pwm: Add sysfs interface

Add a simple sysfs interface to the generic PWM framework.

  /sys/class/pwm/
  `-- pwmchipN/           for each PWM chip
      |-- export          (w/o) ask the kernel to export a PWM channel
      |-- npwm            (r/o) number of PWM channels in this PWM chip
      |-- pwmX/           for each exported PWM channel
      |   |-- duty_cycle  (r/w) duty cycle (in nanoseconds)
      |   |-- enable      (r/w) enable/disable PWM
      |   |-- period      (r/w) period (in nanoseconds)
      |   `-- polarity    (r/w) polarity of PWM (normal/inversed)
      `-- unexport        (w/o) return a PWM channel to the kernel

Based on work by Lars Poeschel.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Lars Poeschel <poeschel@lemonage.de>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Rob Landley <rob@landley.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

7 files changed, 524 insertions, 3 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-pwm b/Documentation/ABI/testing/sysfs-class-pwm
new file mode 100644
index 000000000000..c479d77b67c5
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-pwm
@@ -0,0 +1,79 @@
+What:           /sys/class/pwm/
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                The pwm/ class sub-directory belongs to the Generic PWM
+                Framework and provides a sysfs interface for using PWM
+                channels.
+
+What:           /sys/class/pwm/pwmchipN/
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                A /sys/class/pwm/pwmchipN directory is created for each
+                probed PWM controller/chip where N is the base of the
+                PWM chip.
+
+What:           /sys/class/pwm/pwmchipN/npwm
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                The number of PWM channels supported by the PWM chip.
+
+What:           /sys/class/pwm/pwmchipN/export
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                Exports a PWM channel from the PWM chip for sysfs control.
+                Value is between 0 and /sys/class/pwm/pwmchipN/npwm - 1.
+
+What:           /sys/class/pwm/pwmchipN/unexport
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                Unexports a PWM channel.
+
+What:           /sys/class/pwm/pwmchipN/pwmX
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                A /sys/class/pwm/pwmchipN/pwmX directory is created for
+                each exported PWM channel where X is the exported PWM
+                channel number.
+
+What:           /sys/class/pwm/pwmchipN/pwmX/period
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                Sets the PWM signal period in nanoseconds.
+
+What:           /sys/class/pwm/pwmchipN/pwmX/duty_cycle
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                Sets the PWM signal duty cycle in nanoseconds.
+
+What:           /sys/class/pwm/pwmchipN/pwmX/polarity
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                Sets the output polarity of the PWM signal to "normal" or
+                "inversed".
+
+What:           /sys/class/pwm/pwmchipN/pwmX/enable
+Date:           May 2013
+KernelVersion:  3.11
+Contact:        H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+                Enable/disable the PWM signal.
+                0 is disabled
+                1 is enabled
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 7d2b4c9b544b..1039b68fe9c6 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -45,6 +45,43 @@ 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
+-----------------------------------
+
+If CONFIG_SYSFS is enabled in your kernel configuration a simple sysfs
+interface is provided to use the PWMs from userspace. It is exposed at
+/sys/class/pwm/. Each probed PWM controller/chip will be exported as
+pwmchipN, where N is the base of the PWM chip. Inside the directory you
+will find:
+
+npwm - The number of PWM channels this chip supports (read-only).
+
+export - Exports a PWM channel for use with sysfs (write-only).
+
+unexport - Unexports a PWM channel from sysfs (write-only).
+
+The PWM channels are numbered using a per-chip index from 0 to npwm-1.
+
+When a PWM channel is exported a pwmX directory will be created in the
+pwmchipN directory it is associated with, where X is the number of the
+channel that was exported. The following properties will then be available:
+
+period - The total period of the PWM signal (read/write).
+        Value is in nanoseconds and is the sum of the active and inactive
+        time of the PWM.
+
+duty_cycle - The active time of the PWM signal (read/write).
+        Value is in nanoseconds and must be less than the period.
+
+polarity - Changes the polarity of the PWM signal (read/write).
+        Writes to this property only work if the PWM chip supports changing
+        the polarity. The polarity can only be changed if the PWM is not
+        enabled. Value is the string "normal" or "inversed".
+
+enable - Enable/disable the PWM signal (read/write).
+        0 - disabled
+        1 - enabled
+
 Implementing a PWM driver
 -------------------------
 
