Message-Id: <1364997536-9246-1-git-send-email-larsi@wh2.tu-dresden.de>
Date:	Wed,  3 Apr 2013 15:58:55 +0200
From:	Lars Poeschel <larsi@....tu-dresden.de>
To:	poeschel@...onage.de, thierry.reding@...onic-design.de,
	rob@...dley.net, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: [PATCH v1] pwm: add sysfs interface

From: Lars Poeschel <poeschel@...onage.de>

This adds a simple sysfs interface to the pwm subsystem. It is
heavily inspired by the gpio sysfs interface.

        /sys/class/pwm
                /export ... asks the kernel to export a PWM to userspace
                /unexport ... to return a PWM to the kernel
            /pwmN ... for each exported PWM #N
            /duty_ns ... r/w, length of duty portion
            /period_ns ... r/w, length of the pwm period
            /polarity ... r/w, normal(0) or inverse(1) polarity
                               only created if driver supports it
            /run ... r/w, write 1 to start and 0 to stop the pwm
        /pwmchipN ... for each pwmchip; #N is its first PWM
            /base ... (r/o) same as N
            /ngpio ... (r/o) number of PWM; numbered N .. MAX_PWMS

Signed-off-by: Lars Poeschel <poeschel@...onage.de>
---
since PATCH RFC:

* updated documentation
* added ABI doc
* use default group functionality when exposing files to userspace

 create mode 100644 Documentation/ABI/testing/sysfs-class-pwm

diff --git a/Documentation/ABI/testing/sysfs-class-pwm b/Documentation/ABI/testing/sysfs-class-pwm
new file mode 100644
index 0000000..e9be1a3
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-pwm
@@ -0,0 +1,37 @@
+What:		/sys/class/pwm/
+Date:		March 2013
+KernelVersion:	3.11
+Contact:	Lars Poeschel <poeschel@...onage.de>
+Description:
+
+  The sysfs interface for PWM is selectable as a Kconfig option.
+  If a driver successfully probed a pwm chip, it appears at
+  /sys/class/pwm/pwmchipN/ where N is the number of it's first PWM channel. A
+  single driver may probe multiple chips. PWMs are identified as they are
+  inside the kernel, using integers in the range 0..MAX_PWMS. To use an
+  individual PWM, you have to explicitly export it by writing it's kernel
+  global number into the /sys/class/pwm/export file. Write it's number to
+  /sys/class/pwm/unexport to make the pwm available for other uses.
+  After a PWM channel is exported, it is available under
+  /sys/class/pwm/pwmN/. Under this directory you can set the parameters for
+  this PWM channel and at least let it start running.
+  See below for the parameters.
+  It is recommended to set the period_ns at first and the duty_ns after that.
+
+  See Documentation/pwm.txt for more information.
+
+Directory structure:
+
+	/sys/class/pwm
+		/export ... asks the kernel to export a PWM to userspace
+		/unexport ... to return a PWM to the kernel
+		/pwmN ... for each exported PWM #N
+			/duty_ns ... r/w, length of duty portion
+			/period_ns ... r/w, length of the pwm period
+			/polarity ... r/w, normal(0) or inverse(1) polarity
+					only created if driver supports it
+			/run ... r/w, write 1 to start and 0 to stop the pwm
+		/pwmchipN ... for each pwmchip; #N is its first PWM
+			/base ... (r/o) same as N
+			/ngpio ... (r/o) number of PWM; numbered N .. MAX_PWMS
+
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 7d2b4c9..b349d16 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -45,6 +45,52 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
 
 To start/stop toggling the PWM output use pwm_enable()/pwm_disable().
 
