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Subject[PWM v8 1/3] PWM: Implement a generic PWM framework
Date
Updates the existing PWM-related functions to support multiple
and/or hotplugged PWM devices, and adds a sysfs interface.
Moves the code to drivers/pwm.

For now, this new code can exist alongside the current PWM
implementations; the existing implementations will be migrated
to this new framework as time permits. Eventually, the current
PWM implementation will be deprecated and then expunged.

Signed-off-by: Bill Gatliff <bgat@billgatliff.com>
---
Documentation/pwm.txt | 276 ++++++++++++++++++++++
MAINTAINERS | 8 +
drivers/Kconfig | 2 +
drivers/Makefile | 2 +
drivers/pwm/Kconfig | 10 +
drivers/pwm/Makefile | 4 +
drivers/pwm/pwm.c | 594 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/pwm/pwm.h | 140 +++++++++++
8 files changed, 1036 insertions(+), 0 deletions(-)
create mode 100644 Documentation/pwm.txt
create mode 100644 drivers/pwm/Kconfig
create mode 100644 drivers/pwm/Makefile
create mode 100644 drivers/pwm/pwm.c
create mode 100644 include/linux/pwm/pwm.h

diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
new file mode 100644
index 0000000..6a0c95d
--- /dev/null
+++ b/Documentation/pwm.txt
@@ -0,0 +1,276 @@
+ Generic PWM Device API
+
+ February 7, 2011
+ Bill Gatliff
+ <bgat@billgatliff.com>
+
+
+
+The code in drivers/pwm and include/linux/pwm/ implements an API for
+applications involving pulse-width-modulation signals. This document
+describes how the API implementation facilitates both PWM-generating
+devices, and users of those devices.
+
+
+Motivation
+
+The primary goals for implementing the "generic PWM API" are to
+consolidate the various PWM implementations within a consistent and
+redundancy-reducing framework, and to facilitate the use of
+hotpluggable PWM devices.
+
+Previous PWM-related implementations within the Linux kernel achieved
+their consistency via cut-and-paste, but did not need to (and didn't)
+facilitate more than one PWM-generating device within the system---
+hotplug or otherwise. The Generic PWM Device API might be most
+appropriately viewed as an update to those implementations, rather
+than a complete rewrite.
+
+
+Challenges
+
+One of the difficulties in implementing a generic PWM framework is the
+fact that pulse-width-modulation applications involve real-world
+signals, which often must be carefully managed to prevent destruction
+of hardware that is linked to those signals. A DC motor that
+experiences a brief interruption in the PWM signal controlling it
+might destructively overheat; it could suddenly change speed, losing
+synchronization with a sensor; it could even suddenly change direction
+or torque, breaking the mechanical device connected to it.
+
+(A generic PWM device framework is not directly responsible for
+preventing the above scenarios: that responsibility lies with the
+hardware designer, and the application and driver authors. But it
+must to the greatest extent possible make it easy to avoid such
+problems).
+
+A generic PWM device framework must accommodate the substantial
+differences between available PWM-generating hardware devices, without
+becoming sub-optimal for any of them.
+
+Finally, a generic PWM device framework must be relatively
+lightweight, computationally speaking. Some PWM users demand
+high-speed outputs, plus the ability to regulate those outputs
+quickly. A device framework must be able to "keep up" with such
+hardware, while still leaving time to do real work.
+
+The Generic PWM Device API is an attempt to meet all of the above
+requirements. At its initial publication, the API was already in use
+managing small DC motors, sensors and solenoids through a
+custom-designed, optically-isolated H-bridge driver.
+
+
+Functional Overview
+
+The Generic PWM Device API framework is implemented in
+include/linux/pwm/pwm.h and drivers/pwm/pwm.c. The functions therein
+use information from pwm_device and pwm_config structures to invoke
+services in PWM peripheral device drivers. Consult
+drivers/pwm/atmel-pwmc.c for an example driver for the Atmel PWMC
+peripheral.
+
+There are two classes of adopters of the PWM framework:
+
+ Users -- those wishing to employ the API merely to produce PWM
+ signals; once they have identified the appropriate physical output
+ on the platform in question, they don't care about the details of
+ the underlying hardware
+
+ Driver authors -- those wishing to bind devices that can generate
+ PWM signals to the Generic PWM Device API, so that the services of
+ those devices become available to users. Assuming the hardware can
+ support the needs of a user, driver authors don't care about the
+ details of the user's application
+
+Generally speaking, users will first invoke pwm_request() to obtain a
+handle to a PWM device. They will then pass that handle to functions
+like pwm_duty_ns() and pwm_period_ns() to set the duty cycle and
+period of the PWM signal, respectively. They will also invoke
+pwm_start() and pwm_stop() to turn the signal on and off.
