[PATCH v4] GPIO: add support for 74x164 serial-in/parallel-out 8-bit shift register

[Florian Fainelli <florian@openwrt.org>]

From: Miguel Gaio <miguel.gaio@efixo.com>

This patch adds support for generic 74x164 serial-in/parallel-out 8-bits
shift register. This driver can be used as a GPIO output expander.

Signed-off-by: Miguel Gaio <miguel.gaio@efixo.com>
Signed-off-by: Juhos Gabor <juhosg@openwrt.org>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
---
Changes since v1:
- renamed nxp_ to gen_ since this driver is generic to all 74HC164 chips
- added comment on this driver not handling the 74HC164 daisy-chaining
- renamed misused GPIO expanders to Shift registers

Changes since v2:
- rename 74hc164 to 74x164

Changes since v3:
- support daisy-chaining of 74x164 up to 32 gpios

diff --git a/drivers/gpio/74x164.c b/drivers/gpio/74x164.c
new file mode 100644
index 0000000..62e44b7
--- /dev/null
+++ b/drivers/gpio/74x164.c
@@ -0,0 +1,231 @@
+/*
+ *  74Hx164 - Generic serial-in/parallel-out 8-bits shift register GPIO driver
+ *
+ *  Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org>
+ *  Copyright (C) 2010 Miguel Gaio <miguel.gaio@efixo.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/gpio.h>
+#include <linux/bitops.h>
+#include <linux/platform_device.h>
+#include <linux/74x164.h>
+
+#define GEN_74X164_NUM_GPIOS	32
+
+struct gen_74x164_chip {
+	struct device		*parent;
+	struct gpio_chip	gpio_chip;
+	struct mutex		lock;
+	long			mask;
+};
+
+static void gen_74x164_set_value(struct gpio_chip *, unsigned, int);
+
+static struct gen_74x164_chip *gpio_to_chip(struct gpio_chip *gc)
+{
+	return container_of(gc, struct gen_74x164_chip, gpio_chip);
+}
+
+static int gen_74x164_direction_input(struct gpio_chip *gc, unsigned offset)
+{
+	WARN_ON(1);
+	return -EINVAL;
+}
+
+static int gen_74x164_direction_output(struct gpio_chip *gc,
+					unsigned offset, int val)
+{
+	gen_74x164_set_value(gc, offset, val);
+	return 0;
+}
+
+static int gen_74x164_get_value(struct gpio_chip *gc, unsigned offset)
+{
+	struct gen_74x164_chip *chip = gpio_to_chip(gc);
+	int ret;
+
+	mutex_lock(&chip->lock);
+	ret = test_bit(offset, &chip->mask);
+	mutex_unlock(&chip->lock);
+
+	return ret;
+}
+
+static void gen_74x164_set_value(struct gpio_chip *gc,
+				  unsigned offset, int val)
+{
+	struct gen_74x164_chip *chip;
+	struct gen_74x164_platform_data *pdata;
+	long mask;
+	int refresh;
+	int i;
+
+	chip = gpio_to_chip(gc);
+	pdata = chip->parent->platform_data;
+
+	mutex_lock(&chip->lock);
+	if (val)
+		refresh = (test_and_set_bit(offset, &chip->mask) != val);
+	else
+		refresh = (test_and_clear_bit(offset, &chip->mask) != val);
+
+	if (refresh) {
+		mask = chip->mask;
+		for (i = pdata->ngpio - 1; i >= 0; --i) {
+			gpio_set_value(pdata->gpio_pin_data,
+							test_bit(i, &mask));
+			gpio_set_value(pdata->gpio_pin_clk, 1);
+			gpio_set_value(pdata->gpio_pin_clk, 0);
+		}
+	}
+	mutex_unlock(&chip->lock);
+}
+
+static int __devinit gen_74x164_probe(struct platform_device *pdev)
+{
+	struct gen_74x164_platform_data *pdata;
+	struct gen_74x164_chip *chip;
+	struct gpio_chip *gc;
+	int err;
+
+	pdata = pdev->dev.platform_data;
+	if (pdata == NULL) {
+		dev_dbg(&pdev->dev, "no platform data specified\n");
+		return -EINVAL;
+	}
+
+	if (pdata->ngpio > GEN_74X164_NUM_GPIOS) {
+		dev_err(&pdev->dev, "invalid gpio count %u\n", pdata->ngpio);
+		return -EINVAL;
+	}
+
+	chip = kzalloc(sizeof(struct gen_74x164_chip), GFP_KERNEL);
+	if (chip == NULL) {
+		dev_err(&pdev->dev, "no memory for private data\n");
+		return -ENOMEM;
+	}
+
+	err = gpio_request(pdata->gpio_pin_clk, dev_name(&pdev->dev));
+	if (err) {
+		dev_err(&pdev->dev, "unable to claim gpio %u, err=%d\n",
+			pdata->gpio_pin_clk, err);
+		goto err_free_chip;
+	}
+
+	err = gpio_request(pdata->gpio_pin_data, dev_name(&pdev->dev));
+	if (err) {
+		dev_err(&pdev->dev, "unable to claim gpio %u, err=%d\n",
+			pdata->gpio_pin_data, err);
+		goto err_free_clk;
+	}
+
+	err = gpio_direction_output(pdata->gpio_pin_clk, 0);
+	if (err) {
+		dev_err(&pdev->dev,
+			"unable to set direction of gpio %u, err=%d\n",
+			pdata->gpio_pin_clk, err);
+		goto err_free_data;
+	}
+
+	err = gpio_direction_output(pdata->gpio_pin_data, 0);
+	if (err) {
+		dev_err(&pdev->dev,
+			"unable to set direction of gpio %u, err=%d\n",
+			pdata->gpio_pin_data, err);
+		goto err_free_data;
+	}
+
+	chip->parent = &pdev->dev;
+	mutex_init(&chip->lock);
+
+	gc = &chip->gpio_chip;
+
+	gc->direction_input  = gen_74x164_direction_input;
+	gc->direction_output = gen_74x164_direction_output;
+	gc->get = gen_74x164_get_value;
+	gc->set = gen_74x164_set_value;
+	gc->can_sleep = 1;
+
+	gc->base = pdata->gpio_base;
+	gc->ngpio = pdata->ngpio;
+	gc->label = dev_name(chip->parent);
+	gc->dev = chip->parent;
+	gc->owner = THIS_MODULE;
+
+	err = gpiochip_add(&chip->gpio_chip);
+	if (err) {
+		dev_err(&pdev->dev, "unable to add gpio chip, err=%d\n", err);
+		goto err_free_data;
+	}
+
+	platform_set_drvdata(pdev, chip);
+	return 0;
+
+err_free_data:
+	gpio_free(pdata->gpio_pin_data);
+err_free_clk:
+	gpio_free(pdata->gpio_pin_clk);
+err_free_chip:
+	kfree(chip);
+	return err;
+}
+
+static int gen_74x164_remove(struct platform_device *pdev)
+{
+	struct gen_74x164_chip *chip = platform_get_drvdata(pdev);
+	struct gen_74x164_platform_data *pdata = pdev->dev.platform_data;
+
+	if (chip) {
+		int err;
+
+		err = gpiochip_remove(&chip->gpio_chip);
+		if (err) {
+			dev_err(&pdev->dev,
+				"unable to remove gpio chip, err=%d\n",
+				err);
+			return err;
+		}
+
+		gpio_free(pdata->gpio_pin_clk);
+		gpio_free(pdata->gpio_pin_data);
+
+		kfree(chip);
+		platform_set_drvdata(pdev, NULL);
+	}
+
+	return 0;
+}
+
+static struct platform_driver gen_74x164_driver = {
+	.probe		= gen_74x164_probe,
+	.remove		= __devexit_p(gen_74x164_remove),
+	.driver = {
+		.name	= GEN_74X164_DRIVER_NAME,
+		.owner	= THIS_MODULE,
+	},
+};
+
+static int __init gen_74x164_init(void)
+{
+	return platform_driver_register(&gen_74x164_driver);
+}
+subsys_initcall(gen_74x164_init);
+
+static void __exit gen_74x164_exit(void)
+{
+	platform_driver_unregister(&gen_74x164_driver);
+}
+module_exit(gen_74x164_exit);
+
+MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
+MODULE_AUTHOR("Miguel Gaio <miguel.gaio@efixo.com>");
+MODULE_DESCRIPTION("GPIO expander driver for 74X164 8-bits shift register");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" GEN_74X164_DRIVER_NAME);
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 510aa20..fc82c23 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -361,4 +361,13 @@ config GPIO_JANZ_TTL
 	  This driver provides support for driving the pins in output
 	  mode only. Input mode is not supported.
 