+Using PWMs with the sysfs interface
+-----------------------------------
+
+You have to enable CONFIG_PWM_SYSFS in your kernel configuration to use
+the sysfs interface. It is exposed at /sys/class/pwm/. If there are pwm
+drivers loaded and these drivers successfully probed a chip, this chip
+is exported as pwmchipX . Note that a single driver can probe multiple chips.
+Inside the directory you can read these properties:
+
+base - This is the linux global start where the chips pwm channels get
+exposed.
+
+npwm - This is the number of pwm channels this chip supports.
+
+If you want to start using a pwm channel with sysfs first you have to
+export it. If you are finished with it and want to free the pwm for other
+uses, you can unexport it:
+
+export - Write the global pwm channel number to this file to start using
+the channel with sysfs.
+
+unexport - Write the global pwm channel number of the channel you are finshed
+with to this file to make the channel available for other uses.
+
+Once a pwm is exported a pwmX (X ranging from 0 to MAX_PWMS) directory appears
+with the following read/write properties inside to control the pwm:
+
+duty_ns - Write the number of nanoseconds the active portion of the pwm period
+should last to this file. This can not be longer than the period_ns.
+
+period_ns - Write the length of the pwm period in nanoseconds to this file.
+This includes the active and inactive portion of the pwm period and can not
+be smaller than duty_ns.
+
+polarity - The normal behaviour is to put out a high for the active portion of
+the pwm period. Write a 1 to this file to inverse the signal and output a low
+on the active portion. Write a 0 to switch back to the normal behaviour. The
+polarity can only be changed if the pwm is not running. This file is only
+visible if the underlying driver/device supports changing the polarity.
+
+run - Write a 1 to this file to start the pwm signal generation, write a 0 to
+stop it. Set your desired period_ns, duty_ns and polarity before starting the
+pwm.
+
+It is recommend to set the period_ns at first and duty_ns after that.
+
 Implementing a PWM driver
 -------------------------
 
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index e513cd9..2f4200a 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -28,6 +28,18 @@ menuconfig PWM
 
 if PWM
 
+config PWM_SYSFS
+	bool "/sys/class/pwm/... (sysfs interface)"
+	depends on SYSFS
+	help
+	  Say Y here to use a sysfs interface to control PWMs.
+
+	  For every instance of an PWM capable device there is a pwmchipX
+	  directory exported to /sys/class/pwm. If you want to use a PWM, you
+	  have to export it to sysfs, which is done by writing the number into
+	  /sys/class/pwm/export. After that /sys/class/pwm/pwmX is ready to be
+	  used.
+
 config PWM_AB8500
 	tristate "AB8500 PWM support"
 	depends on AB8500_CORE && ARCH_U8500
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 903138b..0f2e40c 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -30,8 +30,6 @@
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 
-#define MAX_PWMS 1024
-
 /* flags in the third cell of the DT PWM specifier */
 #define PWM_SPEC_POLARITY	(1 << 0)
 
@@ -42,6 +40,465 @@ static LIST_HEAD(pwm_chips);
 static DECLARE_BITMAP(allocated_pwms, MAX_PWMS);
 static RADIX_TREE(pwm_tree, GFP_KERNEL);
 
