Version 3.1 of the Linux kernel was the first release to include regmap support and only included a bare minimum of features in order to ease review so version 3.2 has been a pretty big one for regmap development with some pretty major features being built on top of the core code. Support for register [...]
Recently I’ve been noticing a surprising pattern in code I’m reviewing for the kernel. A lot of people seem to have taken to writing code that I’d expect to look like this: switch (thing) { case VALUE: /* Stuff */ break; case BAR: /* Nonsense */ break; default: /* Whatever */ break; } with if [...]
A good proportion of I2C and SPI device drivers in the kernel contain some very similar code for accessing the register maps of hardware connected to those buses – most hardware designers have solved the problem of providing very similar ways. Linux 3.1 introduces a new kernel API called regmap which factors out this code [...]
Linux 3.0 was released today – another fairly quiet release for the ASoC core, plus the usual collection of new drivers: Support DAPM controls that affect multiple paths – mainly used for single register bits that affect the routing for a stereo pair of audio streams. Simplifications in the cache infrastructure. New machine drivers for [...]
One of the biggest differences between working on most other OSs and working upstream on drivers for the Linux kernel is that elsewhere the core is usually a fixed thing that has been released and can’t really be changed, even if source is available (which may not even be the case). If whatever subsystem you’re [...]
Building the kernel for the Nexus S is straightforward – the kernel is public as one would expect so it’s simply a matter of building it using the standard Linux build system (the machine is called herring in the code). There is one gotcha, though – the driver for the BCM4329 WiFi controller is a [...]
Kernel 2.6.38 will add support for tracing ASoC using trace points. Previously all logging for ASoC had been done using printk(), meaning that changing the active logging required a kernel rebuild and that when trace was enabled the volume of trace could easily become very disruptive to other logging within the system. Trace points solve these [...]
2.6.37, which was released today, has been a very big release for ASoC – about 40,000 lines of changes covering every single file within the subsystem plus a bunch of new drivers. The highlights are: Overhaul of the core APIs for registration of all kinds of devices from my co-maintainer Liam Girdwood, reducing the level of [...]
Linux 2.6.35 has been a fairly interesting release from an ASoC point of view, with several notable framework enhancements: Support for keeping audio paths through the CODEC up during system suspend, primarily intended for use with devices where the Linux system is one of several independent systems running on the device and the other systems [...]
Linux 2.6.34 was released today. This contains a fairly substantial batch of ASoC updates, including: Support for turning CODEC biases off completely when idle, providing power savings for modern devices with ground referenced outputs where this can be done quickly at runtime without pops and clicks. Support for disabling physical writes to the device in [...]