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index d3fe3205d296..406a4d94ddb9 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -28,6 +28,10 @@ menuconfig PWM
 
 if PWM
 
+config PWM_SYSFS
+        bool
+        default y if SYSFS
+
 config PWM_AB8500
         tristate "AB8500 PWM support"
         depends on AB8500_CORE && ARCH_U8500
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index b3afc0a1800b..859692224044 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -1,4 +1,5 @@
 obj-$(CONFIG_PWM)               += core.o
+obj-$(CONFIG_PWM_SYSFS)         += 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 0cf0f65eb037..dfbfbc521768 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_cycle = 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/sysfs.c b/drivers/pwm/sysfs.c
new file mode 100644
index 000000000000..8ca5de316d3b
--- /dev/null
+++ b/drivers/pwm/sysfs.c
@@ -0,0 +1,352 @@
+/*
+ * 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 child;
+        struct pwm_device *pwm;
+};
+
+static struct pwm_export *child_to_pwm_export(struct device *child)
+{
+        return container_of(child, struct pwm_export, child);
+}
+
+static struct pwm_device *child_to_pwm_device(struct device *child)
+{
+        struct pwm_export *export = child_to_pwm_export(child);
+
+        return export->pwm;
+}
+
+static ssize_t pwm_period_show(struct device *child,
+                               struct device_attribute *attr,
+                               char *buf)
+{
+        const struct pwm_device *pwm = child_to_pwm_device(child);
+
+        return sprintf(buf, "%u\n", pwm->period);
+}
+
+static ssize_t pwm_period_store(struct device *child,
+                                struct device_attribute *attr,
+                                const char *buf, size_t size)
+{
+        struct pwm_device *pwm = child_to_pwm_device(child);
+        unsigned int val;
+        int ret;
+
+        ret = kstrtouint(buf, 0, &val);
+        if (ret)
+                return ret;
+
+        ret = pwm_config(pwm, pwm->duty_cycle, val);
+
+        return ret ? : size;
+}
+
+static ssize_t pwm_duty_cycle_show(struct device *child,
+                                   struct device_attribute *attr,
+                                   char *buf)
+{
+        const struct pwm_device *pwm = child_to_pwm_device(child);
+
+        return sprintf(buf, "%u\n", pwm->duty_cycle);
+}
+
+static ssize_t pwm_duty_cycle_store(struct device *child,
+                                    struct device_attribute *attr,
+                                    const char *buf, size_t size)
+{
+        struct pwm_device *pwm = child_to_pwm_device(child);
+        unsigned int val;
+        int ret;
+
+        ret = kstrtouint(buf, 0, &val);
+        if (ret)
+                return ret;
+
+        ret = pwm_config(pwm, val, pwm->period);
+
+        return ret ? : size;
+}
+
+static ssize_t pwm_enable_show(struct device *child,
+                               struct device_attribute *attr,
+                               char *buf)
+{
+        const struct pwm_device *pwm = child_to_pwm_device(child);
+        int enabled = test_bit(PWMF_ENABLED, &pwm->flags);
+
+        return sprintf(buf, "%d\n", enabled);
+}
+
+static ssize_t pwm_enable_store(struct device *child,
+                                struct device_attribute *attr,
+                                const char *buf, size_t size)
+{
+        struct pwm_device *pwm = child_to_pwm_device(child);
+        int val, ret;
+
+        ret = kstrtoint(buf, 0, &val);
+        if (ret)
+                return ret;
+
+        switch (val) {
+        case 0:
+                pwm_disable(pwm);
+                break;
+        case 1:
+                ret = pwm_enable(pwm);
+                break;
+        default:
+                ret = -EINVAL;
+                break;
+        }
+
+        return ret ? : size;
+}
+
+static ssize_t pwm_polarity_show(struct device *child,
+                                 struct device_attribute *attr,
+                                 char *buf)
+{
+        const struct pwm_device *pwm = child_to_pwm_device(child);
+
+        return sprintf(buf, "%s\n", pwm->polarity ? "inversed" : "normal");
+}
+
+static ssize_t pwm_polarity_store(struct device *child,
+                                  struct device_attribute *attr,
+                                  const char *buf, size_t size)
+{
+        struct pwm_device *pwm = child_to_pwm_device(child);
+        enum pwm_polarity polarity;
+        int ret;
+
+        if (sysfs_streq(buf, "normal"))
+                polarity = PWM_POLARITY_NORMAL;
+        else if (sysfs_streq(buf, "inversed"))
+                polarity = PWM_POLARITY_INVERSED;
+        else
+                return -EINVAL;
+
+        ret = pwm_set_polarity(pwm, polarity);
+
+        return ret ? : size;
+}
+
+static DEVICE_ATTR(period, 0644, pwm_period_show, pwm_period_store);
+static DEVICE_ATTR(duty_cycle, 0644, pwm_duty_cycle_show, pwm_duty_cycle_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.attr,
+        &dev_attr_duty_cycle.attr,
+        &dev_attr_enable.attr,
