linux-kernel - Re: [PATCH v3] serial: 8250: add gpio support to exar

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Date:	Mon, 21 Dec 2015 20:28:51 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v3] serial: 8250: add gpio support to exar

On Mon, Dec 21, 2015 at 5:19 PM, Sudip Mukherjee
<sudipm.mukherjee@...il.com> wrote:

> diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
> index 6412f14..ec3d287 100644
> --- a/drivers/tty/serial/8250/Kconfig
> +++ b/drivers/tty/serial/8250/Kconfig
> @@ -378,3 +378,11 @@ config SERIAL_8250_MID
>           Selecting this option will enable handling of the extra features
>           present on the UART found on Intel Medfield SOC and various other
>           Intel platforms.
> +
> +config SERIAL_8250_EXAR_GPIO
> +       bool "Support for GPIO pins on XR17V352/354/358"
> +       depends on SERIAL_8250_PCI && GPIOLIB
> +       select GPIO_SYSFS
> +       help
> +         Selecting this option will enable handling of GPIO pins present
> +         on Exar XR17V352/354/358 chips.
> diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
> index e177f86..1d0fce0 100644
> --- a/drivers/tty/serial/8250/Makefile
> +++ b/drivers/tty/serial/8250/Makefile
> @@ -28,5 +28,8 @@ obj-$(CONFIG_SERIAL_8250_MT6577)      += 8250_mtk.o
>  obj-$(CONFIG_SERIAL_8250_UNIPHIER)     += 8250_uniphier.o
>  obj-$(CONFIG_SERIAL_8250_INGENIC)      += 8250_ingenic.o
>  obj-$(CONFIG_SERIAL_8250_MID)          += 8250_mid.o
> +obj-$(CONFIG_SERIAL_8250_EXAR_GPIO)    += exar_gpio.o
> +exar_gpio-y                            := 8250_pci.o 8250_gpio.o
> +
>
>  CFLAGS_8250_ingenic.o += -I$(srctree)/scripts/dtc/libfdt
>
>
> But I am getting:
> ERROR: "xr17v35x_gpio_exit" [drivers/tty/serial/8250/8250_pci.ko] undefined!
> ERROR: "xr17v35x_gpio_init" [drivers/tty/serial/8250/8250_pci.ko] undefined!
>
> I will need little hint for the Makefile, please. Its clear that i have
> messed up.

Yes, read my previous mail.

There are at least two approaches:
 - use 8250_pci, etc as a library (see example: 8250_mid.c)
 - force 8250_pci to use external libraries in some cases (seems your approach)

In the latter you have to extend 8250_pci and rename it. I have no
idea if Greg or anyone else gives a green light for that.

Something like this (forget syntax of ifs in Makefile though
obj-(…8250_PCI) += 8250_pci.o
obj-8250_pci = 8250_pci_orig.o
ifneq (…EXAR_GPIO,)
obj-8250_pci += exar_gpio.o
endif

But what I can recommend is to split exar parts out of 8250_pci first
to a separate driver, do your part as a part of that new driver.
Of course better to gather maintainer's opinion first.

-- 
With Best Regards,
Andy Shevchenko
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