linux-kernel - Re: [PATCH 4/6] usb: chipidea: make configs for glue drivers visible with EXPERT

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Date:   Thu, 8 Sep 2022 13:33:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Lukas Bulwahn <lukas.bulwahn@...il.com>
Cc:     Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, Peter Chen <peter.chen@...nel.org>,
        linux-usb@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>, linux-mm@...ck.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        linux-kbuild@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] usb: chipidea: make configs for glue drivers visible
 with EXPERT

On Thu, Sep 08, 2022 at 12:43:35PM +0200, Lukas Bulwahn wrote:
> Commit 6a108a14fa35 ("kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT")
> introduces CONFIG_EXPERT to carry the previous intent of CONFIG_EMBEDDED
> and just gives that intent a much better name. That has been clearly a good
> and long overdue renaming, and it is clearly an improvement to the kernel
> build configuration that has shown to help managing the kernel build
> configuration in the last decade.
> 
> However, rather than bravely and radically just deleting CONFIG_EMBEDDED,
> this commit gives CONFIG_EMBEDDED a new intended semantics, but keeps it
> open for future contributors to implement that intended semantics:
> 
>     A new CONFIG_EMBEDDED option is added that automatically selects
>     CONFIG_EXPERT when enabled and can be used in the future to isolate
>     options that should only be considered for embedded systems (RISC
>     architectures, SLOB, etc).
> 
> Since then, this CONFIG_EMBEDDED implicitly had two purposes:
> 
>   - It can make even more options visible beyond what CONFIG_EXPERT makes
>     visible. In other words, it may introduce another level of enabling the
>     visibility of configuration options: always visible, visible with
>     CONFIG_EXPERT and visible with CONFIG_EMBEDDED.
> 
>   - Set certain default values of some configurations differently,
>     following the assumption that configuring a kernel build for an
>     embedded system generally starts with a different set of default values
>     compared to kernel builds for all other kind of systems.
> 
> Considering the first purpose, at the point in time where CONFIG_EMBEDDED
> was renamed to CONFIG_EXPERT, CONFIG_EXPERT already made 130 more options
> become visible throughout all different menus for the kernel configuration.
> Over the last decade, this has gradually increased, so that currently, with
> CONFIG_EXPERT, roughly 170 more options become visible throughout all
> different menus for the kernel configuration. In comparison, currently with
> CONFIG_EMBEDDED enabled, just seven more options are visible, one in x86,
> one in arm, and five for the ChipIdea Highspeed Dual Role Controller.
> 
> As the numbers suggest, these two levels of enabling the visibility of even
> more configuration options---beyond what CONFIG_EXPERT enables---never
> evolved to a good solution in the last decade. In other words, this
> additional level of visibility of configuration option with CONFIG_EMBEDDED
> compared to CONFIG_EXPERT has since its introduction never become really
> valuable. It requires quite some investigation to actually understand what
> is additionally visible and it does not differ significantly in complexity
> compared to just enabling CONFIG_EXPERT. This CONFIG_EMBEDDED---or any
> other config to show more detailed options beyond CONFIG_EXPERT---is
> unlikely to be valuable unless somebody puts significant effort in
> identifying how such visibility options can be properly split and creating
> clear criteria, when some config option is visible with CONFIG_EXPERT and
> when some config option is visible only with some further option enabled
> beyond CONFIG_EXPERT, such as CONFIG_EMBEDDED attempted to do. For now, it
> is much more reasonable to simply make those additional seven options that
> visible with CONFIG_EMBEDDED, visible with CONFIG_EXPERT, and then remove
> CONFIG_EMBEDDED. If anyone spends significant effort in structuring the
> visibility of config options, they may re-introduce suitable new config
> options simply as they see fit.
> 
> Make the configs for usb chipidea glue drivers visible when CONFIG_EXPERT
> is enabled.
> 
> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
> ---
>  drivers/usb/chipidea/Kconfig | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)

Now queued up in my USB tree, thanks.

greg k-h