linux-kernel - Re: [PATCH v2] i2c: i801: Register optional lis3lv02d i2c device on Dell machines

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Date:   Tue, 13 Feb 2018 17:06:19 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Jean Delvare <jdelvare@...e.com>, Wolfram Sang <wsa@...-dreams.de>,
        Michał Kępień <kernel@...pniu.pl>,
        Steven Honeyman <stevenhoneyman@...il.com>,
        Valdis Kletnieks <Valdis.Kletnieks@...edu>,
        Jochen Eisinger <jochen@...guin-breeder.org>,
        Gabriele Mazzotta <gabriele.mzt@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Mario Limonciello <Mario_Limonciello@...l.com>,
        Alex Hung <alex.hung@...onical.com>,
        Takashi Iwai <tiwai@...e.de>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH v2] i2c: i801: Register optional lis3lv02d i2c device on
 Dell machines

On Tue, Feb 13, 2018 at 5:00 PM, Pali Rohár <pali.rohar@...il.com> wrote:
> On Tuesday 13 February 2018 16:55:00 Andy Shevchenko wrote:
>> On Mon, Feb 12, 2018 at 5:30 PM, Pali Rohár <pali.rohar@...il.com> wrote:
>> > On Wednesday 31 January 2018 14:27:51 Andy Shevchenko wrote:
>> >> On Wed, Jan 31, 2018 at 2:03 PM, Pali Rohár <pali.rohar@...il.com> wrote:
>> >> > On Sunday 28 January 2018 17:00:35 Andy Shevchenko wrote:
>> >> >> On Sun, Jan 28, 2018 at 4:45 PM, Pali Rohár <pali.rohar@...il.com> wrote:
>> >>
>> >> >> > ACPI device name is SMO8800, SMO8810, ... Will that acpi_dev_present
>> >> >> > function match only prefix and not exact string?
>> >> >>
>> >> >> OK, fair enough.
>> >> >>
>> >> >> Do we have more users of such pattern?
>> >> >
>> >> > I have not seen this ACPI pattern yet, so probably not.
>> >>
>> >> I see. So, my  one concern is the implicit names of the devices. I
>> >> would like rather to see
>> >>
>> >> ... acpi_device_id ... []= {
>> >>  {"SMO8800"},
>> >>  {"SMO8810"},
>> >> ...
>> >> {}
>> >> };
>> >
>> > Following table already exists in dell-smo8800.c file:
>> >
>> > static const struct acpi_device_id smo8800_ids[] = {
>> >         { "SMO8800", 0 },
>> >         { "SMO8801", 0 },
>> >         { "SMO8810", 0 },
>> >         { "SMO8811", 0 },
>> >         { "SMO8820", 0 },
>> >         { "SMO8821", 0 },
>> >         { "SMO8830", 0 },
>> >         { "SMO8831", 0 },
>> >         { "", 0 },
>> > };
>> >
>> > MODULE_DEVICE_TABLE(acpi, smo8800_ids);
>> >
>> > Can we reuse it?
>>
>> >  Maybe moving array smo8800_ids[] into some header file
>> > (which one?) and statically inline it?
>>
>> Bad idea.
>>
>> > Or having it only in
>> > dell-smo8800.c file and exporting its symbol?
>>
>> Even worse.
>>
>> > Or is there better idea?
>> >
>> > For sure I do not want to copy paste this table into another module and
>> > maintaining two copies of this list.
>>
>> The copy is fine. Can you guarantee that those two lists would be
>> always the same? I'm not.
>
> Me neither.
>
>> And besides that explicitly over implicitly  is a really good thing. I
>> would not like to grep for an ID followed by grepping include line and
>> check each files to check if it uses it or not.
>
> So what do you suggest now?

Copy'n'paste and maintain two lists.
Yes, it's not the ideal, but working solution.

You may put a comment before each list to explain what the second does
and tell a contributor to look at it and update if needed.

> Having one file where it would be defined is a bad idea for you.

Not just "one file", but "one *header* file". Or "exporting a symbol"
which is basically not supposed to be exported.
ID tables are part of the actual drivers, neither headers, nor libraries.

> And maintaining copy of same array in two different files in two
> different subsystems is something which I cannot guarantee.
>
> Therefore the current patch is the best approach.

I don't like it. I'll not take it, sorry.

> No shared file with
> shared array/table and also no copy of that array in two different
> subsystems.


-- 
With Best Regards,
Andy Shevchenko