Re: "Pseudo-DIA" between the Linux Kernel Development Community and its Users - 2/5 We're talking about an Operating System here

Lukas Bulwahn

I agree. At the time the system developer decides to use the operating system,
the operating system developer has already finished testing. The process is
more like the selection process for a hardware component. The customer can
assess the testing that the supplier has already done and do its own testing to
evaluate alternative components.

This process isn't particularly foreseen in the safety standards. That being said,
we're talking about the general functionality in this e-mail, not the safety
Yes, I agree. There is a step of interpretation from what the safety standards expects vs. how the whole development and integration act.

What 26262 says, in 20262-8 Clause 12 is that the organization should prepare
a specification for the component, including the requirements on the
component. The organization must then provide evidence the requirements
have been tested to an adequate coverage level and that the component is
valid for its intended use by verification according to clause 9.

The process for deriving the specification and requirements is not described
and I assume that the component should be treated like any component
created by bespoke development, i.e. in the architecture and design phases of

Nicolas Mc Guire addressed this in his 61508-based approach, especially
noting that when other factors are relatively equal, one criteria for selection
between alternative components could be their certifiabliity; their systematic
capability. That's one of the uses for Annex QR.

That is the implicit DIA here. Then the operating system supplier
executes an own "development process" down to the implementation (with
his own V model process).
Either we misunderstand each other or I disagree. At the point that the
customer uses the operating system, as in using it in its architecture and design
phase, the operating system already exists and should be completely
I think the issue is that:

We both acknowledge that there is an own development process down to the implementation and a (partial) one for verification & validation.
The main result of that process is the kernel source code. But, we expect another "supporting result" wrt. quality assurance/management that describes which activities have been performed how well. Let us call that a "process quality report" for now.

Side note: Of course, at the moment, this process quality report does not exist for the kernel as a structured and collective description (you would need to know and search various sources etc. to get something in that direction).

But let us assume it would exist:

I think you now make thoughts along those lines: the process quality report would describe its scope of covered activities and hence, the downstream integrator would simply need to close all further gaps after understanding the scope. (So, no Pseudo-DIA required.)
I was thinking along those lines: There is one document, a Pseudo-DIA, that defines the interface between the kernel community and downstream integrator (for any previous work the community has done), and with that at hand, we have a clear understanding what need to described in a process quality report, as the scope is defined now.

Does this resolve the misunderstanding?

I am happy to say no DIA is involved, but the process quality report has (amongst many other content) a defined scope according to a certain development process description. That would cover the concern I was trying to resolve with this Pseudo-DIA here at this process interface between community and downstream integrator.

The only DIA I see here, is the DIA I discussed below, where the user
community issues a generic DIA that the operating system developer can
consider during further development. Considering that I said that the OS has
already been developed in this scenario, the OS has been developed based on
the requirements, including any customer requirements, that the OS
developer gathered in its requirement phase.
Okay. I will try to resolve that below.

And longer question:
So, does the operating system supplier or the system developer test
the operating system?
(I have an assumption here and there is again a certain split of the
activities in this
Both do testing. The operating system supplier can, of course, integrate the OS
in its test harnesses, or representative test user systems, before release. The
system developer does acceptance and validation testing in its development
But where is this assumption documented? If that assumption is crucial for quality assurance, which I believe it is, this point would need to a common agreement and details need documentation. A Pseudo-DIA could offer a structured form of documenting that.

I hope that everyone agree that this point needs to cover by our discussion and presentation in some way. Anyone disagrees?

I think a process description should cover these insights above from
you, and the assumed responsibilities here.

(If this is part of a DIA or some even more basic overview document on
the process is secondary to me; we will figure it out while

It is clear though (even if we do not have the description) that we
certainly need to have the common understanding, e.g., as you
described the overall process above, and one core aspect of it is "who
does what". Otherwise, this mapping of ISO clauses/QM standards
(ASPICE and such) to described activities is hardly to understand.
Off the top of my head, I don't know what the implications are for supplier
management. I could imagine that acceptance test development is covered
there as well.
Maybe that is where the testing of the downstream integrator side lands. Just that you know: The split of testing is tricky, that why I did not like that example for the initial email on pseudo DIA.

A discussion of a proper description and mapping on its own, let us remember and shift that to a later point. As I said, it is tricky point for a process perspective.

As we see in this discussion, already on the higher levels, we assume
multiple "V- model like development process" happening in some
interweaved and temporally decoupled way.
Like I said, I think that component development has finished before the system
developer starts. What is happening, especially with Linux, is that, after a
version is released, the version continues to be updated with bug-fixes. That,
for me, is part of the maintenance process, the quality of which could be a
criteria in the component selection process.

Documenting that as if it is "one V-model process" will probably
distort the whole process assessment and that has impact on results
(at least, in comprehensibility, and maybe even in the risk assessment).

There is of course, the possibility that the system developer needs
custom OS functionality, a new feature (or, to use Chris Temple's
terminology, a
In which case, if the system developer can afford it, either party
can develop the feature or enhancement from scratch. Consider what
Google has done with off-tree development of Linux functionality for
Android, which they sometimes got retroactively accepted upstream.
In this case, Google would be making a DIA with itself: between its
Android and Linux organisations, which is foreseen in the definition of a
Agree. I consider this a completely new and different development
process, that needs a DIA in itself.

An organization making a DIA with itself is the default. Usually, the
organization using Linux will act internally and as part of the
community. That does not invalidate the idea of a DIA. Still
activities in the community are different than the activities that are
done internally, and in the end, the quality statement comes from
understanding how well both activities (internally, and in the community
with others) work, and how well they "work together" (interact, are aligned,

While a system developer must choose an operating system from the
flavours and versions that are available at the time, what ELISA is
actually looking at is the interaction between the user community
and the Linux development community. The user community has the
possibility to specify its expectations on future operating system
development: a DIA for future functionality in general rather than
for a specific feature development effort. The operating system
developers then have the possibility of considering the needs of the
community when adding or modifying OS features.
Agree. That is the upfront development to the development process above.

Summarizing, we identified three "development processes":

1. Understanding the system needs and selecting and configuring the
operating system appropriately. Result: kernel build configuration

2. Previous development process of the operating system (without any
involvement of the own organization)
Result: source code (relevant here to the system integrator is the
source code for kernel build configuration above)

3. Specific development process of the operating system (with
involvement of the own organization and a clear goal towards a
specific quality level)
Result: New features specifically driven by extensions of 1.

Again, 2. And 3. Intersect but it help in the discussion to separate those.

Do you agree to "all" above?
Yes, there are these 3 development processes, whereby 1) does not involve
operating system development would not involve a DIA between an individual
user and the OS developer.
Yes, but there is an interface between the downstream integrator and the kernel community (between 1. and 2.&3.). Is a DIA needed for that or something else? (See discussion above).

If we resolved the one point above, we have enough material to document this email thread in report form, and see where it fits into the description of a reference process.


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