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.

Manufacturer/phone/SoC =>	LG/G3/Qcom	Samsung/Galaxy 4/Exynos	Acer/E3/Mediatek	Asus/Zenfone 6/Atom	Huawei/P6/Hisilicon	Sony/Z3/Qcom
Kernel area
Mach specific	417411	89118	?	?	?	393767
Media	131811	163540	?	1466714	153032	124973
Video	221550	176787	37876	38785	238267	214027
Wireless	110946	123308	387214	91449	122501	81502
Sound	216643	86127	12932	74057	19250	213137
Input	107334	51160	2752	53321	35410	62930
Camera	66989	1342	7900	1024348	51065	56744
GPU	53345	172300	114932	36545	198323	53468
Power	61912	7635	94059	66629	45127	46173
USB	99295	35366	30795	34074	121075	98663
Notable other	Prima - 565210	firmware - 101069		i2c - 105744	reg - 90034

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 ALSO is not suitable for modem audio)
• userspace (mini-distro?) for testing
• suspend-to-ram