Hi Linus,

On Thu, Mar 16, 2017 at 4:18 PM, Linus Walleij [off-list ref] wrote:

On Mon, Mar 6, 2017 at 11:02 AM, Uwe Kleine-K?nig
[off-list ref] wrote:

quoted

On Mon, Mar 06, 2017 at 10:53:27AM +0100, Geert Uytterhoeven wrote:

quoted

On Mon, Mar 6, 2017 at 10:30 AM, Uwe Kleine-K?nig

quoted

I wouldn't want to code this in each driver (something like:

        if (IS_ENABLED(GPIOLIB) || device_is_instantiated_by_dt(dev) || device_is_instantiated_by_acpi(dev))
                gpios = mctrl_gpio_init(...);
        else
                gpios = NULL;

). Putting this into GPIOLIB is the right approach, and so this is
another argument for HALFGPIOLIB. This would fix mctrl_gpio_init en
passant.

Do we have platforms where DT=y || ACPI=y, but GPIOLIB=n?
Ah, x86 ;-)

Yeah, and I think rm -r arch/x86 won't be acceptable :-) I assume you
can also configure some arm or powerpc systems without GPIOLIB.

quoted

Anyway, for sh-sci.c, platforms either have DT and GPIOLIB, or they do not
need mctrl-gpio.

So we're in agreement now that HALFGPIOLIB is the way to go?
Linus, what do you think?

OK modem lines over GPIO.

So the problem is that GPIOLIB is needed (obviously) for mctrl_gpio_init() to
work properly, and then there are some stubs in
drivers/tty/serial/serial_mctrl_gpio.h
for !GPIOLIB.

And this whole discussion is all about that !GPIOLIB case really,
whether DT, ACPI, SFI or board files machine data is used doesn't
really matter.

We're talking about:

quoted

git grep mctrl_gpio_init

drivers/tty/serial/atmel_serial.c:      atmel_port->gpios =
mctrl_gpio_init(&atmel_port->uart, 0);
drivers/tty/serial/clps711x.c:  s->gpios =
mctrl_gpio_init_noauto(&pdev->dev, 0);
drivers/tty/serial/etraxfs-uart.c:      up->gpios =
mctrl_gpio_init_noauto(&pdev->dev, 0);
drivers/tty/serial/imx.c:       sport->gpios = mctrl_gpio_init(&sport->port, 0);
drivers/tty/serial/mxs-auart.c: s->gpios = mctrl_gpio_init_noauto(dev, 0);
drivers/tty/serial/sh-sci.c:    sciport->gpios =
mctrl_gpio_init(&sciport->port, 0);

Atmel, ARM, ETRAX, ARM, ARM, Super-H, all have GPIOLIB.
Right now no x86, correct?

It's not that black-and-white. Some of SuperH have GPIOLIB, other parts don't.

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.

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