linux-kernel - Re: [RFC PATCH 0/5] Add CONFIG symbol as module attribute

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Date:   Mon, 22 Aug 2016 21:48:33 +0200
From:   Cristina-Gabriela Moraru <cristina.moraru09@...il.com>
To:     Michal Marek <mmarek@...e.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        "vegard.nossum@...il.com" <vegard.nossum@...il.com>,
        Valentin Rothberg <valentinrothberg@...il.com>,
        Hannes Reinecke <hare@...e.de>,
        Sam Ravnborg <sam@...nborg.org>, linux-kernel@...r.kernel.org,
        Tom Gundersen <teg@...m.no>, Kay Sievers <kay@...y.org>,
        Rusty Russell <rusty@...tcorp.com.au>,
        akpm@...ux-foundation.org, backports@...r.kernel.org,
        Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "rafael.j.wysocki" <rafael.j.wysocki@...el.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Takashi Iwai <tiwai@...e.de>, Christoph Hellwig <hch@....de>,
        Mauro Carvalho Chehab <mchehab@....samsung.com>,
        Johannes Berg <johannes@...solutions.net>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Paul Bolle <pebolle@...cali.nl>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Sathya Prakash Veerichetty <sathya.prakash@...adcom.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Laurence Oberman <loberman@...hat.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Tejun Heo <tj@...nel.org>,
        Jej B <James.Bottomley@...senpartnership.com>,
        "Theodore Ts'o" <tytso@....edu>, danijons@...dent.chalmers.se,
        Andrzej Wasowski <wasowski@....dk>
Subject: Re: [RFC PATCH 0/5] Add CONFIG symbol as module attribute

2016-08-19 11:07 GMT+02:00 Michal Marek <mmarek@...e.com>:
> On 2016-08-18 19:55, Luis R. Rodriguez wrote:
>> On Wed, Aug 17, 2016 at 09:26:58PM +0200, Cristina Moraru wrote:
>>
>>> This patchset implements dynamic pegging of kconfig symbol
>>> into driver modinfo section
>>
>> First a little bit of motivation here helps, so let me try to
>> help fill in some gaps. This may help explain what you have
>> been working on a bit more.
>>
>> First, for those that were not Cc'd but curious about this work
>> so far, you can read the patches here:
>>
>> Original cover letter:
>>
>> https://lkml.kernel.org/r/1471462023-119645-1-git-send-email-cristina.moraru09@gmail.com
>>
>> https://marc.info/?l=linux-kernel&m=147146213519750&w=2 - patch 1
>> https://marc.info/?l=linux-kernel&m=147146209019744&w=2 - patch 2
>> https://marc.info/?l=linux-kernel&m=147146211819747&w=2 - patch 3
>> https://marc.info/?l=linux-kernel&m=147146209119745&w=2 - patch 4
>> https://marc.info/?l=linux-kernel&m=147146209519746&w=2 - patch 5
>>
>> There are a few situations in which you may want to extract a
>> subset of Kconfig CONFIG_* symbols for a system. At least when
>> only considering modules:
>>
>>  a) When optimizing build requirements for a kernel for a system.
>>     That is you boot into a distro kernel and then want to build
>>     a slim kernel only with sensible kernel configuration options.
>>
>>  b) When you are on a distribution kernel but the distribution
>>     kernel provided lacks hardware support for your device, you
>>     may either want to upgrade the full kernel in which case you
>>     want to do a) or -- you may want to just a backports release
>>     which provides just the modules you need, you'd use it on top
>>     of the distribution kernel.
>
> c) Having the mapping in sysfs would allow to simplify
> streamline_config.pl avoid parsing Makefiles in perl. Only if the patch
> did not depend on streamline_config.pl :). One idea would be to generate
> the Module.ksymb in a similar way we generate the modules.builtin file:
> Generate an alternate include/config/*.conf with all CONFIG_FOO=m
> replaced with
>
> CONFIG_FOO=m-CONFIG_FOO
>
> and in the Makefile, iterate over $(filter m-CONFIG_%, $(.VARIABLES)) to
> create the mapping. This would also properly cover cases where we build
> the $(obj-m) list from another list. It would certainly create other
> corner cases, but it's worth trying IMO.
>

That's interesting.

> Another thing is that we do not necessarily need to record this
> information in .modinfo, but we can generate a list in
> /lib/modules/`uname -r`/ for consumption. It could also include drivers
> that are builtin in the current configuration.
>
> Michal

Thank you,

Cristina