[PATCH v3 3/4] gpiolib: Add support for GPIO "hog" nodes

[Andrey Smirnov <andrew.smirnov@gmail.com>]

Add code to support 'gpio-hog' nodes used in some .dts files in Linux
kernel.

Cc: cphealy@gmail.com
Cc: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---
 drivers/gpio/gpiolib.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 95 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 28f6a5e..a3e17ad 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -5,6 +5,7 @@
 #include <command.h>
 #include <complete.h>
 #include <gpio.h>
+#include <of_gpio.h>
 #include <errno.h>
 #include <malloc.h>
 
@@ -304,6 +305,99 @@ static int gpiochip_find_base(int start, int ngpio)
 	return base;
 }
 
+static int of_hog_gpio(struct device_node *np, struct gpio_chip *chip,
+		       unsigned int idx)
+{
+	struct device_node *chip_np = chip->dev->device_node;
+	unsigned long flags = 0;
+	u32 gpio_cells, gpio_num, gpio_flags;
+	int ret, gpio;
+	const char *name = NULL;
+
+	ret = of_property_read_u32(chip_np, "#gpio-cells", &gpio_cells);
+	if (ret)
+		return ret;
+
+	/*
+	 * Support for GPIOs that don't have #gpio-cells set to 2 is
+	 * not implemented
+	 */
+	if (WARN_ON(gpio_cells != 2))
+		return -ENOTSUPP;
+
+	ret = of_property_read_u32_index(np, "gpios", idx * gpio_cells,
+					 &gpio_num);
+	if (ret)
+		return ret;
+
+	ret = of_property_read_u32_index(np, "gpios", idx * gpio_cells + 1,
+					 &gpio_flags);
+	if (ret)
+		return ret;
+
+	if (gpio_flags & OF_GPIO_ACTIVE_LOW)
+		flags |= GPIOF_ACTIVE_LOW;
+
+	gpio = gpio_get_num(chip->dev, gpio_num);
+	if (ret == -EPROBE_DEFER)
+		return ret;
+
+	if (ret < 0) {
+		dev_err(chip->dev, "unable to get gpio %u\n", gpio_num);
+		return ret;
+	}
+
+
+	/*
+	 * Note that, in order to be compatible with Linux, the code
+	 * below interprets 'output-high' as to mean 'output-active'.
+	 * That is, when processed for active-low GPIO, it will result
+	 * in output being asserted logically 'active', but physically
+	 * 'low'.
+	 *
+	 * Conversely it means that specifying 'output-low' for
+	 * 'active-low' GPIO would result in 'high' level observed on
+	 * the corresponding pin
+	 *
+	 */
+	if (of_property_read_bool(np, "input"))
+		flags |= GPIOF_DIR_IN;
+	else if (of_property_read_bool(np, "output-low"))
+		flags |= GPIOF_OUT_INIT_INACTIVE;
+	else if (of_property_read_bool(np, "output-high"))
+		flags |= GPIOF_OUT_INIT_ACTIVE;
+	else
+		return -EINVAL;
+
+	of_property_read_string(np, "line-name", &name);
+
+	return gpio_request_one(gpio, flags, name);
+}
+
+static int of_gpiochip_scan_hogs(struct gpio_chip *chip)
+{
+	struct device_node *np;
+	int ret, i;
+
+	for_each_available_child_of_node(chip->dev->device_node, np) {
+		if (!of_property_read_bool(np, "gpio-hog"))
+			continue;
+
+		for (ret = 0, i = 0;
+		     !ret;
+		     ret = of_hog_gpio(np, chip, i), i++)
+			;
+		/*
+		 * We ignore -EOVERFLOW because it serves us as an
+		 * indicator that there's no more GPIOs to handle.
+		 */
+		if (ret < 0 && ret != -EOVERFLOW)
+			return ret;
+	}
+
+	return 0;
+}
+
 int gpiochip_add(struct gpio_chip *chip)
 {
 	int base, i;
@@ -322,7 +416,7 @@ int gpiochip_add(struct gpio_chip *chip)
 	for (i = chip->base; i < chip->base + chip->ngpio; i++)
 		gpio_desc[i].chip = chip;
 
-	return 0;
+	return of_gpiochip_scan_hogs(chip);
 }
 
 void gpiochip_remove(struct gpio_chip *chip)
-- 
2.9.4


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