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Groups > linux.kernel > #1607444
| From | Geert Uytterhoeven <geert@linux-m68k.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls |
| Date | 2017-03-23 13:50 +0100 |
| Message-ID | <toalI-2iG-3@gated-at.bofh.it> (permalink) |
| References | (6 earlier) <to80y-ML-23@gated-at.bofh.it> <to8ae-TC-21@gated-at.bofh.it> <to8WB-1rG-9@gated-at.bofh.it> <to9J0-21Y-19@gated-at.bofh.it> <toac1-2e7-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Hi Uwe,
On Thu, Mar 23, 2017 at 1:34 PM, Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> On Thu, Mar 23, 2017 at 01:03:56PM +0100, Geert Uytterhoeven wrote:
>> On Thu, Mar 23, 2017 at 12:11 PM, Uwe Kleine-König
>> <u.kleine-koenig@pengutronix.de> wrote:
>> >> Make sure to enable all drivers and subsystems you need when building
>> >> your kernel. That's always true. And may indeed be hard to debug (e.g. what
>> >> kernel options do I need to make systemd work?).
>> >
>> > It's worse here. If you forget to enable a driver the device isn't bound
>> > and that's obvious to diagnose. When ignoring an optional GPIO there
>> > might be a device that claims to work but fails to do so. (e.g. you
>> > write to memory, write() returns 0, but the data never landed there.)
>> >
>> >> > write(2) and close(2) succeed most of the time, too. Still it's not a
>> >> > good idea to not check the return value. Or let the kernel return
>> >> > success unconditionally.
>> >>
>> >> Writing all bytes passed in the buffer is "optional" in another sense than
>> >> an "optional" GPIO: you must retry the write, while you can continue if
>> >> an optional GPIO is not present.
>> >
>> > And that is the point. You can continue *iff* the optional GPIO is not
>> > present. The patch in question removes the ability to determine if that
>> > GPIO is present and claims it is not present.
>>
>> If you forget to enable a driver/subsystem, you sometimes cannot determine
>> if the device is present or not neither.
>>
>> Hence it boils down to "knowing" if there is a GPIO or not.
>> So, when can there be a GPIO?
>> 1. The GPIO is described in DT.
>> => Not an issue, as DT GPIO implies GPIOLIB,
>> 2. The GPIO is described in legacy platform data.
>> => The platform code should make sure GPIOLIB is selected when needed.
>>
>> Issue solved?
>
> I like it better to not rely on platform code to do the right thing.
;-)
> Maybe we can make gpiod_get_optional look like this:
>
> if (!dev->of_node && isnt_a_acpi_device(dev) && !IS_ENABLED(GPIOLIB))
> return NULL;
> else
> return -ENOSYS;
>
> I don't know how isnt_a_acpi_device looks like, probably it involves
> CONFIG_ACPI and/or dev->acpi_node.
>
> This should be safe and still comfortable for legacy platforms, isn't it?
Yes, that should do the trick.
No feedback from me about ACPI.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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
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Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Linus Walleij <linus.walleij@linaro.org> - 2017-03-16 16:30 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-16 17:40 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-20 11:00 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-20 11:20 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-20 11:40 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-20 12:00 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-20 12:10 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Linus Walleij <linus.walleij@linaro.org> - 2017-03-23 10:40 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-23 11:20 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-23 11:30 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-23 12:20 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-23 13:10 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-23 13:40 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-23 13:50 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Linus Walleij <linus.walleij@linaro.org> - 2017-03-23 14:50 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-03-23 15:50 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-03-23 16:50 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-23 20:20 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-03-23 21:00 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-24 09:30 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-24 09:40 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-24 10:00 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-24 10:20 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-24 10:50 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-24 11:10 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Geert Uytterhoeven <geert@linux-m68k.org> - 2017-03-24 09:40 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Linus Walleij <linus.walleij@linaro.org> - 2017-03-24 10:00 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-03-23 17:00 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Linus Walleij <linus.walleij@linaro.org> - 2017-03-23 14:40 +0100
Re: [PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls Uwe Kleine-König <u.kleine-koenig@pengutronix.de> - 2017-03-16 17:40 +0100
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