[U-Boot] [PATCH 1/2] common: mark commands as default to match "config_cmd_default.h"

[Masahiro YAMADA]

Hi

2015-01-15 23:46 GMT+09:00 Simon Glass <sjg at chromium.org>:
> Hi,
>
> On 14 January 2015 at 01:18, Alexey Brodkin <Alexey.Brodkin at synopsys.com> wrote:
>> Hi Simon, Masahiro-san,
>>
>> On Tue, 2015-01-13 at 20:18 -0800, Simon Glass wrote:
>>> >
>>> >> Probably I'm missing details of our Kconfig migration plan if one
>>> >> exists. Then I'd like to get a reference to the plan so I'm not
>>> >> attempting to do things that are already scheduled and could be even in
>>> >> a process of implementation.
>>> >> Otherwise if there's no current plan for Kconfig migration we may start
>>> >> discussion on how to deal with "commands" in particular.
>>> >
>>> >
>>> > I proposed the following way, but no big conversion movement has happened yet.
>>> > http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/199965/focus=200089
>>> >
>>> > If you have an idea, please propose it.
>>
>> Unfortunately I cannot open this link - I see "Connection to 80.91.229.5
>> failed". Do you mind to provide a link for the same message in
>> http://lists.denx.de ?
>>
>>
>>> > Kconfig conversion is a too big task to be done by a single indivisual.
>>> > Any suggestion, any form of contribution is very appreciated.
>>
>> Indeed and that stops me from starting this work as well.
>> So my point is:
>>  1) anybody may do updates to Kconfig like add more U-Boot commands,
>> some settings (CONFIG_SYS_xxx)
>>  2) board maintainers are responsible for updates in defconfigs and
>> corresponding headers in "include/configs/"
>>  3) that would be helpful if at (1) board maintainers are notified via
>> direct emails on the change that has been done
>>
>>> > I personally keep away from any global changes until
>>> > non-generic boards are dumped.
>>> >
>>> > As Tom said in the following mail,
>>> > http://lists.denx.de/pipermail/u-boot/2015-January/201032.html
>>> > we are going to remove lots of boards.
>>> >
>>> > I do not want to make extra efforts on non-generic boards.
>>
>> That makes sense but why don't we start implementation of changes in
>> good boards we know already converted to "generic"? There're even entire
>> arches that switched to "generic boards".
>>
>>> >> The point is commands are low-hanging fruits in terms of Kconfig
>>> >> migration - there're no extra options and tweaks, once all commands are
>>> >> added in Kconfig (essentially with dependencies etc) we may clean all
>>> >> board headers. The only real problem here is amount of work - lots of
>>> >> headers/defconfigs to patch. But still this is doable.
>>> >
>>> >
>>> > I realized one problem when I was doing this task
>>> > for my boards in commit 25e274e20208.
>>> >
>>> > The defconfigs of my boards are almost the same:
>>> > (configs/ph1_ld4_defconfig, configs/ph1_pro4_defconfig, configs/ph1_sld8_defconfig)
>>> >
>>> > What is inconvenient as for defconfig is that
>>> > it does not support "include" directive like C headers.
>>> >
>>> > People generally like to add CONFIG_CMD_* to a common header file
>>> > such as include/configs/tegra-common.h
>>> >
>>> > On the other hand, on defconfig, we must touch each defconfig of the board family.
>>> >
>>> > I have not been able to decide right direction to solve this issue.
>>> >
>>> > I think we need to discuss about how to live with lots of defconfigs.
>>>
>>> How about this:
>>>
>>> 1. Support an 'include' option in defconfig to include another file.
>>> This could take the form of CONFIG_DEFCONFIG_INCLUDES (comma-separated
>>> list of filenames). Don't allow nested includes - this CONFIG provides
>>> a complete list of includes.
>>> 2. When you use menuconfig to edit the config, it ignores the include
>>> and just writes out everything. Then it runs a simple script which
>>> parses the include files, and adjusts the file so that things in the
>>> includes are not repeated in the defconfig.
>>>
>>> I think this scheme would be good enough, but can probably be
>>> improved. At least it would be better than what we have.
>>>
>>> Or we could instead define particular includes for different purposes:
>>>
>>> - Arch
>>> - SOC
>>> - SOC Vendor
>>> - Board vendor
>>> - Board family
>>>
>>> We could then require that standard filenames are used, and search for
>>> the correct file based on the SOC/board/vendor setting, etc.
>>>
>>> As an example, for trimslice, we could search for arm.h, tegra.h,
>>> nvidia.h, compulab.h, some_family_name.h.
>>>
>>> This is less flexible though.
>>
>> Frankly I don't like this approach with post-processing steps. It will
>> inevitably end-up with messed up configs.
>>
>> Why don't we just use default values in Kconfig for ARCH/SOC/Board?
>> It's pretty obvious that 1 board may have N flavors but then have a
>> baseline options selected in "board/vendor/board_name/Kconfig" and only
>> put options that differ between boards in your defconfigs.
>>
>> This way "savedefconfig" will automatically strip down all extra lines
>> for a particular board.
>>
>> This is how things work in Linux kernel and Buildroot Kconfig-based
>> build systems. Probably I'm missing something here because U-Boot
>> differs from mentioned projects in some aspects - if so please correct
>> me.
>
> I started with this approach and Masahiro was not very keen on it. I'm
> OK with it, particularly as it is already supported, but I wonder
> whether we can do better.

