[PATCH] pwm: add sysfs interface

[H Hartley Sweeten <hartleys@visionengravers.com>]

Add a simple sysfs interface to the PWM framework.

  /sys/class/pwm/
  `-- pwmchipN/          for each PWM chip
      |-- export         (w/o) ask the kernel to export a PWM to userspace
      |-- npwm           (r/o) number of PWM in pwmchipN
      |-- pwmN/          for each exported PWM
      |   |-- duty_ns    (r/w) duty cycle (in nanoseconds)
      |   |-- enable     (r/w) enable/disable PWM
      |   |-- period_ns  (r/w) period (in nanoseconds)
      |   `-- polarity   (r/w) polarity of PWM
      `-- unexport       (w/o) return a PWM to the kernel

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Thierry Reding <thierry.reding@avionic-design.de>
Cc: Lars Poeschel <poeschel@lemonage.de>
---
This is based on previous work by Lars Poeshel.

 drivers/pwm/Kconfig     |   6 +
 drivers/pwm/Makefile    |   1 +
 drivers/pwm/core.c      |  25 +++-
 drivers/pwm/pwm-sysfs.c | 357 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pwm.h     |  28 ++++
 5 files changed, 415 insertions(+), 2 deletions(-)
 create mode 100644 drivers/pwm/pwm-sysfs.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 115b644..61a53b5 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -28,6 +28,12 @@ menuconfig PWM
 
 if PWM
 
+config PWM_SYSFS
+	bool "/sys/class/pwm/... (sysfs interface)"
+	depends on SYSFS
+	help
+	  Say Y here to provide a sysfs interface to control PWMs.
+
 config PWM_AB8500
 	tristate "AB8500 PWM support"
 	depends on AB8500_CORE && ARCH_U8500
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 94ba21e..fb92e1d 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -1,4 +1,5 @@
 obj-$(CONFIG_PWM)		+= core.o
+obj-$(CONFIG_PWM_SYSFS)		+= pwm-sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
 obj-$(CONFIG_PWM_BFIN)		+= pwm-bfin.o
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 32221cb..f67465c 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -274,6 +274,8 @@ int pwmchip_add(struct pwm_chip *chip)
 	if (IS_ENABLED(CONFIG_OF))
 		of_pwmchip_add(chip);
 
+	pwmchip_sysfs_export(chip);
+
 out:
 	mutex_unlock(&pwm_lock);
 	return ret;
@@ -310,6 +312,8 @@ int pwmchip_remove(struct pwm_chip *chip)
 
 	free_pwms(chip);
 
+	pwmchip_sysfs_unexport(chip);
+
 out:
 	mutex_unlock(&pwm_lock);
 	return ret;
@@ -402,10 +406,19 @@ EXPORT_SYMBOL_GPL(pwm_free);
  */
 int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
 {
+	int err;
+
 	if (!pwm || duty_ns < 0 || period_ns <= 0 || duty_ns > period_ns)
 		return -EINVAL;
 
-	return pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
+	err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
+	if (err)
+		return err;
+
+	pwm->duty = duty_ns;
+	pwm->period = period_ns;
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(pwm_config);
 
@@ -418,6 +431,8 @@ EXPORT_SYMBOL_GPL(pwm_config);
  */
 int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
 {
+	int err;
+
 	if (!pwm || !pwm->chip->ops)
 		return -EINVAL;
 
@@ -427,7 +442,13 @@ int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
 	if (test_bit(PWMF_ENABLED, &pwm->flags))
 		return -EBUSY;
 
-	return pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
+	err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
+	if (err)
+		return err;
+
+	pwm->polarity = polarity;
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(pwm_set_polarity);
 