+
+The Generic PWM API framework also provides a sysfs interface to PWM
+devices, which is adequate for basic application needs and testing.
+
+Driver authors fill out a pwm_device_ops structure, which describes
+the capabilities of the PWM hardware being utilized. They then invoke
+pwm_register() (usually from within their device's probe() handler) to
+make the PWM API aware of their device. The framework will call back
+to the methods described in the pwm_device_ops structure as users
+begin to configure and utilize the hardware.
+
+Many PWM-capable peripherals provide two, three, or more channels of
+PWM output. The driver author calls pwm_register() once for each
+channel they wish to be supported by the Generic PWM API.
+
+Note that PWM signals can be produced by a variety of peripherals,
+beyond the true PWM peripherals offered by many system-on-chip
+devices. Other possibilities include timer/counters with
+compare-match capabilities, carefully-programmed synchronous serial
+ports (e.g. SPI), and GPIO pins driven by kernel interval timers.
+With a proper pwm_device structure, these devices and pseudo-devices
+can be accommodated by the Generic PWM Device API framework.
+
+The following paragraphs describe the basic functions provided by the
+Generic PWM API framework. See the kerneldoc in drivers/pwm/pwm.c for
+the most detailed documentation.
+
+
+Using the API to Generate PWM Signals -- Basic Kernel Functions
+
+pwm_request() -- Returns a pwm_device pointer, which is subsequently
+passed to the other user-related PWM functions. Once requested, a PWM
+channel is marked as in-use and subsequent requests prior to
+pwm_release() will fail.
+
+The names used to refer to PWM devices are defined by driver authors.
+Typically they are platform device bus identifiers, and this
+convention is encouraged for consistency.
+
+pwm_release() -- Marks a PWM channel as no longer in use. The PWM
+device is stopped before it is released by the API.
+
+pwm_period_ns() -- Specifies the PWM signal's period, in nanoseconds.
+
+pwm_duty_ns() -- Specifies the PWM signal's active duration, in nanoseconds.
+
+pwm_duty_percent() -- Specifies the PWM signal's active duration, as a
+percentage of the current period of the signal. NOTE: this value is
+not recalculated if the period of the signal is subsequently changed.
+
+pwm_start(), pwm_stop() -- Turns the PWM signal on and off. Except
+where stated otherwise by a driver author, signals are stopped at the
+end of the current period, at which time the output is set to its
+inactive state.
+
+pwm_polarity() -- Defines whether the PWM signal output's active
+region is "1" or "0". A 10% duty-cycle, polarity=1 signal will
+conventionally be at 5V (or 3.3V, or 1000V, or whatever the platform
+hardware does) for 10% of the period. The same configuration of a
+polarity=0 signal will be at 5V (or 3.3V, or ...) for 90% of the
+period.
+
+
+Using the Sysfs Interface to Generate PWM Signals from Userspace
+
+The Generic PWM API provides the following attributes under
+/sys/class/pwm/<device>/ to allow user applications to control
+and/or monitor PWM signal generation. Except for the 'export'
+attribute, all attributes are read-only if the PWM device is not
+exported to userspace.
+
+export (rw) -- write a label to this attribute to request that the PWM
+device be exported to userspace; returns the length of the label on
+success (for compatibilty with echo/cat), or -EBUSY if the device is
+already in use by the kernel or has already been exported to
+userspace. Read from this attribute to obtain the label of the current
+PWM device owner, if any.
+
+unexport (w) -- write a non-null string to this attribute to release
+the PWM device; the device then becomes available for reexport and/or
+requests. Returns -EBUSY if the device is not currently exported,
+-EINVAL if the device is not currently in use, or the length of the
+string on success.
+
+polarity (rw) -- write an ascii '1' to set active high, or a '0' for
+active low. Read to obtain the current polarity.
+
+period_ns (rw) -- write an ascii decimal number to set the period of
+the PWM device, in nanoseconds. Value written must not be less than
+duty_ns or -EINVAL is returned. Read to determine the current period
+of the PWM device, which might be slightly different than the value
+requested due to hardware limitations.
+
+duty_ns (rw) -- write an ascii decimal number to set the duration of
+the active portion of the PWM period, in nanoseconds; value written
+must not exceed period_ns. Read to obtain current duty_ns, which may
+be slightly different than the value requested due to hardware
+limitations.
