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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Tue, 13 Feb 2018 19:01:37 +0200
Message-ID: <CAHp75Vc9T8umLVtBuBCK+HgAga9=ZKBhBTjA8Nmbvaw1zyVLng@mail.gmail.com>
Subject: Re: [PATCH v2] i2c: i801: Register optional lis3lv02d i2c device on
 Dell machines
To:     =?UTF-8?Q?Pali_Roh=C3=A1r?= <pali.rohar@gmail.com>
Cc:     Jean Delvare <jdelvare@suse.com>, Wolfram Sang <wsa@the-dreams.de>,
        =?UTF-8?B?TWljaGHFgiBLxJlwaWXFhA==?= <kernel@kempniu.pl>,
        Steven Honeyman <stevenhoneyman@gmail.com>,
        Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
        Jochen Eisinger <jochen@penguin-breeder.org>,
        Gabriele Mazzotta <gabriele.mzt@gmail.com>,
        Andy Lutomirski <luto@kernel.org>,
        Mario Limonciello <Mario_Limonciello@dell.com>,
        Alex Hung <alex.hung@canonical.com>,
        Takashi Iwai <tiwai@suse.de>,
        linux-i2c <linux-i2c@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Platform Driver <platform-driver-x86@vger.kernel.org>
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On Tue, Feb 13, 2018 at 6:50 PM, Pali Roh=C3=A1r <pali.rohar@gmail.com> wro=
te:
> On Tuesday 13 February 2018 17:06:19 Andy Shevchenko wrote:
>> On Tue, Feb 13, 2018 at 5:00 PM, Pali Roh=C3=A1r <pali.rohar@gmail.com> =
wrote:
>> > On Tuesday 13 February 2018 16:55:00 Andy Shevchenko wrote:
>> >> On Mon, Feb 12, 2018 at 5:30 PM, Pali Roh=C3=A1r <pali.rohar@gmail.co=
m> wrote:
>> >> > On Wednesday 31 January 2018 14:27:51 Andy Shevchenko wrote:

>> >> > Following table already exists in dell-smo8800.c file:
>> >> > 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 an=
d
>> >> 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.
>
> I'm not maintainer of i2c-i801.ko, Jean Delvare & Wolfram Sang are.
> Therefore instructing future contributors would be up to them.

Right. But from ACPI prospective the proposed change is not okay by my opin=
ion.

How can I see what drivers are binding / relying on certain ACPI ID?

More precisely,

% git grep -n -w SMO8800

would be useless until one gets an idea to match against partial strings.

> Jean, it is OK?

>> > 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=
.
>
> But this is exactly what is needed. This ACPI ID table contains ACPI
> names which says if accelerometer is present or not.

In case of dell-smo8800.c the driver actually *binds* to these IDs.
Your change just provide another table to match and answer to the
question if XYZ is present on a such platform or not.

Similar approach is used in spi-pxa2xx.c (check pxa2xx_spi_pci_compound_mat=
ch).

--=20
With Best Regards,
Andy Shevchenko