+
+#ifdef CONFIG_PWM_SYSFS
+
+/* lock protects against unexport_pwm() being called while
+ * sysfs files are active.
+ */
+static DEFINE_MUTEX(sysfs_lock);
+static struct class pwm_class;
+static struct pwm_device *pwm_table[MAX_PWMS];
+
+/*
+ * /sys/class/pwm/pwm... only for PWMs that are exported
+ *   /polarity
+ *      * only visible if the underlying driver has registered a
+ *        set_polarity function
+ *      * always readable
+ *      * may be written as "1" for inverted polarity or "0" for
+ *        normal polarity
+ *      * can only be written if PWM is not running
+ *   /period_ns
+ *      * always readable
+ *      * write with desired pwm period in nanoseconds
+ *      * may return with error depending on duty_ns
+ *   /duty_ns
+ *      * always readable
+ *      * write with desired duty portion in nanoseconds
+ *      * may return with error depending on period_ns
+ *   /run
+ *      * always readable
+ *      * write with "1" to start generating pwm signal, "0" to stop it
+ */
+static ssize_t pwm_polarity_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	const struct pwm_device *pwm = dev_get_drvdata(dev);
+	ssize_t	status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_EXPORT, &pwm->flags))
+		status = -EIO;
+	else
+		status = sprintf(buf, "%d\n", pwm->polarity);
+
+	mutex_unlock(&sysfs_lock);
+
+	return status;
+}
+
+static ssize_t pwm_polarity_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct pwm_device *pwm = dev_get_drvdata(dev);
+	ssize_t status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_EXPORT, &pwm->flags))
+		status = -EIO;
+	else {
+		long value;
+
+		status = kstrtol(buf, 0, &value);
+		if (status == 0) {
+			if (value == 0) {
+				if (pwm->polarity == PWM_POLARITY_NORMAL)
+					goto fail_unlock;
+				status = pwm_set_polarity(pwm,
+							PWM_POLARITY_NORMAL);
+			} else {
+				if (pwm->polarity == PWM_POLARITY_INVERSED)
+					goto fail_unlock;
+				status = pwm_set_polarity(pwm,
+							PWM_POLARITY_INVERSED);
+			}
+		}
+	}
+
+fail_unlock:
+	mutex_unlock(&sysfs_lock);
+	return status ? : size;
+}
+
+static const DEVICE_ATTR(polarity, 0644,
+		pwm_polarity_show, pwm_polarity_store);
+
+
+static ssize_t pwm_period_ns_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	const struct pwm_device *pwm = dev_get_drvdata(dev);
+	ssize_t	status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_EXPORT, &pwm->flags))
+		status = -EIO;
+	else
+		status = sprintf(buf, "%d\n", pwm->period);
+
+	mutex_unlock(&sysfs_lock);
+
+	return status;
+}
+
+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_get_drvdata(dev);
+	ssize_t status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_EXPORT, &pwm->flags))
+		status = -EIO;
+	else {
+		long value;
+
+		status = kstrtol(buf, 0, &value);
+		if (status == 0) {
+			if (pwm->duty < 0)
+				pwm->period = value;
+			else
+				status = pwm_config(pwm, pwm->duty, value);
+		}
+	}
+
+	mutex_unlock(&sysfs_lock);
+
+	return status ? : size;
+}
+
+static ssize_t pwm_duty_ns_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	const struct pwm_device *pwm = dev_get_drvdata(dev);
+	ssize_t	status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_EXPORT, &pwm->flags))
+		status = -EIO;
+	else
+		status = sprintf(buf, "%d\n", pwm->duty);
+
+	mutex_unlock(&sysfs_lock);
+
+	return status;
+}
+
+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_get_drvdata(dev);