diff --git a/drivers/pwm/pwm-sysfs.c b/drivers/pwm/pwm-sysfs.c
new file mode 100644
index 0000000..6a2bf76
--- /dev/null
+++ b/drivers/pwm/pwm-sysfs.c
@@ -0,0 +1,357 @@
+/*
+ * A simple sysfs interface for the generic PWM framework
+ *
+ * Copyright (C) 2013 H Hartley Sweeten <hsweeten@visionengravers.com>
+ *
+ * Based on previous work by Lars Poeschel <poeschel@lemonage.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/kdev_t.h>
+#include <linux/pwm.h>
+
+struct pwm_export {
+	struct device dev;
+	struct pwm_device *pwm;
+};
+
+static struct pwm_export *dev_to_pwm_export(struct device *dev)
+{
+	return container_of(dev, struct pwm_export, dev);
+}
+
+static struct pwm_device *dev_to_pwm_device(struct device *dev)
+{
+	struct pwm_export *pwm_export = dev_to_pwm_export(dev);
+
+	return pwm_export->pwm;
+}
+
+static ssize_t pwm_period_ns_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	const struct pwm_device *pwm = dev_to_pwm_device(dev);
+
+	return sprintf(buf, "%u\n", pwm->period);
+}
+
+static ssize_t pwm_period_ns_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t size)
+{
+	struct pwm_device *pwm = dev_to_pwm_device(dev);
+	unsigned int val;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	if (val <= pwm->duty)
+		return -EINVAL;
+
+	pwm->period = val;
+
+	if (test_bit(PWMF_ENABLED, &pwm->flags))
+		ret = pwm_config(pwm, pwm->duty, pwm->period);
+
+	return ret ? : size;
+}
+
+static ssize_t pwm_duty_ns_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	const struct pwm_device *pwm = dev_to_pwm_device(dev);
+
+	return sprintf(buf, "%u\n", pwm->duty);
+}
+
+static ssize_t pwm_duty_ns_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t size)
+{
+	struct pwm_device *pwm = dev_to_pwm_device(dev);
+	unsigned int val;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	if (val >= pwm->period)
+		return -EINVAL;
+
+	pwm->duty = val;
+
+	if (test_bit(PWMF_ENABLED, &pwm->flags))
+		ret = pwm_config(pwm, pwm->duty, pwm->period);
+
+	return ret ? : size;
+}
+
+static ssize_t pwm_enable_show(struct device *dev,
+			       struct device_attribute *attr,
+			       char *buf)
+{
+	const struct pwm_device *pwm = dev_to_pwm_device(dev);
+	int enabled = test_bit(PWMF_ENABLED, &pwm->flags);
+
+	return sprintf(buf, "%sabled\n", enabled ? "en" : "dis");
+}
+
+static ssize_t pwm_enable_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t size)
+{
+	struct pwm_device *pwm = dev_to_pwm_device(dev);
+	int val;
+	int ret;
+
+	ret = kstrtoint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	if (val) {
+		ret = pwm_config(pwm, pwm->duty, pwm->period);
+		if (ret)
+			return ret;
+		ret = pwm_enable(pwm);
+	} else {
+		pwm_disable(pwm);
+	}
+
+	return ret ? : size;
+}
+
+static ssize_t pwm_polarity_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	const struct pwm_device *pwm = dev_to_pwm_device(dev);
+	int polarity = (pwm->polarity == PWM_POLARITY_NORMAL);
+
+	return sprintf(buf, "%s\n", polarity ? "normal" : "inversed");
+}
+
+static ssize_t pwm_polarity_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t size)
+{
+	struct pwm_device *pwm = dev_to_pwm_device(dev);
+	enum pwm_polarity polarity;
+	int val;
+	int ret;
+
+	ret = kstrtoint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	switch (val) {
+	case 0:
+		polarity = PWM_POLARITY_NORMAL;
+		break;
+	case 1:
+		polarity = PWM_POLARITY_INVERSED;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	ret = pwm_set_polarity(pwm, polarity);
+
+	return ret ? : size;
+}
+
+static DEVICE_ATTR(period_ns, 0644, pwm_period_ns_show, pwm_period_ns_store);
+static DEVICE_ATTR(duty_ns, 0644, pwm_duty_ns_show, pwm_duty_ns_store);
+static DEVICE_ATTR(enable, 0644, pwm_enable_show, pwm_enable_store);
+static DEVICE_ATTR(polarity, 0644, pwm_polarity_show, pwm_polarity_store);
+
+static struct attribute *pwm_attrs[] = {
+	&dev_attr_period_ns.attr,
+	&dev_attr_duty_ns.attr,
+	&dev_attr_enable.attr,
+	NULL
+};
+
+static struct attribute_group pwm_attr_group = {
+	.attrs		= pwm_attrs,
+};
+
+static void pwm_export_release(struct device *dev)
+{
+	struct pwm_export *pwm_export = dev_to_pwm_export(dev);
+
+	kfree(pwm_export);
+}
+
+static int pwm_export(struct device *dev, struct pwm_device *pwm)
+{
+	struct pwm_export *pwm_export;
+	struct kobject *kobj;
+	int ret;
+
+	if (test_and_set_bit(PWMF_EXPORTED, &pwm->flags))
+		return -EBUSY;
+
+	pwm_export = kzalloc(sizeof(*pwm_export), GFP_KERNEL);
+	if (!pwm_export)
+		return -ENOMEM;
+
+	pwm_export->pwm = pwm;
+
+	pwm_export->dev.release = pwm_export_release;
+	pwm_export->dev.parent = dev;
+	pwm_export->dev.devt = MKDEV(0, 0);
+	dev_set_name(&pwm_export->dev, "pwm%u", pwm->hwpwm);
+	ret = device_register(&pwm_export->dev);
+	if (ret)
+		return ret;
+
+	kobj = &pwm_export->dev.kobj;
+
+	ret = sysfs_create_group(kobj, &pwm_attr_group);
+	if (ret)
+		return ret;
+
+	if (pwm->chip->ops->set_polarity) {
+		ret = sysfs_create_file(kobj, &dev_attr_polarity.attr);
+		if (ret) {
+			sysfs_remove_group(kobj, &pwm_attr_group);
+		}
+	}
+
+	return ret;
+}
+
+static int pwm_unexport_match(struct device *dev, void *data)
+{
+	return dev_to_pwm_device(dev) == data;
+}
+
+static int pwm_unexport(struct device *dev, struct pwm_device *pwm)
+{
+	if (test_and_clear_bit(PWMF_EXPORTED, &pwm->flags)) {
+		struct device *export_dev;
+		struct pwm_export *pwm_export;
+		struct kobject *kobj;
+
+		export_dev = device_find_child(dev, pwm, pwm_unexport_match);
+		pwm_export = dev_to_pwm_export(export_dev);
+		kobj = &pwm_export->dev.kobj;
+
+		if (pwm->chip->ops->set_polarity)
+			sysfs_remove_file(kobj, &dev_attr_polarity.attr);
+
+		sysfs_remove_group(kobj, &pwm_attr_group);
+
+		put_device(&pwm_export->dev);
+		device_unregister(&pwm_export->dev);
+		pwm_put(pwm);
+	}
+	return 0;
+}
+
+static ssize_t pwm_export_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t len)
+{
+	struct pwm_chip *chip = dev_get_drvdata(dev);
+	struct pwm_device *pwm;
+	unsigned int hwpwm;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &hwpwm);
+	if (ret < 0)
+		return ret;
+
+	if (hwpwm >= chip->npwm)
+		return -ENODEV;
+
+	pwm = pwm_request_from_chip(chip, hwpwm, "sysfs");
+	if (IS_ERR(pwm))
+		return PTR_ERR(pwm);
+
+	ret = pwm_export(dev, pwm);
+	if (ret < 0)
+		pwm_put(pwm);
+
+	return ret ? : len;
+}
+
+static ssize_t pwm_unexport_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t len)
+{
+	struct pwm_chip *chip = dev_get_drvdata(dev);
+	unsigned int hwpwm;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &hwpwm);
+	if (ret < 0)
+		return ret;
+
+	if (hwpwm >= chip->npwm)
+		return -ENODEV;
+
+	ret = pwm_unexport(dev, &chip->pwms[hwpwm]);
+
+	return ret ? : len;
+}
+
+static ssize_t pwm_npwm_show(struct device *dev,
+			     struct device_attribute *attr,
+			     char *buf)
+{
+	const struct pwm_chip *chip = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", chip->npwm);
+}
+
+static struct device_attribute pwm_chip_attrs[] = {
+	__ATTR(export, 0200, NULL, pwm_export_store),
+	__ATTR(unexport, 0200, NULL, pwm_unexport_store),
+	__ATTR(npwm, 0444, pwm_npwm_show, NULL),
+	__ATTR_NULL,
+};
+
+static struct class pwm_class = {
+	.name		= "pwm",
+	.owner		= THIS_MODULE,
+	.dev_attrs	= pwm_chip_attrs,
+};
+
+void pwmchip_sysfs_export(struct pwm_chip *chip)
+{
+	chip->dev = device_create(&pwm_class, chip->dev, MKDEV(0, 0), chip,
+				  "pwmchip%d", chip->base);
+}
+
+void pwmchip_sysfs_unexport(struct pwm_chip *chip)
+{
+	if (chip->dev) {
+		put_device(chip->dev);
+		device_unregister(chip->dev);
+	}
+}
+
+static int __init pwm_sysfs_init(void)
+{
+	return class_register(&pwm_class);
+}
+subsys_initcall(pwm_sysfs_init);
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index a4df204..e734ce6 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -76,6 +76,7 @@ enum pwm_polarity {
 enum {
 	PWMF_REQUESTED = 1 << 0,
 	PWMF_ENABLED = 1 << 1,
+	PWMF_EXPORTED = 1 << 2,
 };
 