+
+tick_hz (r) -- indicates the base tick rate of the underlying
+hardware, in nanoseconds. Returns '0' if the rate is not yet known,
+which might be the case if the device has not been requested yet (some
+drivers don't initialize this value until the hardware is requested,
+because the value is dynamic).
+
+run (rw) -- write '1' to start PWM signal generation, '0' to stop.
+Read to determine whether the PWM device is running or not.
+
+
+Using the API to Generate PWM Signals -- Advanced Functions
+
+pwm_config() -- Passes a pwm_config structure to the associated device
+driver. This function is invoked by pwm_start(), pwm_duty_ns(),
+etc. and is one of two main entry points to the PWM driver for the
+hardware being used. The configuration change is guaranteed atomic if
+multiple configuration changes are specified by the config structure.
+This function might sleep, depending on what the device driver has to
+do to satisfy the request. All PWM device drivers must support this
+entry point.
+
+pwm_config_nosleep() -- Passes a pwm_config structure to the
+associated device driver. If the driver must sleep in order to
+implement the requested configuration change, -EWOULDBLOCK is
+returned. Users may call this function from interrupt handlers, timer
+handlers, and other interrupt contexts, but must confine their
+configuration changes to only those that the driver can implement
+without sleeping. This is the other main entry point into the PWM
+hardware driver, but not all device drivers support this entry point.
+
+pwm_synchronize(), pwm_unsynchronize() -- "Synchronizes" two or more
+PWM channels, if the underlying hardware permits. (If it doesn't, the
+framework facilitates emulating this capability but it is not yet
+implemented). Synchronized channels will start and stop
+simultaneously when any single channel in the group is started or
+stopped. Use pwm_unsynchronize(..., NULL) to completely detach a
+channel from any other synchronized channels. By default, all PWM
+channels are unsynchronized.
+
+
+Implementing a PWM Device API Driver -- Functions for Driver Authors
+
+
+request -- (optional) Invoked each time a user requests a channel.
+Use to turn on clocks, clean up register states, etc. The framework
+takes care of device locking/unlocking; you will see only successful
+requests.
+
+release -- (optional) Invoked each time a user relinquishes a channel.
+The framework will have already stopped, unsynchronized and un-handled
+the channel. Use to turn off clocks, etc. as necessary.
+
+config -- Invoked to change the device configuration, always from a
+sleep-compatible context. All the changes indicated must be performed
+atomically, ideally synchronized to an end-of-period event (so that
+you avoid short or long output pulses). You may sleep, etc. as
+necessary within this function.
+
+config_nosleep -- (optional) Invoked to change device configuration
+from within a context that is not allowed to sleep. If you cannot
+perform the requested configuration changes without sleeping, return
+-EWOULDBLOCK.
+
+
+FAQs and Additional Notes
+
+The Atmel PWMC pwm_config() function tries to satisfy the user's
+configuration request by first invoking pwm_config_nosleep(). If that
+operation fails, then the PWM peripheral is brought to a synchronized
+stop, the configuration changes are made, and the device is restarted.
+
+The Atmel PWMC's use of pwm_config_nosleep() from pwm_config()
+minimizes redundant code between the two functions, and relieves the
+pwm_config() function of the need to explicitly test whether a
+requested configuration change can be carried out while the PWM device
+is in its current mode.
+
+PWM API driver authors are encouraged to adopt the Atmel PWMC's
+pwm_config()-vs.-pwm_config_nosleep() strategy in implementations for
+other devices as well.
+
+
+Acknowledgements
+
+The author expresses his gratitude to the countless developers who
+have reviewed and submitted feedback on the various versions of the
+Generic PWM Device API code, and those who have submitted drivers and
+applications that use the framework. You know who you are. ;)
diff --git a/MAINTAINERS b/MAINTAINERS
index 560ecce..c9f7f3a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5041,6 +5041,14 @@ S: Maintained
F: Documentation/video4linux/README.pvrusb2
F: drivers/media/video/pvrusb2/

+PWM DEVICE API
+M: Bill Gatliff <bgat@billgatliff.com>
+L: linux-embedded@vger.kernel.org
+T: git git://git.billgatliff.com/pwm.git
+S: Maintained
+F: Documentation/pwm.txt
+F: drivers/pwm/
+
PXA2xx/PXA3xx SUPPORT
M: Eric Miao <eric.y.miao@gmail.com>
M: Russell King <linux@arm.linux.org.uk>
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 9bfb71f..413e4f9 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -56,6 +56,8 @@ source "drivers/pps/Kconfig"

source "drivers/gpio/Kconfig"

+source "drivers/pwm/Kconfig"
+
source "drivers/w1/Kconfig"

source "drivers/power/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index b423bb1..4e37abf 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -6,6 +6,8 @@
#

obj-y += gpio/
+obj-$(CONFIG_GENERIC_PWM) += pwm/
+
obj-$(CONFIG_PCI) += pci/
obj-$(CONFIG_PARISC) += parisc/
obj-$(CONFIG_RAPIDIO) += rapidio/
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
new file mode 100644
index 0000000..bc550f7
--- /dev/null
+++ b/drivers/pwm/Kconfig
@@ -0,0 +1,10 @@
+#
+# PWM infrastructure and devices
+#
+
+menuconfig GENERIC_PWM
+ tristate "PWM Support"
+ help
+ Enables PWM device support implemented via a generic
+ framework. If unsure, say N.
+
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
new file mode 100644
index 0000000..7baa201
--- /dev/null
+++ b/drivers/pwm/Makefile
@@ -0,0 +1,4 @@
+#
+# Makefile for pwm devices
+#
+obj-$(CONFIG_GENERIC_PWM) := pwm.o
diff --git a/drivers/pwm/pwm.c b/drivers/pwm/pwm.c
new file mode 100644
index 0000000..18c511b
--- /dev/null
+++ b/drivers/pwm/pwm.c
@@ -0,0 +1,594 @@
+/*
+ * PWM API implementation
+ *
+ * Copyright (C) 2011 Bill Gatliff <bgat@billgatliff.com>
+ * Copyright (C) 2011 Arun Murthy <arun.murthy@stericsson.com>
+ *
+ * This program is free software; you may redistribute and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/completion.h>
+#include <linux/workqueue.h>
+#include <linux/list.h>
+#include <linux/sched.h>
+#include <linux/pwm/pwm.h>
+
+static const char *REQUEST_SYSFS = "sysfs";
+static DEFINE_MUTEX(device_list_mutex);
+static struct class pwm_class;
+
+void pwm_set_drvdata(struct pwm_device *p, void *data)
+{
+ dev_set_drvdata(&p->dev, data);
+}
+EXPORT_SYMBOL(pwm_set_drvdata);
+
+void *pwm_get_drvdata(const struct pwm_device *p)
+{
+ return dev_get_drvdata(&p->dev);
+}
+EXPORT_SYMBOL(pwm_get_drvdata);
+
+static inline struct pwm_device *to_pwm_device(struct device *dev)
+{
+ return container_of(dev, struct pwm_device, dev);
+}
+
+static int pwm_match_name(struct device *dev, void *name)
+{
+ return !strcmp(name, dev_name(dev));
+}
+
+static int __pwm_request(struct pwm_device *p, const char *label)
+{
+ int ret;
+
+ if (!try_module_get(p->ops->owner))
+ return -ENODEV;
+
+ ret = test_and_set_bit(PWM_FLAG_REQUESTED, &p->flags);
+ if (ret) {
+ ret = -EBUSY;
+ goto err_flag_requested;
+ }
+
+ p->label = label;
+
+ if (p->ops->request) {
+ ret = p->ops->request(p);
+ if (ret)
+ goto err_request_ops;
+
+ }
+
+ return 0;
+
+err_request_ops:
+ clear_bit(PWM_FLAG_REQUESTED, &p->flags);
+
+err_flag_requested:
+ module_put(p->ops->owner);
+ return ret;
+}
+
+static struct pwm_device *__pwm_request_byname(const char *name,
+ const char *label)
+{
+ struct device *d;
+ struct pwm_device *p;
+ int ret;
+
+ d = class_find_device(&pwm_class, NULL, (char*)name, pwm_match_name);
+ if (IS_ERR_OR_NULL(d))
+ return ERR_PTR(-EINVAL);
+
+ p = to_pwm_device(d);
+ ret = __pwm_request(p, label);
+
+ if (ret)
+ return ERR_PTR(ret);
+ return p;
+}
+
+/**
+ * pwm_request - request a PWM device by name
+ *
+ * @name: name of PWM device
+ * @label: label that identifies requestor
+ *
+ * The @name format is driver-specific, but is typically of the form
+ * "<bus_id>:<chan>". For example, "atmel_pwmc:1" identifies the
+ * second ATMEL PWMC peripheral channel.
+ *
+ * Returns a pointer to the requested PWM device on success, -EINVAL
+ * otherwise.
