linux-kernel - Re: [PATCH v7 0/4] Extend device_get_match_data() to struct bus

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Date:   Mon, 14 Aug 2023 15:12:24 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jonathan Cameron <jic23@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peter Rosin <peda@...ntia.se>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        Andi Shyti <andi.shyti@...nel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v7 0/4] Extend device_get_match_data() to struct bus_type

Hi Biju,

On Fri, Aug 11, 2023 at 4:46 PM Biju Das <biju.das.jz@...renesas.com> wrote:
> > Subject: Re: [PATCH v7 0/4] Extend device_get_match_data() to struct
> > bus_type
> >
> > On Fri, Aug 11, 2023 at 01:27:36PM +0000, Biju Das wrote:
> > > > On Thu, Aug 10, 2023 at 09:05:10AM +0000, Biju Das wrote:
> >
> > ...
> >
> > > > I'm good with this approach, but make sure you checked the whole
> > > > kernel source tree for a such.
> > >
> > > Checking against 16 is too short I guess??
> > >
> > > drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h has 18 enums.
> >
> > So, what does prevent us from moving that tables to use pointers?
>
> I think that will lead to ABI breakage(client->name vs id->name)
>
>         match = device_get_match_data(&client->dev);
>         if (match) {
>                 chip_type = (uintptr_t)match;
>                 name = client->name;
>         } else if (id) {
>                 chip_type = (enum inv_devices)
>                         id->driver_data;
>                 name = id->name;
>         } else {
>                 return -ENOSYS;
>         }

I don't consider that part of the ABI, as e.g. converting from board files
to DT would change the name.
In addition, using id->name breaks multiple instances of the same device.

I applaud more unification ;-)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds