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>

1 files changed, 352 insertions, 0 deletions

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);