+        &dev_attr_polarity.attr,
+        NULL
+};
+
+static const struct attribute_group pwm_attr_group = {
+        .attrs          = pwm_attrs,
+};
+
+static const struct attribute_group *pwm_attr_groups[] = {
+        &pwm_attr_group,
+        NULL,
+};
+
+static void pwm_export_release(struct device *child)
+{
+        struct pwm_export *export = child_to_pwm_export(child);
+
+        kfree(export);
+}
+
+static int pwm_export_child(struct device *parent, struct pwm_device *pwm)
+{
+        struct pwm_export *export;
+        int ret;
+
+        if (test_and_set_bit(PWMF_EXPORTED, &pwm->flags))
+                return -EBUSY;
+
+        export = kzalloc(sizeof(*export), GFP_KERNEL);
+        if (!export) {
+                clear_bit(PWMF_EXPORTED, &pwm->flags);
+                return -ENOMEM;
+        }
+
+        export->pwm = pwm;
+
+        export->child.release = pwm_export_release;
+        export->child.parent = parent;
+        export->child.devt = MKDEV(0, 0);
+        export->child.groups = pwm_attr_groups;
+        dev_set_name(&export->child, "pwm%u", pwm->hwpwm);
+
+        ret = device_register(&export->child);
+        if (ret) {
+                clear_bit(PWMF_EXPORTED, &pwm->flags);
+                kfree(export);
+                return ret;
+        }
+
+        return 0;
+}
+
+static int pwm_unexport_match(struct device *child, void *data)
+{
+        return child_to_pwm_device(child) == data;
+}
+
+static int pwm_unexport_child(struct device *parent, struct pwm_device *pwm)
+{
+        struct device *child;
+
+        if (!test_and_clear_bit(PWMF_EXPORTED, &pwm->flags))
+                return -ENODEV;
+
+        child = device_find_child(parent, pwm, pwm_unexport_match);
+        if (!child)
+                return -ENODEV;
+
+        /* for device_find_child() */
+        put_device(child);
+        device_unregister(child);
+        pwm_put(pwm);
+
+        return 0;
+}
+
+static ssize_t pwm_export_store(struct device *parent,
+                                struct device_attribute *attr,
+                                const char *buf, size_t len)
+{
+        struct pwm_chip *chip = dev_get_drvdata(parent);
+        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_child(parent, pwm);
+        if (ret < 0)
+                pwm_put(pwm);
+
+        return ret ? : len;
+}
+
+static ssize_t pwm_unexport_store(struct device *parent,
+                                  struct device_attribute *attr,
+                                  const char *buf, size_t len)
+{
+        struct pwm_chip *chip = dev_get_drvdata(parent);
+        unsigned int hwpwm;
+        int ret;
+
+        ret = kstrtouint(buf, 0, &hwpwm);
+        if (ret < 0)
+                return ret;
+
+        if (hwpwm >= chip->npwm)
+                return -ENODEV;
+
+        ret = pwm_unexport_child(parent, &chip->pwms[hwpwm]);
+
+        return ret ? : len;
+}
+
+static ssize_t pwm_npwm_show(struct device *parent,
+                             struct device_attribute *attr,
+                             char *buf)
+{
+        const struct pwm_chip *chip = dev_get_drvdata(parent);
+
+        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,
+};
+
+static int pwmchip_sysfs_match(struct device *parent, const void *data)
+{
+        return dev_get_drvdata(parent) == data;
+}
+
+void pwmchip_sysfs_export(struct pwm_chip *chip)
+{
+        struct device *parent;
+
+        /*
+         * If device_create() fails the pwm_chip is still usable by
+         * the kernel its just not exported.
+         */
+        parent = device_create(&pwm_class, chip->dev, MKDEV(0, 0), chip,
+                               "pwmchip%d", chip->base);
+        if (IS_ERR(parent)) {
+                dev_warn(chip->dev,
+                         "device_create failed for pwm_chip sysfs export\n");
+        }
+}
+
+void pwmchip_sysfs_unexport(struct pwm_chip *chip)
+{
+        struct device *parent;
+
+        parent = class_find_device(&pwm_class, NULL, chip,
+                                   pwmchip_sysfs_match);
+        if (parent) {
+                /* for class_find_device() */
+                put_device(parent);
+                device_unregister(parent);
+        }
+}
+
+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 a4df2042b79c..f0feafd184a0 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 +87,9 @@ struct pwm_device {
         struct pwm_chip         *chip;
         void                    *chip_data;
 
-        unsigned int            period; /* in nanoseconds */
+        unsigned int            period;         /* in nanoseconds */
+        unsigned int            duty_cycle;     /* in nanoseconds */
+        enum pwm_polarity       polarity;
 };
 
 static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
@@ -100,6 +103,17 @@ 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_cycle = duty;
+}
+
+static inline unsigned int pwm_get_duty_cycle(struct pwm_device *pwm)
+{
+        return pwm ? pwm->duty_cycle : 0;
+}
+
 /*
  * pwm_set_polarity - configure the polarity of a PWM signal
  */
@@ -278,4 +292,17 @@ 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 */