+	ssize_t status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_EXPORT, &pwm->flags))
+		status = -EIO;
+	else {
+		long value;
+
+		status = kstrtol(buf, 0, &value);
+		if (status == 0) {
+			if (pwm->period <= 0)
+				pwm->duty = value;
+			else
+				status = pwm_config(pwm, value, pwm->period);
+		}
+	}
+
+	mutex_unlock(&sysfs_lock);
+
+	return status ? : size;
+}
+
+static ssize_t pwm_run_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	const struct pwm_device *pwm = dev_get_drvdata(dev);
+	ssize_t	status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_EXPORT, &pwm->flags))
+		status = -EIO;
+	else
+		status = sprintf(buf, "%d\n",
+				!!test_bit(PWMF_ENABLED, &pwm->flags));
+
+	mutex_unlock(&sysfs_lock);
+
+	return status;
+}
+
+static ssize_t pwm_run_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct pwm_device *pwm = dev_get_drvdata(dev);
+	ssize_t	status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_EXPORT, &pwm->flags))
+		status = -EIO;
+	else {
+		long		value;
+
+		status = kstrtol(buf, 0, &value);
+		if (status == 0) {
+			if (value)
+				status = pwm_enable(pwm);
+			else
+				pwm_disable(pwm);
+		}
+	}
+
+	mutex_unlock(&sysfs_lock);
+
+	return status ? : size;
+}
+
+static struct device_attribute pwm_dev_attrs[] = {
+	__ATTR(period_ns, 0644, pwm_period_ns_show, pwm_period_ns_store),
+	__ATTR(duty_ns, 0644, pwm_duty_ns_show, pwm_duty_ns_store),
+	__ATTR(run, 0644, pwm_run_show, pwm_run_store),
+	__ATTR_NULL,
+};
+
+/*
+ * /sys/class/pwm/pwmchipN/
+ *   /base ... matching pwm_chip.base (N)
+ *   /ngpio ... matching pwm_chip.npwm
+ */
+
+static ssize_t chip_base_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	const struct pwm_chip	*chip = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", chip->base);
+}
+
+static ssize_t chip_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 int pwm_export(struct pwm_device *pwm)
+{
+	struct device *dev;
+	int status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(PWMF_REQUESTED, &pwm->flags) ||
+		test_bit(PWMF_EXPORT, &pwm->flags)) {
+		pr_debug("pwm %d unavailable (requested=%d, exported=%d)\n",
+			pwm->pwm,
+			test_bit(PWMF_REQUESTED, &pwm->flags),
+			test_bit(PWMF_EXPORT, &pwm->flags));
+
+		status = -EPERM;
+		goto fail_unlock;
+	}
+
+	pwm_class.class_attrs = NULL;
+	pwm_class.dev_attrs = pwm_dev_attrs;
+	dev = device_create(&pwm_class, pwm->chip->dev, MKDEV(0, 0),
+			pwm, "pwm%u", pwm->pwm);
+	if (IS_ERR(dev)) {
+		status = PTR_ERR(dev);
+		goto fail_unlock;
+	}
+
+	if (pwm->chip->ops->set_polarity) {
+		status = device_create_file(dev, &dev_attr_polarity);
+		if (status)
+			goto fail_unregister_device;
+	}
+
+	set_bit(PWMF_EXPORT, &pwm->flags);
+	mutex_unlock(&sysfs_lock);
+	return 0;
+
+fail_unregister_device:
+	device_unregister(dev);
+fail_unlock:
+	mutex_unlock(&sysfs_lock);
+	return status;
+}
+
+static int match_export(struct device *dev, void *data)
+{
+	return dev_get_drvdata(dev) == data;
+}
+
+/*
+ * /sys/class/pwm/export ... write-only
+ *	integer N ... number of pwm to export (full access)
+ * /sys/class/pwm/unexport ... write-only
+ *	integer N ... number of pwm to unexport
+ */
+static ssize_t export_store(struct class *class,
+				struct class_attribute *attr,
+				const char *buf, size_t len)
+{
+	long pwm;
+	int status;
+	struct pwm_device *dev;
+	struct pwm_chip *chip;
+
+	status = kstrtol(buf, 0, &pwm);
