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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 1 Oct 2021 14:00:47 +0200
Message-ID: <CAK8P3a1HtDoEDeqs42s1hDzCZMwU7MhudJ7TVONn6TjoijaWRw@mail.gmail.com>
Subject: Re: [PATCH v2 00/12] arm64: Kconfig: Update ARCH_EXYNOS select configs
To:     Saravana Kannan <saravanak@google.com>
Cc:     Olof Johansson <olof@lixom.net>,
        Will McVicker <willmcvicker@google.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Sylwester Nawrocki <s.nawrocki@samsung.com>,
        Tomasz Figa <tomasz.figa@gmail.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Alessandro Zummo <a.zummo@towertech.it>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        John Stultz <john.stultz@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Lee Jones <lee.jones@linaro.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
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        Linux ARM <linux-arm-kernel@lists.infradead.org>,
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        linux-clk <linux-clk@vger.kernel.org>,
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        linux-rtc@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>
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On Fri, Oct 1, 2021 at 8:02 AM Saravana Kannan <saravanak@google.com> wrote:

> > A much more valuable approach would be to work towards being able to
> > free up memory by un-probed drivers at the end of boot. That would
> > possibly benefit all platforms on all architectures.
>
> Sure it would help memory after boot, but it won't help with size on
> "disk", kernel load time, etc. And some of the devices have very tight
> boot requirements. Think battery operated outdoor cameras for example.

I think we can draw a clear line (or several lines) between devices that boot
from strictly constrained NOR flash and those that run a platform-independent
kernel.

Also, when I look at a distro kernel, I see over 5000 kernel modules that
need to be stored on disk, but only a small fraction of those are platform
specific while most are for general-purpose pluggable devices, network
features or file systems that could be used on any system.

The vmlinux file is clearly too big and includes too much stuff that should
be in loadable modules, but I'm not really that worried about disk space
for the platform specific code.

         Arnd