Date:   Sat, 2 Jan 2021 08:12:30 +0800
From:   Hongyi Zhao <hongyi.zhao@...il.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: Generate the config file for kernel compilation non-interactively
 in script.

On Sat, Jan 2, 2021 at 12:28 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> Hi,
>
> On 1/1/21 1:55 AM, Hongyi Zhao wrote:
> > On Fri, Jan 1, 2021 at 2:32 PM Randy Dunlap <rdunlap@...radead.org> wrote:
> >>
> >> On 12/31/20 8:51 PM, Hongyi Zhao wrote:
> >>> Hi,
> >>>
> >>> I want to build the realtime Linux for ROS 2 according to the
> >>> guidelines here:
> >>> <https://index.ros.org/doc/ros2/Tutorials/Building-Realtime-rt_preempt-kernel-for-ROS-2/>.
> >>>
> >>> For this purpose, I must enable the rt_preempt relative options in the
> >>> kernel withe the following method interactively:
> >>>
> >>> $ make menuconfig
> >>>
> >>> and set the following
> >>>
> >>> # Enable CONFIG_PREEMPT_RT
> >>>  -> General Setup
> >>>   -> Preemption Model (Fully Preemptible Kernel (Real-Time))
> >>>    (X) Fully Preemptible Kernel (Real-Time)
> >>>
> >>> # Enable CONFIG_HIGH_RES_TIMERS
> >>>  -> General setup
> >>>   -> Timers subsystem
> >>>    [*] High Resolution Timer Support
> >>>
> >>> # Enable CONFIG_NO_HZ_FULL
> >>>  -> General setup
> >>>   -> Timers subsystem
> >>>    -> Timer tick handling (Full dynticks system (tickless))
> >>>     (X) Full dynticks system (tickless)
> >>>
> >>> # Set CONFIG_HZ_1000 (note: this is no longer in the General Setup
> >>> menu, go back twice)
> >>>  -> Processor type and features
> >>>   -> Timer frequency (1000 HZ)
> >>>    (X) 1000 HZ
> >>>
> >>> # Set CPU_FREQ_DEFAULT_GOV_PERFORMANCE [=y]
> >>>  ->  Power management and ACPI options
> >>>   -> CPU Frequency scaling
> >>>    -> CPU Frequency scaling (CPU_FREQ [=y])
> >>>     -> Default CPUFreq governor (<choice> [=y])
> >>>      (X) performance
> >>>
> >>> But this is very inconvenient for doing the above job in script. Is
> >>> there an alternative method to generate the above configurations for
> >>> kernel compilation  non-interactively in script.
> >>
> >> Hi,
> >> You can use scripts/config in the kernel source tree.
> >> Something like this (I don't have RT kernel sources):
> >>
> >>
> >> scripts/config -e PREEMPT_RT
> >> scripts/config -e HIGH_RES_TIMERS
> >> scripts/config -e NO_HZ_FULL
> >> scripts/config -e HZ_1000
> >> scripts/config -e CPU_FREQ_DEFAULT_GOV_PERFORMANCE
> >
> > Wonderful. Thanks a lot for your instructions. I really have noticed
> > this tool but failed to figure out the corresponding translation rules
> > for the options used by menuconfig and this script.
> >
> > BTW, how do you figure out the above options/arguments corresponding
> > to the ones I've mentioned previously?
> >
>
> Oh, I just took the ones that you had listed and removed the leading
> "CONFIG_" from them.
>
> >>
> >> Note that if any of those have other Kconfig dependencies, those Kconfig
> >> symbols will also have to be enabled for this to work.
> >
> > How to know whether an option has other Kconfig dependencies and find
> > the corresponding symbols/arguments for feeding to scripts/config?
>
> Use one of the interactive config tools (nconfig, xconfig).
> They will show you dependencies, but you may have to enable other
> symbols first.
>
> Maybe it would be easier to do a temporary 'make allmodconfig'
> to have the symbols that you are interested in be enabled, then
> you can find them and look at their dependencies.

It sounds still complicated for manually operation of the above
mentioned procedure even by the virtue of scripts/config. The more
feasible way should be done with python package/binding/library
programmatically, but I'm not sure whether such stuff exists.

BR,
-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@...il.com>
Theory and Simulation of Materials
Hebei Polytechnic University of Science and Technology engineering
NO. 552 North Gangtie Road, Xingtai, China

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