linux-kernel - Re: [PATCH 0/2] i2c: tegra: allow compiling out support for Tegra's special constrollers

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Date:   Sun, 16 Jan 2022 21:34:42 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH 0/2] i2c: tegra: allow compiling out support for Tegra's
 special constrollers

16.01.2022 21:03, Michał Mirosław пишет:
> On Sun, Jan 16, 2022 at 08:54:08PM +0300, Dmitry Osipenko wrote:
>> 16.01.2022 19:02, Michał Mirosław пишет:
>>> To patches that, combined, reduce I2C driver's code by ~2kB and a bit
>>> from runtime overhead for non-Tegra20 or non-Tegra210 builds.
>>>
>>> Michał Mirosław (2):
>>>   i2c: tegra: allow DVC support to be compiled out
>>>   i2c: tegra: allow VI support to be compiled out
>>>
>>>  drivers/i2c/busses/Kconfig     | 16 ++++++++++++++++
>>>  drivers/i2c/busses/i2c-tegra.c | 35 +++++++++++++++++++++-------------
>>>  2 files changed, 38 insertions(+), 13 deletions(-)
>>>
>>
>> 2KB is a too small difference to justify the ifdefs and Kconfig entries,
>> IMO.
> 
> Maybe I should have mentioned that it's ~20%? With my "embedded" hat on:
> I think it might be small, but sometimes it is the difference between
> bootable kernel or one too big.

10KB is a small size too. I'm very doubtful that such changes make any
real difference in practice.

Much more practical should be to modularize more kernel code. You should
be able to squeeze zImage down to 3MB without any code changes by
toggling more kernel config options to =m. Try to use grate_defconfig
[1] for the base, that is what postmarketOS kernel build uses.

[1]
https://github.com/grate-driver/linux/blob/master/arch/arm/configs/grate_defconfig