For Android OEMs, getting a new version of the operating system onto devices can be a multi-layered endeavor fraught with peril. It’s not as easy as picking up the code from Google one afternoon, and pushing updates out the next. There is a significant amount of software development, testing, and certification to go through. Both Sony Ericsson and Motorola have released some details on the process, giving us a look at how Android gets from Google, to OEMs, to carriers, and ultimately to you.

The code drops

The whole process starts when Google drops the open source code into the Android Open Source Project (AOSP) repository. This usually happens around the time that the new Google experience device (that’s the Galaxy Nexus this time) is released. OEMs have to take that code, and integrate it with the in-house code trees to begin work. The only exception to this is the hardware partner for the official Google experience device, which gets the code early and works closely with Google. For the last two years, that was Samsung, and before that it was HTC.

The first order of business according to both companies is to start optimizing the Hardware Abstraction Layer (HAL). This is the software layer in Android that gives the software access to device hardware. In the case of Android 4.0 Ice Cream Sandwich, Google used TI OMAP as the template for the operating system so many manufacturers have to replace the HAL.

Sony Ericsson, and indeed most OEMs, rely on a fairly consistent hardware design across a range of products. Chips are usually sourced from the same makers, and the internals reuse many smaller parts. Sony Ericsson uses Qualcomm’s Snapdragon processors in phones, so a new HAL is required. At least its consistent design saves some time and will allow the company to update all 2011 phones.

Motorola is currently straddling both Tegra and OMAP-based products, so its task could be more complicated. The newer OMAP devices like the Droid Razr and Bionic could get preferential treatment because of easier development. In fact, Motorola’s OMAP devices are the only products it has confirmed will get Android 4.0. Users of the Photon 4G or Droid X2 could have a longer wait on their hands.

All OEMs also have to contend with small differences in various other hardware modules like audio, WiFi, and Bluetooth. The HAL will need changes on a per-device basis taking into account different form factors, screen sizes, and specs, too.

Next page: Tweaking and testing