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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 30 Jul 2019 10:00:36 +0200
Message-ID: <CAK8P3a16dON3g-BzUOrdHu3ryCD+FyJn29EwcT_aQAdj-jvFnA@mail.gmail.com>
Subject: Re: Marking legacy watchdog drivers as deprecated / obsolete
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     linux-watchdog@cger.kernel.org,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, Jul 30, 2019 at 12:07 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> Hi,
>
> we have recently seen a number of changes to legacy watchdog drivers,
> mostly surrounding the coding style used some 10+ years ago, but also
> fixing minor formatting or coding problems found by static analyzers.
> This slowly rises above the level of background noise.
>
> Would it be acceptable to mark all those drivers as deprecated/obsolete,
> warn users that the driver should be converted to use the watchdog
> subsystem, and that it will otherwise be removed in a later Linux kernel
> version ? This would give us an idea which drivers are still in use,
> and it would enable us to remove the remaining drivers maybe 5 or 6
> releases for now.
>
> Thoughts ?

I don't think an automated approach across 61 drivers is likely to work
well. About half of the drivers appear to be for specific SoCs, and
removing the watchdog driver while keeping the rest of the SoC support
would not be helpful, it  just means we break one of the drivers for the
last remaining users of an old SoC the next time they try to upgrade to
a new kernel.

It would probably be helpful to go through the list and see if any of
the drivers
are for platforms that are already gone. FWIW, here is the list of drivers that
have their own .ioctl() method, taken from a patch I'm sending soon
to add a .compat_ioctl handler:

arch/powerpc/platforms/52xx/mpc52xx_gpt.c
arch/um/drivers/harddog_kern.c
drivers/char/ipmi/ipmi_watchdog.c
drivers/hwmon/fschmd.c
drivers/rtc/rtc-ds1374.c
drivers/watchdog/acquirewdt.c
drivers/watchdog/advantechwdt.c
drivers/watchdog/alim1535_wdt.c
drivers/watchdog/alim7101_wdt.c
drivers/watchdog/ar7_wdt.c
drivers/watchdog/at91rm9200_wdt.c
drivers/watchdog/ath79_wdt.c
drivers/watchdog/bcm63xx_wdt.c
drivers/watchdog/cpu5wdt.c
drivers/watchdog/eurotechwdt.c
drivers/watchdog/f71808e_wdt.c
drivers/watchdog/gef_wdt.c
drivers/watchdog/geodewdt.c
drivers/watchdog/ib700wdt.c
drivers/watchdog/ibmasr.c
drivers/watchdog/indydog.c
drivers/watchdog/intel_scu_watchdog.c
drivers/watchdog/iop_wdt.c
drivers/watchdog/it8712f_wdt.c
drivers/watchdog/ixp4xx_wdt.c
drivers/watchdog/ks8695_wdt.c
drivers/watchdog/m54xx_wdt.c
drivers/watchdog/machzwd.c
drivers/watchdog/mixcomwd.c
drivers/watchdog/mtx-1_wdt.c
drivers/watchdog/mv64x60_wdt.c
drivers/watchdog/nuc900_wdt.c
drivers/watchdog/nv_tco.c
drivers/watchdog/pc87413_wdt.c
drivers/watchdog/pcwd.c
drivers/watchdog/pcwd_pci.c
drivers/watchdog/pcwd_usb.c
drivers/watchdog/pika_wdt.c
drivers/watchdog/pnx833x_wdt.c
drivers/watchdog/rc32434_wdt.c
drivers/watchdog/rdc321x_wdt.c
drivers/watchdog/riowd.c
drivers/watchdog/sa1100_wdt.c
drivers/watchdog/sb_wdog.c
drivers/watchdog/sbc60xxwdt.c
drivers/watchdog/sbc7240_wdt.c
drivers/watchdog/sbc_epx_c3.c
drivers/watchdog/sbc_fitpc2_wdt.c
drivers/watchdog/sc1200wdt.c
drivers/watchdog/sc520_wdt.c
drivers/watchdog/sch311x_wdt.c
drivers/watchdog/scx200_wdt.c
drivers/watchdog/smsc37b787_wdt.c
drivers/watchdog/w83877f_wdt.c
drivers/watchdog/w83977f_wdt.c
drivers/watchdog/wafer5823wdt.c
drivers/watchdog/wdrtas.c
drivers/watchdog/wdt.c
drivers/watchdog/wdt285.c
drivers/watchdog/wdt977.c
drivers/watchdog/wdt_pci.c

      Arnd