+ */
+struct pwm_device *pwm_request(const char *name, const char *label)
+{
+ struct pwm_device *p;
+
+ mutex_lock(&device_list_mutex);
+ p = __pwm_request_byname(name, label);
+ mutex_unlock(&device_list_mutex);
+ return p;
+}
+EXPORT_SYMBOL(pwm_request);
+
+/**
+ * pwm_release - releases a previously-requested PWM channel
+ *
+ * @p: PWM device to release
+ */
+void pwm_release(struct pwm_device *p)
+{
+ mutex_lock(&device_list_mutex);
+
+ if (!test_and_clear_bit(PWM_FLAG_REQUESTED, &p->flags)) {
+ WARN(1, "%s: releasing unrequested PWM device %s\n",
+ __func__, dev_name(&p->dev));
+ goto done;
+ }
+
+ pwm_stop(p);
+ pwm_unsynchronize(p, NULL);
+ p->label = NULL;
+
+ if (p->ops->release)
+ p->ops->release(p);
+
+ put_device(&p->dev);
+ module_put(p->ops->owner);
+
+done:
+ mutex_unlock(&device_list_mutex);
+}
+EXPORT_SYMBOL(pwm_release);
+
+static unsigned long pwm_ns_to_ticks(struct pwm_device *p, unsigned long nsecs)
+{
+ unsigned long long ticks;
+
+ ticks = nsecs;
+ ticks *= p->tick_hz;
+ do_div(ticks, 1000000000);
+ return ticks;
+}
+
+static unsigned long pwm_ticks_to_ns(struct pwm_device *p, unsigned long ticks)
+{
+ unsigned long long ns;
+
+ if (!p->tick_hz)
+ return 0;
+
+ ns = ticks;
+ ns *= 1000000000UL;
+ do_div(ns, p->tick_hz);
+ return ns;
+}
+
+/**
+ * pwm_config_nosleep - configures a PWM device in an atomic context
+ *
+ * @p: PWM device to configure
+ * @c: configuration to apply to the PWM device
+ *
+ * Returns whatever the PWM device driver's config_nosleep() returns,
+ * or -ENOSYS if the PWM device driver does not have a
+ * config_nosleep() method.
+ */
+int pwm_config_nosleep(struct pwm_device *p, struct pwm_config *c)
+{
+ if (!p->ops->config_nosleep)
+ return -ENOSYS;
+
+ return p->ops->config_nosleep(p, c);
+}
+EXPORT_SYMBOL(pwm_config_nosleep);
+
+/**
+ * pwm_config - configures a PWM device
+ *
+ * @p: PWM device to configure
+ * @c: configuration to apply to the PWM device
+ *
+ * Performs some basic sanity checking of the parameters, and returns
+ * -EINVAL if they are found to be invalid. Otherwise, returns
+ * whatever the PWM device's config() method returns.
+ */
+int pwm_config(struct pwm_device *p, struct pwm_config *c)
+{
+ int ret = 0;
+
+ dev_dbg(&p->dev, "%s: config_mask %lu period_ticks %lu "
+ "duty_ticks %lu polarity %d\n",
+ __func__, c->config_mask, c->period_ticks,
+ c->duty_ticks, c->polarity);
+
+ switch (c->config_mask & (BIT(PWM_CONFIG_PERIOD_TICKS)
+ | BIT(PWM_CONFIG_DUTY_TICKS))) {
+ case BIT(PWM_CONFIG_PERIOD_TICKS):
+ if (p->duty_ticks > c->period_ticks)
+ ret = -EINVAL;
+ break;
+ case BIT(PWM_CONFIG_DUTY_TICKS):
+ if (p->period_ticks < c->duty_ticks)
+ ret = -EINVAL;
+ break;
+ case BIT(PWM_CONFIG_DUTY_TICKS) | BIT(PWM_CONFIG_PERIOD_TICKS):
+ if (c->duty_ticks > c->period_ticks)
+ ret = -EINVAL;
+ break;
+ default:
+ break;
+ }
+
+ if (ret)
+ return ret;
+ return p->ops->config(p, c);
+}
+EXPORT_SYMBOL(pwm_config);
+
+/**
+ * pwm_set - compatibility function to ease migration from older code
+ * @p: the PWM device to configure
+ * @period_ns: period of the desired PWM signal, in nanoseconds
+ * @duty_ns: duration of active portion of desired PWM signal, in nanoseconds
+ * @polarity: 1 if active period is high, zero otherwise
+ */
+int pwm_set(struct pwm_device *p, unsigned long period_ns,
+ unsigned long duty_ns, int polarity)
+{
+ struct pwm_config c = {
+ .config_mask = (BIT(PWM_CONFIG_PERIOD_TICKS)
+ | BIT(PWM_CONFIG_DUTY_TICKS)
+ | BIT(PWM_CONFIG_POLARITY)),
+ .period_ticks = pwm_ns_to_ticks(p, period_ns),
+ .duty_ticks = pwm_ns_to_ticks(p, duty_ns),