Honestly, I do not like baseline options in board-Kconfig very much.
The advantage is that it works without any change.


What I suggested before was to use scripts/kconfig/merge_config.sh.

For example, put the SoC baseline options into tegra30_defconfig.
Put the difference from that into tegra30_(board).config
For example,

    make  tegra30_defconfig  tegra30_seaboard.config
    make  tegra30_defconfig  tegra30_trimslice.config

The disadvantage is that we would have to input more for the configuration
and has some impact on other projects such as BuildRoot...



Another option is "multi-image".
Actually barebox adopted this solution to solve the increasing
defconfig problem.

In barebox, for example, all the Tegra boards share a single
defconfig, "tegra_v7_defconfig"

tegra_v7_defconfig  creates images for beaver, jetson, colibri, ac100, ...

It takes advantage of Device Tree configuration and garbage collection.
So, it generates multipule images without increasing memory foot-print.




> I notice that some kernel distributions have a script which pulls out
> common kernel configs in a separate file (e.g. for ARM, or for Tegra)
> for checking into source control, then combine them again for the
> kernel. This suggests that others have this problem too. It does seem
> like a convenient feature to be able to have some sort of hierarchy of
> config.
>
> Re messed-up configs, what will mess up? We can make it part of
> writing the config, perhaps.

The hierarchical config strategy makes "savedefconfig" difficult , I think.



>>
>>> >>
>>> >> That's a separate topic. I do agree that CMD_FPGA makes not much sense
>>> >> for most of boards, as well as some others.
>>> >>
>>> >> And I think during migration process of commands to Kconfig it's a good
>>> >> time to reconsider default commands.
>>> >
>>> > Agree.
>>> > We should reconsider the default.
>>> > In my opition, most of the ones in config_cmd_default.h are not default commands.
>>
>> Right but if we expect to switch to Kconfig solely for commands
>> selection we may not care much about contents of "config_cmd_default.h"
>> assuming it will go away sometime soon.
>>
>> Probably we may just focus on:
>> 1. Add all existing commands in Kconfig
>> 2. Select very few of them to be globally default
>>
>> (1) is pretty simple and anybody may do it if time permits
>> (2) requires wide discussion
>>
>> But what's really nice with Kconfig is its "savedefconfig". So we may
>> not set any commands as globally default and let every architecture,
>> board or defconfig to select really required options.
>>
>> Then once any option is marked as global (or even arch or board) default
>> in a matter of simple script that does "make XXX_defconfig && make
>> savedefconfig && mv defconfig configs/XXX_defconfig" all relevant
>> defconfigs will be correctly updated (default options will be stripped
>> out).
>
> Yes, it would be great to get all command configs into Kconfig.
>
> I wonder if we need a script which automates the conversion? The
> header file includes in the include/configs/... files makes this
> non-trivial. But if we had a script which could take a CONFIG as a
> parameter, remove it from all config headers, and add it to relevant
> defconfigs, it would be very useful.

I have a Python script that moves each CONFIG from header files to
defconfig files.

I wrote it for my local use, so it might not be very clean.


If necessary, I can share it on ML.




-- 
Best Regards
Masahiro Yamada