[RFC,1/6,PWM] Generic PWM API implementation

diff --git a/drivers/pwm/pwm.c b/drivers/pwm/pwm.c
new file mode 100644
index 0000000..2f28c20
--- /dev/null
+++ b/drivers/pwm/pwm.c
@@ -0,0 +1,667 @@ 
+/*
+ * drivers/pwm/pwm.c
+ *
+ * Copyright (C) 2008 Bill Gatliff
+ *
+ * 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 of the License, 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.
+ *
+ * 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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/spinlock.h>
+#include <linux/fs.h>
+#include <linux/completion.h>
+#include <linux/workqueue.h>
+#include <linux/pwm.h>
+
+
+static int __pwm_create_sysfs(struct pwm_device *pwm);
+
+static LIST_HEAD(pwm_device_list);
+static DEFINE_MUTEX(device_list_mutex);
+static struct class pwm_class;
+static struct workqueue_struct *pwm_handler_workqueue;
+
+
+int pwm_register(struct pwm_device *pwm)
+{
+	struct pwm_channel *p;
+	int wchan;
+	int ret = 0;
+
+	spin_lock_init(&pwm->list_lock);
+
+	p = kcalloc(pwm->nchan, sizeof(struct pwm_channel), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	for (wchan = 0; wchan < pwm->nchan; wchan++) {
+		spin_lock_init(&p[wchan].lock);
+		init_completion(&p[wchan].complete);
+		p[wchan].chan = wchan;
+		p[wchan].pwm = pwm;
+	}
+
+	pwm->channels = p;
+
+	mutex_lock(&device_list_mutex);
+
+	list_add_tail(&pwm->list, &pwm_device_list);
+	ret = __pwm_create_sysfs(pwm);
+	if (ret) {
+		mutex_unlock(&device_list_mutex);
+		goto err_create_sysfs;
+	}
+
+	mutex_unlock(&device_list_mutex);
+
+	pr_info("%s: %d channels\n", pwm->bus_id, pwm->nchan);
+	return 0;
+
+err_create_sysfs:
+	kfree(p);
+
+	return ret;
+}
+EXPORT_SYMBOL(pwm_register);
+
+
+static int __match_device(struct device *dev, void *data)
+{
+	return dev_get_drvdata(dev) == data;
+}
+
+
+int pwm_unregister(struct pwm_device *pwm)
+{
+	int wchan;
+	struct device *dev;
+
+	mutex_lock(&device_list_mutex);
+
+	for (wchan = 0; wchan < pwm->nchan; wchan++) {
+		if (pwm->channels[wchan].flags & FLAG_REQUESTED) {
+			mutex_unlock(&device_list_mutex);
+			return -EBUSY;
+		}
+	}
+
+	for (wchan = 0; wchan < pwm->nchan; wchan++) {
+		dev = class_find_device(&pwm_class, NULL,
+					&pwm->channels[wchan],
+					__match_device);
+		if (dev) {
+			put_device(dev);
+			device_unregister(dev);
+		}
+	}
+
+	kfree(pwm->channels);
+	list_del(&pwm->list);
+	mutex_unlock(&device_list_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL(pwm_unregister);
+
+
+static struct pwm_device *
+__pwm_find_device(const char *bus_id)
+{
+	struct pwm_device *p;
+
+	list_for_each_entry(p, &pwm_device_list, list)
+	{
+		if (!strcmp(bus_id, p->bus_id))
+			return p;
+	}
+	return NULL;
+}
+
+
+static int
+__pwm_request_channel(struct pwm_channel *p,
+		      const char *requester)
+{
+	int ret;
+
+	if (test_and_set_bit(FLAG_REQUESTED, &p->flags))
+		return -EBUSY;
+
+	if (p->pwm->request) {
+		ret = p->pwm->request(p);
+		if (ret) {
+			clear_bit(FLAG_REQUESTED, &p->flags);
+			return ret;
+		}
+	}
+
+	p->requester = requester;
+	return 0;
+}
+
+
+struct pwm_channel *
+pwm_request(const char *bus_id,
+	    int chan,
+	    const char *requester)