+ .polarity = polarity
+ };
+
+ return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_set);
+
+int pwm_set_period_ns(struct pwm_device *p, unsigned long period_ns)
+{
+ struct pwm_config c = {
+ .config_mask = BIT(PWM_CONFIG_PERIOD_TICKS),
+ .period_ticks = pwm_ns_to_ticks(p, period_ns),
+ };
+
+ return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_set_period_ns);
+
+unsigned long pwm_get_period_ns(struct pwm_device *p)
+{
+ return pwm_ticks_to_ns(p, p->period_ticks);
+}
+EXPORT_SYMBOL(pwm_get_period_ns);
+
+int pwm_set_duty_ns(struct pwm_device *p, unsigned long duty_ns)
+{
+ struct pwm_config c = {
+ .config_mask = BIT(PWM_CONFIG_DUTY_TICKS),
+ .duty_ticks = pwm_ns_to_ticks(p, duty_ns),
+ };
+ return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_set_duty_ns);
+
+unsigned long pwm_get_duty_ns(struct pwm_device *p)
+{
+ return pwm_ticks_to_ns(p, p->duty_ticks);
+}
+EXPORT_SYMBOL(pwm_get_duty_ns);
+
+int pwm_set_polarity(struct pwm_device *p, int polarity)
+{
+ struct pwm_config c = {
+ .config_mask = BIT(PWM_CONFIG_POLARITY),
+ .polarity = polarity,
+ };
+ return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_set_polarity);
+
+int pwm_start(struct pwm_device *p)
+{
+ struct pwm_config c = {
+ .config_mask = BIT(PWM_CONFIG_START),
+ };
+ return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_start);
+
+int pwm_stop(struct pwm_device *p)
+{
+ struct pwm_config c = {
+ .config_mask = BIT(PWM_CONFIG_STOP),
+ };
+ return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_stop);
+
+int pwm_synchronize(struct pwm_device *p, struct pwm_device *to_p)
+{
+ if (!p->ops->synchronize)
+ return -ENOSYS;
+
+ return p->ops->synchronize(p, to_p);
+}
+EXPORT_SYMBOL(pwm_synchronize);
+
+int pwm_unsynchronize(struct pwm_device *p, struct pwm_device *from_p)
+{
+ if (!p->ops->unsynchronize)
+ return -ENOSYS;
+
+ return p->ops->unsynchronize(p, from_p);
+}
+EXPORT_SYMBOL(pwm_unsynchronize);
+
+static ssize_t pwm_run_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+ return sprintf(buf, "%d\n", pwm_is_running(p));
+}
+
+static ssize_t pwm_run_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+ int ret;
+
+ if (!pwm_is_exported(p))
+ return -EPERM;
+
+ if (sysfs_streq(buf, "1"))
+ pwm_start(p);
+ else if (sysfs_streq(buf, "0"))
+ pwm_stop(p);
+ else
+ return -EINVAL;
+
+ return len;
+}
+
+static ssize_t pwm_tick_hz_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+ return sprintf(buf, "%lu\n", p->tick_hz);
+}
+
+static ssize_t pwm_duty_ns_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+ return sprintf(buf, "%lu\n", pwm_get_duty_ns(p));
+}
+
+static ssize_t pwm_duty_ns_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ unsigned long duty_ns;
+ struct pwm_device *p = to_pwm_device(dev);
+ int ret;
+
+ if (!pwm_is_exported(p))
+ return -EPERM;
+
+ ret = strict_strtoul(buf, 10, &duty_ns);
+ if (ret)
+ return ret;
+ pwm_set_duty_ns(p, duty_ns);
+ return len;
+}
+
+static ssize_t pwm_period_ns_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+ return sprintf(buf, "%lu\n", pwm_get_period_ns(p));
+}
+
+static ssize_t pwm_period_ns_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ unsigned long period_ns;
+ struct pwm_device *p = to_pwm_device(dev);
+
+ if (!pwm_is_exported(p))
+ return -EPERM;
+
+ if (!strict_strtoul(buf, 10, &period_ns))
+ pwm_set_period_ns(p, period_ns);
+ return len;
+}
+
+static ssize_t pwm_polarity_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+ return sprintf(buf, "%d\n", p->polarity ? 1 : 0);
+}
+
