gpio: add GPIO support for F71882FG and F71889F

This patch adds support for the GPIOs found on the Fintek super-I/O
chips F71882FG and F71889F.

A super-I/O is a legacy I/O controller embedded on x86 motherboards. It
is used to connect the low-bandwidth devices. Among others functions the
F71882FG/F71889F provides: a parallel port, two serial ports, a keyboard
controller, an hardware monitoring controller and some GPIO pins.

Note that this super-I/Os are embedded on some Atom-based LaCie NASes.
The GPIOs are used to control the LEDs and the hard drive power.

Changes since v3:
- Use request_muxed_region to protect the I/O ports against concurrent
  accesses.

Changes since v2:
- Remove useless NULL setters for driver data.

Changes since v1:
- Enhance the commit message by describing what is a Super-I/O.
- Use self-explanatory names for the GPIO register macros.
- Add a comment to explain the platform device and driver registration.
- Fix gpio_get when GPIO is configured in input mode. I only had
  the hardware to check this mode recently...

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 4b7ba53e96db..349b16160ac9 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -146,6 +146,16 @@ config GPIO_MM_LANTIQ
           (EBU) found on Lantiq SoCs. The gpios are output only as they are
           created by attaching a 16bit latch to the bus.
 
+config GPIO_F7188X
+        tristate "F71882FG and F71889F GPIO support"
+        depends on X86
+        help
+          This option enables support for GPIOs found on Fintek Super-I/O
+          chips F71882FG and F71889F.
+
+          To compile this driver as a module, choose M here: the module will
+          be called f7188x-gpio.
+
 config GPIO_MPC5200
         def_bool y
         depends on PPC_MPC52xx