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

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Date:   Tue, 13 Feb 2018 16:00:04 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...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 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?

Having one file where it would be defined is a bad idea for you.
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. No shared file with
shared array/table and also no copy of that array in two different
subsystems.

-- 
Pali Rohár
pali.rohar@...il.com