pwm: Add sysfs interface
authorH Hartley Sweeten <hartleys@visionengravers.com>
Tue, 11 Jun 2013 17:38:59 +0000 (10:38 -0700)
committerThierry Reding <thierry.reding@gmail.com>
Fri, 21 Jun 2013 09:32:51 +0000 (11:32 +0200)
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>
Documentation/ABI/testing/sysfs-class-pwm [new file with mode: 0644]
Documentation/pwm.txt
drivers/pwm/Kconfig
drivers/pwm/Makefile
drivers/pwm/core.c
drivers/pwm/sysfs.c [new file with mode: 0644]
include/linux/pwm.h

diff --git a/Documentation/ABI/testing/sysfs-class-pwm b/Documentation/ABI/testing/sysfs-class-pwm
new file mode 100644 (file)
index 0000000..c479d77
--- /dev/null
@@ -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
index 7d2b4c9b544b3c28596bec44c05a62dfadfdc260..1039b68fe9c62aa773f4e90e68613870c0cd9db3 100644 (file)
@@ -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
 -------------------------
 
index d3fe3205d2960e5a7031053eae22f777406a1363..406a4d94ddb9111abc3cda447b90b7d1550ff9d3 100644 (file)
@@ -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
index b3afc0a1800bf740a3360a0dcfe27a6f456adb5d..85969222404429eef794200e44b3bd97a9bd835b 100644 (file)
@@ -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
index 0cf0f65eb037ad20ad750dac4c5cbf0b1ab4f73c..dfbfbc5217683de697d1c834f73c55de0ff850de 100644 (file)
@@ -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 (file)
index 0000000..8ca5de3
--- /dev/null
@@ -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);
index a4df2042b79c15f75bf53dd8d185fd6c80426b05..f0feafd184a0d655fff326bc979eebd21a7a28ab 100644 (file)
@@ -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 */