Kernel areas of focus for mainlining

This page has a list of areas of the kernel where multiple SoCs have code out-of-tree, or that appear to need some work in order to accommodate contribution of device-related software.

= Overview = The following table shows major out-of-tree areas of code, for mobile phone products based on the 3.4 Linux kernel. Although this kernel is quite old, it was the one currently shipping in phones in late 2014 and early 2015, when this analysis was done. It demonstrates the major technical areas where vendors used out-of-tree kernel code, for that generation of products.

The table shows different phones, and the number of lines they have out-of-mainline for several different kernel areas. The analysis was done using the upstream-analysis-tools (See https://github.com/tbird20d/upstream-analysis-tools). Since this task was mostly automated, the results here should not be considered definitive. That is, most of the categorization of diffs was done using regex matches on the file paths. Although this can result in some mis-categorizations of diffs, the results appear to show general patterns which may be of interest.

Note that the table shows the number of insertions (or changes). The number of deletions was found to be inconsequential for this analysis.

= Technical areas = Here are some lists of things to get mainlined, in different technical areas:

USB

 * USB-gadget to charger interface
 * Currently in progress at Linaro.
 * Code for external vbus and ID detection (looks like extcon was created for stuff like this - ish, it's mainly a mainlining of the Android switch API though it probably does fit)

= Notes from ksummit-discuss list =
 * RGB leds - not the same as 3 leds, and sometimes have hardware acceleration
 * battery over-discharge protection
 * charger (there are 3 different chargers on N900)
 * voice link to modem (Nokia says ALSA is not suitable for modem audio)
 * No need for this, ALSA is in active use for rather a lot of production phones...
 * userspace (mini-distro?) for testing
 * suspend-to-ram