Hi Linus,

On Thu, Mar 16, 2017 at 5:38 PM, Geert Uytterhoeven
[off-list ref] wrote:

quoted

They actually all even do things like this in Kconfig:

config SERIAL_ATMEL
(...)
        select SERIAL_MCTRL_GPIO if GPIOLIB

What stops us from removing all the stubs in
drivers/tty/serial/serial_mctrl_gpio.h
and just make SERIAL_MCTRL_GPIO depends on GPIOLIB?

Removing the stubs implies adding #ifdefs to the drivers that need
to handle the !SERIAL_MCTRL_GPIO case.

E.g. I don't want to break the sh-sci serial driver on SuperH platforms that
(a) don't select GPIOLIB, and
(b) don't use mtrl_gpio.

Alternatively, after commit 22c403676dbbb7c6 ("gpio: return NULL from
gpiod_get_optional when GPIOLIB is disabled") we might just drop the
dependency of SERIAL_MCTRL_GPIO on GPIOLIB? Then no special handling
is needed in drivers, as all GPIOs will just be considered not present.

Documentation/gpio/consumer.txt rightfully sates:
| Note that gpio_get*_optional() functions (and their managed variants), unlike
| the rest of gpiolib API, also return NULL when gpiolib support is disabled.
| This is helpful to driver authors, since they do not need to special case
| -ENOSYS return codes.  System integrators should however be careful to enable
| gpiolib on systems that need it.

drivers/tty/serial/serial_mctrl_gpio.o already compiles fine if
CONFIG_GPIOLIB=n, which reduces its size by ca. 25%.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at 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