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Groups > linux.kernel > #1608211
| 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 | 2017-03-24 09:40 +0100 |
| Message-ID | <tosVj-7gO-7@gated-at.bofh.it> (permalink) |
| References | (6 earlier) <tocdP-3va-9@gated-at.bofh.it> <tod9U-4dr-7@gated-at.bofh.it> <togr8-6L0-17@gated-at.bofh.it> <toh3Q-72e-29@gated-at.bofh.it> <tosLD-7cp-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Hi Uwe,
On Fri, Mar 24, 2017 at 9:00 AM, Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Subject: [PATCH] gpiod: let get_optional return NULL in some cases with GPIOLIB disabled
>
> People disagree if gpiod_get_optional should return NULL or
> ERR_PTR(-ENOSYS) if GPIOLIB is disabled. The argument for NULL is that
> the person who decided to disable GPIOLIB is assumed to know that there
> is no GPIO. The reason to stick to ERR_PTR(-ENOSYS) is that it might
> introduce hard to debug problems if that decision is wrong.
>
> So this patch introduces a compromise and let gpiod_get_optional (and
> its variants) return NULL if the device in question cannot have an
> associated GPIO because it is neither instantiated by a device tree nor
> by ACPI.
>
> This should handle most cases that are argued about.
>
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
> include/linux/gpio/consumer.h | 55 ++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 46 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
> index fb0fde686cb1..0ca29889290d 100644
> --- a/include/linux/gpio/consumer.h
> +++ b/include/linux/gpio/consumer.h
> @@ -161,20 +161,48 @@ gpiod_get_index(struct device *dev,
> return ERR_PTR(-ENOSYS);
> }
>
> -static inline struct gpio_desc *__must_check
> -gpiod_get_optional(struct device *dev, const char *con_id,
> - enum gpiod_flags flags)
> +static inline bool __gpiod_no_optional_possible(struct device *dev)
> {
> - return ERR_PTR(-ENOSYS);
> + /*
> + * gpiod_get_optional et al can only provide a GPIO if at least one of
> + * the backends for specifing a GPIO is available. These are device
> + * tree, ACPI and gpiolib's lookup tables. The latter isn't available if
> + * GPIOLIB is disabled (which is the case here).
> + * So if the provided device is unrelated to device tree and ACPI, we
> + * can be sure that there is no optional GPIO and let gpiod_get_optional
> + * safely return NULL.
> + * Otherwise there is still a chance that there is no GPIO but we cannot
> + * be sure without having to enable a part of GPIOLIB (i.e. the lookup
> + * part). So lets play safe and return an error. (Though there are also
> + * arguments that returning NULL then would be beneficial.)
> + */
> +
> + if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
> + return false;
At first sight, I though this was OK:
1. On ARM with DT, we can assume CONFIG_GPIOLOB=y.
2. I managed to configure an SH kernel with CONFIG_GPIOLOB=n, CONFIG_OF=y,
and CONFIG_SERIAL_SH_SCI=y, but since SH boards with SH-SCI UARTs do
not use DT (yet), the check for dev->of_node (false) should handle
that.
3. However, I managed to do the same for h8300, which does use DT. Hence
if mctrl_gpio would start relying on gpiod_get_optional(), this would
break the sh-sci driver on h8300 :-(
Note that h8300 doesn't have any GPIO drivers (yet?), so
CONFIG_GPIPOLIB=n makes perfect sense!
So I'm afraid the only option is to always return NULL, and put the
responsability on the shoulders of the system integrator...
> + if (IS_ENABLED(CONFIG_ACPI) && dev && ACPI_COMPANION(dev))
> + return false;
No comments about the ACPI case.
> static inline struct gpio_desc *__must_check
> gpiod_get_index_optional(struct device *dev, const char *con_id,
> unsigned int index, enum gpiod_flags flags)
> {
> + if (__gpiod_no_optional_possible(dev))
> + return NULL;
> +
> return ERR_PTR(-ENOSYS);
Regardless of the above, given you use the exact same construct in four
locations, what about letting __gpiod_no_optional_possible() return the NULL
or ERR_PTR itself, and renaming it to e.g. __gpiod_no_optional_return_value()?
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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