+comment "Shift registers:"
+
+config GPIO_74X164
+       tristate "74x164 serial-in/parallel-out 8-bits shift register"
+       help
+         Platform driver for 74x164 compatible serial-in/parallel-out
+	 8-outputs shift registers. This driver can be used to provide access
+	 to more gpio outputs.
+
 endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index fc6019d..60456a4 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_GPIO_MAX7301)	+= max7301.o
 obj-$(CONFIG_GPIO_MAX732X)	+= max732x.o
 obj-$(CONFIG_GPIO_MC33880)	+= mc33880.o
 obj-$(CONFIG_GPIO_MCP23S08)	+= mcp23s08.o
+obj-$(CONFIG_GPIO_74X164)	+= 74x164.o
 obj-$(CONFIG_GPIO_PCA953X)	+= pca953x.o
 obj-$(CONFIG_GPIO_PCF857X)	+= pcf857x.o
 obj-$(CONFIG_GPIO_PL061)	+= pl061.o
diff --git a/include/linux/74x164.h b/include/linux/74x164.h
new file mode 100644
index 0000000..b58b159
--- /dev/null
+++ b/include/linux/74x164.h
@@ -0,0 +1,23 @@
+/*
+ *  74x164 - Serial-in/parallel-out 8-bits shift register
+ *
+ *  Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ */
+
+#ifndef __74X164_H
+#define __74X164_H
+
+#define GEN_74X164_DRIVER_NAME "74x164"
+
+struct gen_74x164_platform_data {
+	unsigned	gpio_base;
+	unsigned	ngpio;
+	unsigned	gpio_pin_data;
+	unsigned	gpio_pin_clk;
+};
+
+#endif /* __74x164_H */