+	if (status < 0)
+		goto done;
+
+	if (!pwm_is_valid(pwm) || !pwm_table[pwm]) {
+		status = -ENODEV;
+		goto done;
+	}
+	chip = pwm_table[pwm]->chip;
+	if (!chip) {
+		status = -ENODEV;
+		goto done;
+	}
+	dev = pwm_request_from_chip(chip, pwm - chip->base, "sysfs");
+	if (IS_ERR(dev)) {
+		status = -ENODEV;
+		goto done;
+	}
+	status = pwm_export(dev);
+	if (status < 0)
+		pwm_free(dev);
+done:
+	if (status)
+		pr_debug("%s: status %d\n", __func__, status);
+	return status ? : len;
+}
+
+static ssize_t unexport_store(struct class *class,
+				struct class_attribute *attr,
+				const char *buf, size_t len)
+{
+	long pwm;
+	int status;
+	struct pwm_device *dev;
+	struct device *d;
+
+	status = kstrtol(buf, 0, &pwm);
+	if (status < 0)
+		goto done;
+
+	status = -EINVAL;
+
+	/* reject bogus pwms */
+	if (!pwm_is_valid(pwm))
+		goto done;
+
+	dev = pwm_table[pwm];
+	if (dev && test_and_clear_bit(PWMF_EXPORT, &dev->flags)) {
+		d = class_find_device(&pwm_class, NULL, dev, match_export);
+		if (d)
+			device_unregister(d);
+		status = 0;
+		pwm_put(dev);
+	}
+done:
+	if (status)
+		pr_debug("%s: status %d\n", __func__, status);
+	return status ? : len;
+}
+
+static struct class_attribute pwmchip_class_attrs[] = {
+	__ATTR(export, 0200, NULL, export_store),
+	__ATTR(unexport, 0200, NULL, unexport_store),
+	__ATTR_NULL,
+};
+
+static struct device_attribute pwmchip_dev_attrs[] = {
+	__ATTR(base, 0444, chip_base_show, NULL),
+	__ATTR(npwm, 0444, chip_npwm_show, NULL),
+	__ATTR_NULL,
+};
+
+static struct class pwm_class = {
+	.name =		"pwm",
+	.owner =	THIS_MODULE,
+	.class_attrs =	pwmchip_class_attrs,
+	.dev_attrs =	pwmchip_dev_attrs,
+};
+
+static int pwmchip_export(struct pwm_chip *chip)
+{
+	struct device *dev;
+
+	mutex_lock(&sysfs_lock);
+	pwm_class.class_attrs = pwmchip_class_attrs;
+	pwm_class.dev_attrs = pwmchip_dev_attrs;
+	dev = device_create(&pwm_class, chip->dev, MKDEV(0, 0), chip,
+				"pwmchip%d", chip->base);
+
+	chip->exported = (!IS_ERR(dev));
+	mutex_unlock(&sysfs_lock);
+
+	if (chip->exported)
+		return 0;
+
+	return PTR_ERR(dev);
+}
+
+static void pwmchip_unexport(struct pwm_chip *chip)
+{
+	int status, i;
+	struct device *dev;
+
+	mutex_lock(&sysfs_lock);
+	dev = class_find_device(&pwm_class, NULL, chip, match_export);
+	if (dev) {
+		put_device(dev);
+		device_unregister(dev);
+		for (i = chip->base; i < chip->base + chip->npwm; i++)
+			pwm_table[i] = NULL;
+		chip->exported = 0;
+		status = 0;
+	} else
+		status = -ENODEV;
+	mutex_unlock(&sysfs_lock);
+
+	if (status)
+		pr_debug("%s: pwm chip status %d\n", __func__, status);
+}
+
+static int __init pwmlib_sysfs_init(void)
+{
+	int status;
+
+	status = class_register(&pwm_class);
+
+	return status;
+}
+postcore_initcall(pwmlib_sysfs_init);
+
+#else
+static inline int pwmchip_export(struct pwm_chip *chip)
+{
+	return 0;
+}
+
+static inline void pwmchip_unexport(struct pwm_chip *chip)
+{
+}
+
+#endif /* CONFIG_PWM_SYSFS */
+
+
 static struct pwm_device *pwm_to_device(unsigned int pwm)
 {
 	return radix_tree_lookup(&pwm_tree, pwm);
@@ -77,8 +534,10 @@ static void free_pwms(struct pwm_chip *chip)
 	for (i = 0; i < chip->npwm; i++) {
 		struct pwm_device *pwm = &chip->pwms[i];
 		radix_tree_delete(&pwm_tree, pwm->pwm);
+#ifdef CONFIG_PWM_SYSFS
+		pwm_table[i + chip->base]->chip = NULL;
+#endif
 	}
-
 	bitmap_clear(allocated_pwms, chip->base, chip->npwm);
 
