gpio: Add Avionic Design N-bit GPIO expander support

This commit adds a driver for the Avionic Design N-bit GPIO expander.
The expander provides a variable number of GPIO pins with interrupt
support.

Changes in v2:
- allow building the driver as a module
- assign of_node unconditionally
- use linear mapping IRQ domain
- properly cleanup IRQ domain
- add OF device table and annotate device tables
- emulate rising and falling edge triggers
- increase #gpio-cells to 2
- drop support for !OF
- use IS_ENABLED to conditionalize DEBUG_FS code

Changes in v3:
- make IRQ support runtime configurable (interrupt-controller property)
- drop interrupt-controller and #interrupt-cells from DT binding
- add inline to_adnp() function to wrap container_of() macro
- consistently use adnp as name for struct adnp variables
- remove irq_mask_cur and rename irq_mask to irq_enable
- fix a subtle deadlock in adnp_gpio_direction_output()
- remove dynamic allocations from debugfs code
- rename regs to num_regs to avoid confusion
- annotate non-trivial code with comments
- don't acquire mutex in adnp_gpio_get()
- assume NO_IRQ == 0

Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: devicetree-discuss@lists.ozlabs.org
Cc: Linus Walleij <linus.walleij@stericsson.com>
Cc: linux-kernel@vger.kernel.org
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 2f2a3b86b985..bf48c74ba4a0 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -444,6 +444,17 @@ config GPIO_ADP5588_IRQ
           Say yes here to enable the adp5588 to be used as an interrupt
           controller. It requires the driver to be built in the kernel.
 
+config GPIO_ADNP
+        tristate "Avionic Design N-bit GPIO expander"
+        depends on I2C && OF
+        help
+          This option enables support for N GPIOs found on Avionic Design
+          I2C GPIO expanders. The register space will be extended by powers
+          of two, so the controller will need to accomodate for that. For
+          example: if a controller provides 48 pins, 6 registers will be
+          enough to represent all pins, but the driver will assume a
+          register layout for 64 pins (8 registers).
+
 comment "PCI GPIO expanders:"
 
 config GPIO_CS5535