+static ssize_t pwm_polarity_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ unsigned long polarity;
+ struct pwm_device *p = to_pwm_device(dev);
+
+ if (!pwm_is_exported(p))
+ return -EPERM;
+
+ if (!strict_strtoul(buf, 10, &polarity))
+ pwm_set_polarity(p, polarity);
+ return len;
+}
+
+static ssize_t pwm_export_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+
+ if (pwm_is_exported(p))
+ return sprintf(buf, "%s\n", p->label);
+ else if (pwm_is_requested(p))
+ return -EBUSY;
+ return 0;
+}
+
+static ssize_t pwm_export_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+ int ret;
+
+ mutex_lock(&device_list_mutex);
+ if (pwm_is_exported(p))
+ ret = -EBUSY;
+ else
+ ret = __pwm_request(p, REQUEST_SYSFS);
+
+ if (!ret)
+ set_bit(PWM_FLAG_EXPORTED, &p->flags);
+ mutex_unlock(&device_list_mutex);
+
+ return ret ? ret : len;
+}
+
+static ssize_t pwm_unexport_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct pwm_device *p = to_pwm_device(dev);
+
+ if (!pwm_is_exported(p) || !pwm_is_requested(p))
+ return -EINVAL;
+
+ pwm_release(p);
+ clear_bit(PWM_FLAG_EXPORTED, &p->flags);
+ return len;
+}
+
+static struct device_attribute pwm_dev_attrs[] = {
+ __ATTR(export, S_IRUGO | S_IWUSR, pwm_export_show, pwm_export_store),
+ __ATTR(unexport, S_IWUSR, NULL, pwm_unexport_store),
+ __ATTR(polarity, S_IRUGO | S_IWUSR, pwm_polarity_show, pwm_polarity_store),
+ __ATTR(period_ns, S_IRUGO | S_IWUSR, pwm_period_ns_show, pwm_period_ns_store),
+ __ATTR(duty_ns, S_IRUGO | S_IWUSR, pwm_duty_ns_show, pwm_duty_ns_store),
+ __ATTR(tick_hz, S_IRUGO, pwm_tick_hz_show, NULL),
+ __ATTR(run, S_IRUGO | S_IWUSR, pwm_run_show, pwm_run_store),
+ __ATTR_NULL,
+};
+
+static struct class pwm_class = {
+ .name = "pwm",
+ .owner = THIS_MODULE,
+ .dev_attrs = pwm_dev_attrs,
+};
+
+static void __pwm_release(struct device *dev)
+{
+ struct pwm_device *p = container_of(dev, struct pwm_device, dev);
+ kfree(p);
+}
+
+/**
+ * pwm_register - registers a PWM device
+ *
+ * @ops: PWM device operations
+ * @parent: reference to parent device, if any
+ * @fmt: printf-style format specifier for device name
+ */
+struct pwm_device *pwm_register(const struct pwm_device_ops *ops,
+ struct device *parent, const char *fmt, ...)
+{
+ struct pwm_device *p;
+ int ret;
+ va_list vargs;
+
+ if (!ops || !ops->config)
+ return ERR_PTR(-EINVAL);
+
+ p = kzalloc(sizeof(*p), GFP_KERNEL);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ p->ops = ops;
+
+ p->dev.devt = MKDEV(0, 0);
+ p->dev.class = &pwm_class;
+ p->dev.parent = parent;
+ p->dev.release = __pwm_release;
+
+ va_start(vargs, fmt);
+ ret = kobject_set_name_vargs(&p->dev.kobj, fmt, vargs);
+
+ ret = device_register(&p->dev);
+ if (ret)
+ goto err;
+
+ return p;
+
+err:
+ put_device(&p->dev);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(pwm_register);
+
+void pwm_unregister(struct pwm_device *p)
+{
+ device_unregister(&p->dev);
+}
+EXPORT_SYMBOL(pwm_unregister);
+
+static int __init pwm_init(void)
+{
+ return class_register(&pwm_class);
+}
+
+static void __exit pwm_exit(void)
+{
+ class_unregister(&pwm_class);
+}
+
+postcore_initcall(pwm_init);
+module_exit(pwm_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Bill Gatliff <bgat@billgatliff.com>");
+MODULE_DESCRIPTION("Generic PWM device API implementation");
diff --git a/include/linux/pwm/pwm.h b/include/linux/pwm/pwm.h
new file mode 100644
index 0000000..9390754
--- /dev/null
+++ b/include/linux/pwm/pwm.h
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2011 Bill Gatliff < bgat@billgatliff.com>
+ * Copyright (C) 2011 Arun Murthy <arun.murth@stericsson.com>
+ *