+{
+	struct pwm_device *p;
+	int ret;
+
+	mutex_lock(&device_list_mutex);
+
+	p = __pwm_find_device(bus_id);
+	if (!p || chan >= p->nchan)
+		goto err_no_device;
+
+	if (!try_module_get(p->owner))
+		goto err_module_get_failed;
+
+	ret = __pwm_request_channel(&p->channels[chan], requester);
+	if (ret)
+		goto err_request_failed;
+
+	mutex_unlock(&device_list_mutex);
+
+	pr_debug("%s: %s:%d returns %p\n", __func__,
+		 bus_id, chan, &p->channels[chan]);
+
+	return &p->channels[chan];
+
+err_request_failed:
+	module_put(p->owner);
+err_module_get_failed:
+err_no_device:
+
+	mutex_unlock(&device_list_mutex);
+
+	pr_debug("%s: %s:%d returns NULL\n",
+		 __func__, bus_id, chan);
+
+	return NULL;
+}
+EXPORT_SYMBOL(pwm_request);
+
+
+void pwm_free(struct pwm_channel *p)
+{
+	mutex_lock(&device_list_mutex);
+
+	if (!test_and_clear_bit(FLAG_REQUESTED, &p->flags))
+		goto done;
+
+	pwm_stop(p);
+	pwm_unsynchronize(p, NULL);
+	pwm_set_handler(p, NULL, NULL);
+
+	if (p->pwm->free)
+		p->pwm->free(p);
+	module_put(p->pwm->owner);
+
+	pr_debug("%s: %s:%d free\n",
+		 __func__, p->pwm->bus_id, p->chan);
+
+done:
+	mutex_unlock(&device_list_mutex);
+}
+EXPORT_SYMBOL(pwm_free);
+
+
+unsigned long pwm_ns_to_ticks(struct pwm_channel *p,
+			      unsigned long nsecs)
+{
+	unsigned long long ticks;
+
+	ticks = nsecs;
+	ticks *= p->tick_hz;
+	do_div(ticks, 1000000000);
+	return ticks;
+}
+EXPORT_SYMBOL(pwm_ns_to_ticks);
+
+
+unsigned long pwm_ticks_to_ns(struct pwm_channel *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;
+}
+EXPORT_SYMBOL(pwm_ticks_to_ns);
+
+
+static void
+pwm_config_ns_to_ticks(struct pwm_channel *p,
+		       struct pwm_channel_config *c)
+{
+	if (c->config_mask & PWM_CONFIG_PERIOD_NS) {
+		c->period_ticks = pwm_ns_to_ticks(p, c->period_ns);
+		c->config_mask &= ~PWM_CONFIG_PERIOD_NS;
+		c->config_mask |= PWM_CONFIG_PERIOD_TICKS;
+	}
+
+	if (c->config_mask & PWM_CONFIG_DUTY_NS) {
+		c->duty_ticks = pwm_ns_to_ticks(p, c->duty_ns);
+		c->config_mask &= ~PWM_CONFIG_DUTY_NS;
+		c->config_mask |= PWM_CONFIG_DUTY_TICKS;
+	}
+}
+
+
+static void
+pwm_config_percent_to_ticks(struct pwm_channel *p,
+			    struct pwm_channel_config *c)
+{
+	if (c->config_mask & PWM_CONFIG_DUTY_PERCENT) {
+		if (c->config_mask & PWM_CONFIG_PERIOD_TICKS)
+			c->duty_ticks = c->period_ticks;
+		else
+			c->duty_ticks = p->period_ticks;
+
+		c->duty_ticks *= c->duty_percent;
+		c->duty_ticks /= 100;
+		c->config_mask &= ~PWM_CONFIG_DUTY_PERCENT;
+		c->config_mask |= PWM_CONFIG_DUTY_TICKS;
+	}
+}
+
+
+int pwm_config_nosleep(struct pwm_channel *p,
+		       struct pwm_channel_config *c)
+{
+	if (!p->pwm->config_nosleep)
+		return -EINVAL;
+
+	pwm_config_ns_to_ticks(p, c);
+	pwm_config_percent_to_ticks(p, c);
+
+	return p->pwm->config_nosleep(p, c);
+}
+EXPORT_SYMBOL(pwm_config_nosleep);
+
+
+int pwm_config(struct pwm_channel *p,
+	       struct pwm_channel_config *c)
+{
+	int ret = 0;
+
+	if (unlikely(!p->pwm->config)) {
+		pr_debug("%s: %s:%d has no config handler (-EINVAL)\n",
+			 __func__, p->pwm->bus_id, p->chan);
+		return -EINVAL;
+	}
+
+	pwm_config_ns_to_ticks(p, c);
+	pwm_config_percent_to_ticks(p, c);