 struct pwm_device {
@@ -86,7 +87,10 @@ struct pwm_device {
 	struct pwm_chip		*chip;
 	void			*chip_data;
 
+	struct device		*dev;	/* for sysfs export */
 	unsigned int		period; /* in nanoseconds */
+	unsigned int		duty;	/* in nanoseconds */
+	enum pwm_polarity 	polarity;
 };
 
 static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
@@ -100,6 +104,17 @@ static inline unsigned int pwm_get_period(struct pwm_device *pwm)
 	return pwm ? pwm->period : 0;
 }
 
+static inline void pwm_set_duty_cycle(struct pwm_device *pwm, unsigned int duty)
+{
+	if (pwm)
+		pwm->duty = duty;
+}
+
+static inline unsigned int pwm_get_duty_cycle(struct pwm_device *pwm)
+{
+	return pwm ? pwm->duty : 0;
+}
+
 /*
  * pwm_set_polarity - configure the polarity of a PWM signal
  */
@@ -278,4 +293,17 @@ static inline void pwm_add_table(struct pwm_lookup *table, size_t num)
 }
 #endif
 
+#ifdef CONFIG_PWM_SYSFS
+void pwmchip_sysfs_export(struct pwm_chip *chip);
+void pwmchip_sysfs_unexport(struct pwm_chip *chip);
+#else
+static inline void pwmchip_sysfs_export(struct pwm_chip *chip)
+{
+}
+
+static inline void pwmchip_sysfs_unexport(struct pwm_chip *chip)
+{
+}
+#endif /* CONFIG_PWM_SYSFS */
+
 #endif /* __LINUX_PWM_H */
-- 
1.8.1.4