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 (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
Signed-off-by: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
Cc: Lars Poeschel <poeschel@xxxxxxxxxxx>
Cc: Ryan Mallon <rmallon@xxxxxxxxx>
Cc: Rob Landley <rob@xxxxxxxxxxx>
---
v4: * address a number of issues pointed out by Thierry Reding
- fix some typos and wording issues in the Documentation
- rename the new source file to sysfs.c
- rename some of the variables in sysfs.c to clarify them
- fix the period store so it does not change the duty cycle
- change the polarity attribute to use a string representation
- add a warning message is the pwmchip_sysfs_export() fails
v3: * fix an issue with the export/unexport of the PWM chip
v2: * add API documentation and update Documentation/pwm.txt
* fix some issues pointed out by Ryan Mallon
* add the pwm attributes to dev.groups so they are created
when the device is registered for the exported PWM
v1: * Based on previous work by Lars Poecshel
Documentation/ABI/testing/sysfs-class-pwm | 78 +++++++
Documentation/pwm.txt | 36 +++
drivers/pwm/Kconfig | 12 +
drivers/pwm/Makefile | 1 +
drivers/pwm/core.c | 25 ++-
drivers/pwm/sysfs.c | 351 ++++++++++++++++++++++++++++++
include/linux/pwm.h | 29 ++-
7 files changed, 529 insertions(+), 3 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-class-pwm
create mode 100644 drivers/pwm/sysfs.c
diff --git a/Documentation/ABI/testing/sysfs-class-pwm b/Documentation/ABI/testing/sysfs-class-pwm
new file mode 100644
index 0000000..cb3d034
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-pwm
@@ -0,0 +1,78 @@
+What: /sys/class/pwm/
+Date: May 2013
+KernelVersion: 3.11
+Contact: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
+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@xxxxxxxxxxxxxxxxxxx>
+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@xxxxxxxxxxxxxxxxxxx>
+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@xxxxxxxxxxxxxxxxxxx>
+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@xxxxxxxxxxxxxxxxxxx>
+Description:
+ Unexports a PWM channel.
+
+What: /sys/class/pwm/pwmchipN/pwmX
+Date: May 2013
+KernelVersion: 3.11
+Contact: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
+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@xxxxxxxxxxxxxxxxxxx>
+Description:
+ Sets the PWM period in nanoseconds.
+
+What: /sys/class/pwm/pwmchipN/pwmX/duty
+Date: May 2013
+KernelVersion: 3.11
+Contact: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
+Description:
+ Sets the PWM duty cycle in nanoseconds.
+
+What: /sys/class/pwm/pwmchipN/pwmX/polarity
+Date: May 2013
+KernelVersion: 3.11
+Contact: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
+Description:
+ Sets the output polarity of the PWM to "normal" or "inversed".
+
+What: /sys/class/pwm/pwmchipN/pwmX/enable
+Date: May 2013
+KernelVersion: 3.11
+Contact: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
+Description:
+ Enables/disables the PWM.
+ 0 is disabled
+ 1 is enabled
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 7d2b4c9..95589b1 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -45,6 +45,42 @@ 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/. 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 - The active time of the PWM (read/write).
+ Value is in nanoseconds and must be less than the period.
+
+polarity - Changes the polarity of the PWM (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 - Enables/disables the PWM (read/write).
+ 0 - disabled
+ 1 - enabled
+
Implementing a PWM driver
-------------------------
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 115b644..e77405d 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 provide a sysfs interface to control PWMs.
+
+ For every instance of a PWM device there is a pwmchipN directory
+ created in /sys/class/pwm. Use the export attribute to request
+ a PWM to be accessible from userspace and the unexport attribute
+ to return the PWM to the kernel. Each exported PWM will have a
+ pwmX directory in the pwmchipN it is associated with.
+
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..a025439 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 32221cb..9e9f5b8 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 0000000..827a526
--- /dev/null
+++ b/drivers/pwm/sysfs.c
@@ -0,0 +1,351 @@
+/*
+ * A simple sysfs interface for the generic PWM framework
+ *
+ * Copyright (C) 2013 H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
+ *
+ * Based on previous work by Lars Poeschel <poeschel@xxxxxxxxxxx>
+ *
+ * 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_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_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 (strncmp(buf, "normal", strlen("normal")) == 0) {
+ polarity = PWM_POLARITY_NORMAL;
+ } else if (strncmp(buf, "inversed", strlen("inversed")) == 0) {
+ 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, 0644, pwm_duty_show, pwm_duty_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.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;
+
+ put_device(child); /* for device_find_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) {
+ put_device(parent); /* for class_find_device() */
+ 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 a4df204..f0feafd 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 */
--
1.8.1.4
--
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