+ * This program is free software; you may redistribute and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA
+ */
+#ifndef __LINUX_PWM_H
+#define __LINUX_PWM_H
+
+#include <linux/device.h>
+
+enum {
+ PWM_FLAG_REQUESTED = 0,
+ PWM_FLAG_STOP = 1,
+ PWM_FLAG_RUNNING = 2,
+ PWM_FLAG_EXPORTED = 3,
+};
+
+enum {
+ PWM_CONFIG_DUTY_TICKS = 0,
+ PWM_CONFIG_PERIOD_TICKS = 1,
+ PWM_CONFIG_POLARITY = 2,
+ PWM_CONFIG_START = 3,
+ PWM_CONFIG_STOP = 4,
+};
+
+struct pwm_config;
+struct pwm_device;
+
+struct pwm_device_ops {
+ struct module *owner;
+
+ int (*request) (struct pwm_device *p);
+ void (*release) (struct pwm_device *p);
+ int (*config) (struct pwm_device *p,
+ struct pwm_config *c);
+ int (*config_nosleep) (struct pwm_device *p,
+ struct pwm_config *c);
+ int (*synchronize) (struct pwm_device *p,
+ struct pwm_device *to_p);
+ int (*unsynchronize) (struct pwm_device *p,
+ struct pwm_device *from_p);
+};
+
+/**
+ * struct pwm_config - configuration data for a PWM device
+ *
+ * @config_mask: which fields are valid
+ * @duty_ticks: requested duty cycle, in ticks
+ * @period_ticks: requested period, in ticks
+ * @polarity: active high (1), or active low (0)
+ */
+struct pwm_config {
+ unsigned long config_mask;
+ unsigned long duty_ticks;
+ unsigned long period_ticks;
+ int polarity;
+};
+
+/**
+ * struct pwm_device - represents a PWM device
+ *
+ * @dev: device model reference
+ * @ops: operations supported by the PWM device
+ * @label: requestor of the PWM device, or NULL
+ * @flags: PWM device state, see FLAG_*
+ * @tick_hz: base tick rate of PWM device, in HZ
+ * @polarity: active high (1), or active low (0)
+ * @period_ticks: PWM device's current period, in ticks
+ * @duty_ticks: duration of PWM device's active cycle, in ticks
+ */
+struct pwm_device {
+ struct device dev;
+ const struct pwm_device_ops *ops;
+ const char *label;
+ unsigned long flags;
+ unsigned long tick_hz;
+ int polarity;
+ unsigned long period_ticks;
+ unsigned long duty_ticks;
+};
+
+struct pwm_device *pwm_request(const char *name, const char *label);
+void pwm_release(struct pwm_device *p);
+
+static inline int pwm_is_requested(const struct pwm_device *p)
+{
+ return test_bit(PWM_FLAG_REQUESTED, &p->flags);
+}
+
+static inline int pwm_is_running(const struct pwm_device *p)
+{
+ return test_bit(PWM_FLAG_RUNNING, &p->flags);
+}
+
+static inline int pwm_is_exported(const struct pwm_device *p)
+{
+ return test_bit(PWM_FLAG_EXPORTED, &p->flags);
+}
+
+struct pwm_device *pwm_register(const struct pwm_device_ops *ops, struct device *parent,
+ const char *fmt, ...);
+void pwm_unregister(struct pwm_device *p);
+
+void pwm_set_drvdata(struct pwm_device *p, void *data);
+void *pwm_get_drvdata(const struct pwm_device *p);
+
+int pwm_set(struct pwm_device *p, unsigned long period_ns,
+ unsigned long duty_ns, int polarity);
+
+int pwm_set_period_ns(struct pwm_device *p, unsigned long period_ns);
+unsigned long pwm_get_period_ns(struct pwm_device *p);
+
+int pwm_set_duty_ns(struct pwm_device *p, unsigned long duty_ns);
+unsigned long pwm_get_duty_ns(struct pwm_device *p);
+
+int pwm_set_polarity(struct pwm_device *p, int polarity);
+
+int pwm_start(struct pwm_device *p);
+int pwm_stop(struct pwm_device *p);
+
+int pwm_config_nosleep(struct pwm_device *p, struct pwm_config *c);
+int pwm_config(struct pwm_device *p, struct pwm_config *c);
+
+int pwm_synchronize(struct pwm_device *p, struct pwm_device *to_p);
+int pwm_unsynchronize(struct pwm_device *p, struct pwm_device *from_p);
+
+#endif
--
1.7.2.3


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