October 6, 2016 - Javier Martinez Canillas

Samsung OSG Contributions to Linux Kernel 4.8

Linux 4.8 was released on September 25, and in this release the Samsung Open Source Group (OSG) contributed 432 patches that modified 110,741 lines of code. Although 4 engineers contributed to different Kernel subsystems, almost all of these changes comes from Mauro Carvalho Chehab’s work to improve the media subsystem documentation.

One noteworthy news item in this release is that another OSG member has been honored with a maintainer role, now that Luis de Bethencourt is taking maintainership of the BeFS filesystem. Javier Martinez Canillas is now listed as a reviewer for the Samsung Exynos ARM architecture.

The following list is all of the OSG engineers that contributed to this release and the number of changesets and lines of code, as reported by Jonathan Corbet and Greg Kroah-Hartman’s gitdm tool.

OSG developers by changesets
Mauro Carvalho Chehab 347 80.3%
Javier Martinez Canillas 69 16.0%
Shuah Khan 11 2.5%
Luis de Bethencourt 5 1.2%
OSG developers by changed lines
Mauro Carvalho Chehab 110741 99.4%
Shuah Khan 343 0.3%
Javier Martinez Canillas 292 0.3%
Luis de Bethencourt 36 0.0%

OSG Contributions to This Release

For this release, Mauro worked mostly on converting the media documentation from the DocBook format to the Sphinx doc format. Besides that work, he did cleanups on different media drivers, troubleshooted and fixed several digital TV drivers that were either not working anymore or not properly reporting the signal quality measurements. Finally, he fixed a race condition during media device nodes unregistration, which lead to a nasty use-after-free bug.

Shuah also worked to fix the race conditions between ioctl calls and media device unregistration. This was caused by an incorrect lifetime management of embedded data structures on the media core. To detect these kind of regressions earlier, she also added new media device node tests to the kselftests framework. Last but not least, she fixed several bugs in the s5p-mfc driver and improved error messages on the exynos-drm driver.

Javier worked to improve the support for Exynos machines, by fixing several bugs that prevented the s5p-mfc driver to work with GStreamer, a bug that prevented to Suspend-to-RAM, cleanups for the mwifiex driver and enabling media drivers in the Exynos default configs. He also did some enhancements to the media documentation and fixed device tree compiler warnings for different device tree source files.

Luis fixed issues on the wilc1000, wilc1000 and iio accel drivers. He also fixed a build error cause by kernel.h including dynamic_debug.h even when it wasn’t dynamic debug directly.

The Impact of the OSG

According to LWN’s report for v4.8 contributions, Samsung contributed a total of 637 patches that changed 120693 lines of code. This means that 54% of Samsung total patches and 92% of modified lines came from Mauro alone. That’s an impressive number for a single person so isn’t a surprise that Mauro is listed as the top contributor for 4.8, both by changesets and changed lines.

The merge window for v4.9 is currently open and OSG patches are already being merged for the next release. We’ll provide a more detailed update of this work after Linux 4.9 is released.

Javier Martinez Canillas

About Javier Martinez Canillas

Javier was a Senior Linux Kernel Developer for the Samsung Open Source Group. He has contributed to different kernel subsystems with a focus on ARM and Exynos SoC support. Besides hacking, he enjoys spending as much time as possible with his wife Tami and their twins, running, reading and writing technical articles like "Kbuild: the Linux Kernel Build System", published by the Linux Journal.

Image Credits: OSDC

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