This document discusses the benefits of contributing device drivers and other code to the Linux kernel upstream first instead of maintaining private branches. It outlines Chrome OS's strategy of picking long-term stable kernels and contributing hardware support to upstream. While challenging, working upstream provides many benefits like free code reviews, bugfixes, and easier updates. The document shows that Chrome OS contributions have helped increase upstream support for vendors' devices and that there is still work remaining to upstream GPU and other drivers. It demos mainlining the Samsung Chromebook Plus by using the open source Panfrost GPU driver instead of a vendor driver.

1. Driving the industry
toward upstream first
Enric Balletbo i Serra, Collabora Ltd.

2. 2
About me

3. 3
Photo by Artem Beliaikin from Pexels

4. 4
Agenda
Upstream is challenging
Chrome OS
Mainline on Chromebooks

5. 5
Working upstream is challenging . . .
●
Time and commitment
●
Many stakeholders
●
Discussions

6. 6
. . . but has multiple benefits
●
Quality impact
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Less maintenance
●
Less regressions

7. 7
Agenda
Upstream is challenging
Chrome OS
Mainline on Chromebooks

8. 8
Chrome OS
●
Security is important
●
Chrome OS devices auto-update every ~6 weeks
●
Devices are supported for ~6 years
●
Lots of different devices in the field
Impossible to maintain a kernel
for every device

9. 9
Chrome OS kernel
●
Pick LTS kernel every year
• All devices that year use that kernel
• 6–7 branches but not 50
●
Switch to a newer kernel version at least once during
device lifetime

10. 10
Doug Anderson, Chrome OS developer at ELC NA 2019
~10 years ago there was much angst about”
Android doing all private development”
Chrome OS” tries to not replicate that”

11. 11
Upstream First

12. 12
Chrome OS kernel tags
[UPSTREAM]
[FROMGIT]
[FROMLIST]

13. 13
Chrome OS kernel tags
[BACKPORT]
[FIXUP]
[CHROMIUM]

14. 14
Why upstream is good for Chrome OS
●
“Free code reviews”
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“Free bugfixes”
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Makes uprevs possible“ ”
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Makes the system more solid
●
Starting the next project is easier

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Chrome OS - UPSTREAM commits
chromeos-4.4 chromeos-4.14 chromeos-4.19
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Chrome OS – CHROMIUM commits
chromeos-4.4 chromeos-4.14 chromeos-4.19
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Why Chrome OS is good for upstream
●
Provides review bandwidth upstream
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Merges upstream patches and thus provides extra testing
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Requires HW vendors to work with upstream

18. 18
Contributions by vendor: Mediatek
v3.10
v3.12
v3.14
v3.16
v3.18
v4.0
v4.2
v4.4
v4.6
v4.8
v4.10
v4.12
v4.14
v4.16
v4.18
v4.20
v5.1
v5.3
0
50
100
150
200
250
300

19. 19
Contributions by vendor: Rockchip
v3.10
v3.12
v3.14
v3.16
v3.18
v4.0
v4.2
v4.4
v4.6
v4.8
v4.10
v4.12
v4.14
v4.16
v4.18
v4.20
v5.1
v5.3
0
50
100
150
200
250
300

20. 20
Agenda
Upstream is challenging
Chrome OS
Mainline on Chromebooks

21. 21
What’s the
CrOS EC?
Chrome OS Embedded Controller
Chromebook motherbooard

22. 22
Chrome OS Embedded Controller
Application
Processor
EC
PD
Accelerometer
Barometer
Light
Backlight (PWM)
Keyboard
Lightbar
RTC

23. 23
The PAST
The CrOS EC upstream effort
●
The upstream process consisted on:
• Squash downstream patches
• Split properly between subsystems
• Test the patches with a specific
device
• Submit the patch to the subsystem
ML

24. 24
The PAST
The CrOS EC upstream effort
●
The problems:
• Driver rework
• The abuse of the MFD API subsystem
• Test on a specific device

25. 25
The PRESENT
The CrOS EC upstream effort
●
Most CrOS EC drivers are now upstream
●
New related drivers will go through the
upstream first path
●
Some patches needs some rework

26. 26
What’s still missing in mainline?
drivers/gpu/
drivers/net/
drivers/media/
drivers/pinctrl/
drivers/platform/
other
drivers/
gpu 49.00 %
net 24.30 %
media 1.40 %
pinctrl 1.00 %
platform 0.90 %
other 23.40 %
4.19 LTS / chromeos-4.19

27. 27
What’s missing in drivers/gpu?
midgard
amd
i915
msm
gpu-other
other
drivers/gpu
midgard 9.70 %
amd 31.30 %
i915 1.40 %
msm 1.90 %
gpu-other 2.10 %

28. 28
The Open-source GPU drivers effort
●
~10% of the differences are unlikely to
be upstreamed
●
There were no good open-source
alternative

29. 29
The Open-source GPU drivers effort
●
We have now Panfrost
●
Can Chromebooks use Panfrost?

30. 30
Demo

31. 31
Samsung
Chromebook Plus

32. 32
Samsung
Chromebook Plus

33. 33
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