From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Dirk Gouders <dirk@gouders.net>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Michal Marek <michal.lkml@markovi.net>,
Sam Ravnborg <sam@ravnborg.org>,
Ulf Magnusson <ulfalizer@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] kconfig: report recursive dependency involving 'imply'
Date: Wed, 15 Aug 2018 15:27:13 +0900 [thread overview]
Message-ID: <CAK7LNAQBu47aB56wpK29Aixnw9vEDVc2V8zwstVBrusBwuz6Gg@mail.gmail.com> (raw)
In-Reply-To: <gh8t59utb2.fsf@lena.gouders.net>
2018-08-14 19:38 GMT+09:00 Dirk Gouders <dirk@gouders.net>:
> Masahiro Yamada <yamada.masahiro@socionext.com> writes:
>
>> Currently, Kconfig does not report anything about the recursive
>> dependency where 'imply' keywords are involved.
>>
>> [Test Code]
>>
>> config A
>> bool "a"
>>
>> config B
>> bool "b"
>> imply A
>> depends on A
>
> Hello Masahiro,
>
> obviously, it is hard to find a reason why one wants to use dependencies
> like above but I also wonder how e.g. menuconfig handles this case:
>
> First, only "a" is visible, if I then select "a", "b" does not become
> visible but when I then reset "a" to "n", "b" becomes visible. If I then
> try to select "b", it becomes invisible...
>
> Perhaps it would be better to just error out instead of giving users the
> impression, Kconfig thinks such questionable behavior is OK.
Taking closer look at the code, the intention is 'recursive dependency
is error',
but the behavior changed probably by an accident.
I fixed this:
https://patchwork.kernel.org/patch/10566301/
> Side note: perhaps, the documentation could be better when it comes to
> recursive dependencies. The documentation says "select" and
> "imply" can be used to specify lower limits whereas direct
> dependencies specify upper limits for symbol values and with
> this in mind, one might wonder why it is a problem to work
> with both limits in a recursive way.
>
> Not very unlikely that it is just me who still has to
> understand recursive dependencies or problems with reading
> English text, though.
To avoid confusion, two things should be discussed separately:
[1] Unmet dependency
This is caused by a conflict between the upper limit from 'depends on'
and the lower limit from 'select'.
This issue does not happen for 'imply' because the upper limit
specified by 'imply' is weaker.
[2] Recursive depenency
This can happen for any combination of 'depends on',
'select', 'imply', 'if', 'default', etc.
> What definitely seems to get void with your patches is item c) in
> "Practical solutions to kconfig recursive issue" in
> Documentation/kbuild/kconfig-language:
>
> c) Consider the use of "imply" instead of "select"
I do not know why commit 237e3ad0f195d8 added this line.
Actually, I was also confused.
I sent v2 based on your feedback.
Thanks.
> Dirk
>
>> In the code above, Kconfig cannot calculate the symbol values correctly
>> due to the circular dependency. For example, allyesconfig followed by
>> syncconfig results in an odd behavior because CONFIG_B becomes visible
>> in syncconfig.
>>
>> $ make allyesconfig
>> scripts/kconfig/conf --allyesconfig Kconfig
>> #
>> # configuration written to .config
>> #
>> $ cat .config
>> #
>> # Automatically generated file; DO NOT EDIT.
>> # Main menu
>> #
>> CONFIG_A=y
>> $ make syncconfig
>> scripts/kconfig/conf --syncconfig Kconfig
>> *
>> * Restart config...
>> *
>> *
>> * Main menu
>> *
>> a (A) [Y/n/?] y
>> b (B) [N/y/?] (NEW)
>>
>> To report this correctly, sym_check_expr_deps() should recurse to
>> not only sym->rev_dep.expr but also sym->implied.expr .
>>
>> At this moment, sym_check_print_recursive() cannot distinguish
>> 'select' and 'imply' since it does not know the precise context
>> where the recursive dependency is hit. This will be solved by
>> the next commit.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>> ---
>>
>> scripts/kconfig/symbol.c | 9 +++++++--
>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
>> index 4ec8b1f..7de7463a 100644
>> --- a/scripts/kconfig/symbol.c
>> +++ b/scripts/kconfig/symbol.c
>> @@ -1098,7 +1098,7 @@ static void sym_check_print_recursive(struct symbol *last_sym)
>> sym->name ? sym->name : "<choice>",
>> next_sym->name ? next_sym->name : "<choice>");
>> } else {
>> - fprintf(stderr, "%s:%d:\tsymbol %s is selected by %s\n",
>> + fprintf(stderr, "%s:%d:\tsymbol %s is selected or implied by %s\n",
>> prop->file->name, prop->lineno,
>> sym->name ? sym->name : "<choice>",
>> next_sym->name ? next_sym->name : "<choice>");
>> @@ -1161,8 +1161,13 @@ static struct symbol *sym_check_sym_deps(struct symbol *sym)
>> if (sym2)
>> goto out;
>>
>> + sym2 = sym_check_expr_deps(sym->implied.expr);
>> + if (sym2)
>> + goto out;
>> +
>> for (prop = sym->prop; prop; prop = prop->next) {
>> - if (prop->type == P_CHOICE || prop->type == P_SELECT)
>> + if (prop->type == P_CHOICE || prop->type == P_SELECT ||
>> + prop->type == P_IMPLY)
>> continue;
>> stack.prop = prop;
>> sym2 = sym_check_expr_deps(prop->visible.expr);
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2018-08-15 6:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-14 6:43 [PATCH 1/2] kconfig: report recursive dependency involving 'imply' Masahiro Yamada
2018-08-14 6:43 ` [PATCH 2/2] kconfig: improve the recursive dependency report Masahiro Yamada
2018-08-14 10:38 ` [PATCH 1/2] kconfig: report recursive dependency involving 'imply' Dirk Gouders
2018-08-14 13:44 ` Dirk Gouders
2018-08-15 6:29 ` Masahiro Yamada
2018-08-15 6:27 ` Masahiro Yamada [this message]
2018-08-15 13:10 ` Dirk Gouders
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAK7LNAQBu47aB56wpK29Aixnw9vEDVc2V8zwstVBrusBwuz6Gg@mail.gmail.com \
--to=yamada.masahiro@socionext.com \
--cc=dirk@gouders.net \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=michal.lkml@markovi.net \
--cc=sam@ravnborg.org \
--cc=ulfalizer@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).