipment, the cost of the OS is much less of an issue, but the Linux feature set and hardware support still make it an attractive choice.

One of the advantages that Linux provides is virtual memory – commercial embedded operating systems often rely on a flat memory layout. Virtual memory has a number of useful benefits: process isolation, shared code segments, as well as the ability to overcommit memory. Tim Bird, Sony kernel hacker and architecture group chair for CELF, puts it this way:

Another area of importance to the embedded world is the variety of hardware supported by Linux. Not only is there support for many of the CPU architectures used in embedded devices, but there are drivers for all kinds of peripherals that might be used in the design. If a driver does not exist for the specific peripheral device being used, there is probably a driver for something similar that can be used as a template for a new driver. Alternatively, the Linux Driver Project – which we covered last week – is willing to write the driver given some information about how the device operates.

Support for multiple network protocols, different bus architectures, and various peripheral connections (USB, Firewire, etc.) are also very important, depending on the intent of the device. Because the Linux community is large, and growing, it can support many more options than the commercial embedded OS vendors can. In addition, as the development staff at a consumer electronics company come up to speed on Linux, it will make sense to use it in more devices. This will lead to more supported devices, CPUs, bus architectures, network protocols, and so on.

The added features of Linux do come with a cost, which Bird refers to, of larger kernels and libraries. The linux-tiny project is an effort to reduce the size of the kernel, so-called kernel bloat, for embedded and small systems, which has been pretty well received by kernel hackers. It is a testament to the Linux developers that it already runs on everything from mainframes to mobile phones; it is a rare OS indeed that will make the effort to scale over that wide a range, with the inherent tensions between the needs of the various constituencies.

It probably isn't possible to get a shell prompt on your television or video camera, as these devices aren't meant to be user serviceable, at least at the OS level. User modifications or updates to the code may well be difficult or impossible as well. For devices that are not connected to the internet, which is presumably the case for the majority of them, this is probably a non-issue. Presumably the device manufacturers have ways of upgrading if bugs or security flaws are discovered, but those would be handled by service centers or the like. Those who are opposed to the "Tivo-ization" of the kernel will be less than pleased, but most kernel hackers seem willing to have it used that way, so long as the code is made available.

We will be seeing Linux in more places as time goes on as it is proving a robust solution for all kinds of applications. Perhaps you stare at Linux all day, hacking on code, working on graphics, or running a word processor, it is quite possible that you may also be staring at Linux at night, inside the television in your living room.