Re: [PATCH v2 00/12] arm64: Kconfig: Update ARCH_EXYNOS select configs

2021年9月30日(木) 18:23 Lee Jones [off-list ref]:

I've taken the liberty of cherry-picking some of the points you have
reiteratted a few times.  Hopefully I can help to address them
adequently.

On Thu, 30 Sep 2021, Krzysztof Kozlowski wrote:

quoted

Reminder: these are essential drivers and all Exynos platforms must have
them as built-in (at least till someone really tests this on multiple
setups).

quoted

Therefore I don't agree with calling it a "problem" that we select
*necessary* drivers for supported platforms. It's by design - supported
platforms should receive them without ability to remove.

quoted

The selected drivers are essential for supported platforms.

SoC specific drivers are only essential/necessary/required in
images designed to execute solely on a platform that requires them.
For a kernel image which is designed to be generic i.e. one that has
the ability to boot on vast array of platforms, the drivers simply
have to be *available*.

Forcing all H/W drivers that are only *potentially* utilised on *some*
platforms as core binary built-ins doesn't make any technical sense.
The two most important issues this causes are image size and a lack of
configurability/flexibility relating to real-world application i.e.
the one issue we already agreed upon; H/W or features that are too
new (pre-release).

Bloating a generic kernel with potentially hundreds of unnecessary
drivers that will never be executed in the vast majority of instances
doesn't achieve anything.  If we have a kernel image that has the
ability to boot on 10's of architectures which have 10's of platforms
each, that's a whole host of unused/wasted executable space.

In order for vendors to work more closely with upstream, they need the
ability to over-ride a *few* drivers to supplement them with some
functionality which they believe provides them with a competitive edge
(I think you called this "value-add" before) prior to the release of a
device.  This is a requirement that cannot be worked around.

[Chiming in as a clock driver sub-maintainer and someone who spent a
non-insignificant part of his life on SoC driver bring-up - not as a
Google employee.]

I'd argue that the proper way for them to achieve it would be to
extend the upstream frameworks and/or existing drivers with
appropriate APIs to allow their downstream modules to plug into what's
already available upstream.

Best regards,
Tomasz

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