 	kfree(chip->pwms);
@@ -258,6 +717,9 @@ int pwmchip_add(struct pwm_chip *chip)
 		pwm->chip = chip;
 		pwm->pwm = chip->base + i;
 		pwm->hwpwm = i;
+#ifdef CONFIG_PWM_SYSFS
+		pwm_table[i + chip->base] = pwm;
+#endif
 
 		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
 	}
@@ -272,6 +734,8 @@ int pwmchip_add(struct pwm_chip *chip)
 	if (IS_ENABLED(CONFIG_OF))
 		of_pwmchip_add(chip);
 
+	ret = pwmchip_export(chip);
+
 out:
 	mutex_unlock(&pwm_lock);
 	return ret;
@@ -307,6 +771,7 @@ int pwmchip_remove(struct pwm_chip *chip)
 		of_pwmchip_remove(chip);
 
 	free_pwms(chip);
+	pwmchip_unexport(chip);
 
 out:
 	mutex_unlock(&pwm_lock);
@@ -400,10 +865,19 @@ EXPORT_SYMBOL_GPL(pwm_free);
  */
 int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
 {
+	int status;
+
 	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);
+	status = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
+#ifdef CONFIG_PWM_SYSFS
+	if (status == 0) {
+		pwm->period = period_ns;
+		pwm->duty = duty_ns;
+	}
+#endif
+	return status;
 }
 EXPORT_SYMBOL_GPL(pwm_config);
 
@@ -416,6 +890,8 @@ EXPORT_SYMBOL_GPL(pwm_config);
  */
 int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
 {
+	int status;
+
 	if (!pwm || !pwm->chip->ops)
 		return -EINVAL;
 
@@ -425,7 +901,12 @@ 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);
+	status = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
+#ifdef CONFIG_PWM_SYSFS
+	if (!status)
+		pwm->polarity = polarity;
+#endif
+	return status;
 }
 EXPORT_SYMBOL_GPL(pwm_set_polarity);
 
@@ -749,6 +1230,9 @@ static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
 		if (test_bit(PWMF_ENABLED, &pwm->flags))
 			seq_printf(s, " enabled");
 
+		if (test_bit(PWMF_EXPORT, &pwm->flags))
+			seq_printf(s, " sysfs_exported");
+
 		seq_printf(s, "\n");
 	}
 }
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 6d661f3..afc22c6 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -4,10 +4,27 @@
 #include <linux/err.h>
 #include <linux/of.h>
 
+#define MAX_PWMS 1024
+
 struct pwm_device;
 struct seq_file;
 
 #if IS_ENABLED(CONFIG_PWM) || IS_ENABLED(CONFIG_HAVE_PWM)
+
+/*
+ * "valid" PWM numbers are nonnegative and may be passed to
+ * setup routines like pwm_get().  only some valid numbers
+ * can successfully be requested and used.
+ *
+ * Invalid PWM numbers are useful for indicating no-such-PWM in
+ * platform data and other tables.
+ */
+
+static inline bool pwm_is_valid(int number)
+{
+	return number >= 0 && number < MAX_PWMS;
+}
+
 /*
  * pwm_request - request a PWM device
  */
@@ -75,7 +92,8 @@ enum pwm_polarity {
 
 enum {
 	PWMF_REQUESTED = 1 << 0,
-	PWMF_ENABLED = 1 << 1,
+	PWMF_ENABLED = 1 << 1, /* set running via /sys/class/pwm/pwmX/run */
+	PWMF_EXPORT = 1 << 2, /* exported via /sys/class/pwm/export */
 };
 
 struct pwm_device {
@@ -87,6 +105,10 @@ struct pwm_device {
 	void			*chip_data;
 
 	unsigned int		period; /* in nanoseconds */
+#ifdef CONFIG_PWM_SYSFS
+	unsigned int		duty; /* in nanoseconds */
+	enum pwm_polarity	polarity;
+#endif
 };
 
 static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
@@ -159,6 +181,9 @@ struct pwm_chip {
 	struct pwm_device *	(*of_xlate)(struct pwm_chip *pc,
 					    const struct of_phandle_args *args);
 	unsigned int		of_pwm_n_cells;
+#ifdef CONFIG_PWM_SYSFS
+	unsigned		exported:1;
+#endif
 };
 
 #if IS_ENABLED(CONFIG_PWM)
-- 
1.7.10.4

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