+
+	switch (c->config_mask & (PWM_CONFIG_PERIOD_TICKS
+				  | PWM_CONFIG_DUTY_TICKS)) {
+	case PWM_CONFIG_PERIOD_TICKS:
+		if (p->duty_ticks > c->period_ticks) {
+			ret = -EINVAL;
+			goto err;
+		}
+		break;
+	case PWM_CONFIG_DUTY_TICKS:
+		if (p->period_ticks < c->duty_ticks) {
+			ret = -EINVAL;
+			goto err;
+		}
+		break;
+	case PWM_CONFIG_DUTY_TICKS | PWM_CONFIG_PERIOD_TICKS:
+		if (c->duty_ticks > c->period_ticks) {
+			ret = -EINVAL;
+			goto err;
+		}
+		break;
+	default:
+		break;
+	}
+
+err:
+	pr_debug("%s: config_mask %d period_ticks %lu duty_ticks %lu"
+		 " polarity %d duty_ns %lu period_ns %lu duty_percent %d\n",
+		 __func__, c->config_mask, c->period_ticks, c->duty_ticks,
+		 c->polarity, c->duty_ns, c->period_ns, c->duty_percent);
+
+	if (ret)
+		return ret;
+	return p->pwm->config(p, c);
+}
+EXPORT_SYMBOL(pwm_config);
+
+
+int pwm_period_ns(struct pwm_channel *p,
+		  unsigned long period_ns)
+{
+	struct pwm_channel_config c = {
+		.config_mask = PWM_CONFIG_PERIOD_TICKS,
+		.period_ticks = pwm_ns_to_ticks(p, period_ns),
+	};
+
+	return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_period_ns);
+
+
+int pwm_duty_ns(struct pwm_channel *p,
+		unsigned long duty_ns)
+{
+	struct pwm_channel_config c = {
+		.config_mask = PWM_CONFIG_DUTY_TICKS,
+		.duty_ticks = pwm_ns_to_ticks(p, duty_ns),
+	};
+	return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_duty_ns);
+
+
+int pwm_duty_percent(struct pwm_channel *p,
+		     int percent)
+{
+	struct pwm_channel_config c = {
+		.config_mask = PWM_CONFIG_DUTY_PERCENT,
+		.duty_percent = percent,
+	};
+	return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_duty_percent);
+
+
+int pwm_polarity(struct pwm_channel *p,
+		 int active_high)
+{
+	struct pwm_channel_config c = {
+		.config_mask = PWM_CONFIG_POLARITY,
+		.polarity = active_high,
+	};
+	return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_polarity);
+
+
+int pwm_start(struct pwm_channel *p)
+{
+	struct pwm_channel_config c = {
+		.config_mask = PWM_CONFIG_START,
+	};
+	return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_start);
+
+
+int pwm_stop(struct pwm_channel *p)
+{
+	struct pwm_channel_config c = {
+		.config_mask = PWM_CONFIG_STOP,
+	};
+	return pwm_config(p, &c);
+}
+EXPORT_SYMBOL(pwm_stop);
+
+
+int pwm_synchronize(struct pwm_channel *p,
+		    struct pwm_channel *to_p)
+{
+	if (p->pwm != to_p->pwm) {
+		/* TODO: support cross-device synchronization */
+		return -EINVAL;
+	}
+
+	if (!p->pwm->synchronize)
+		return -EINVAL;
+
+	return p->pwm->synchronize(p, to_p);
+}
+EXPORT_SYMBOL(pwm_synchronize);
+
+
+int pwm_unsynchronize(struct pwm_channel *p,
+		      struct pwm_channel *from_p)
+{
+	if (from_p && (p->pwm != from_p->pwm)) {
+		/* TODO: support cross-device synchronization */
+		return -EINVAL;
+	}
+
+	if (!p->pwm->unsynchronize)
+		return -EINVAL;
+
+	return p->pwm->unsynchronize(p, from_p);
+}
+EXPORT_SYMBOL(pwm_unsynchronize);
+
+
+static void pwm_handler(struct work_struct *w)
+{
+	struct pwm_channel *p = container_of(w, struct pwm_channel,
+					     handler_work);
+	if (p->handler && p->handler(p, p->handler_data))
+		pwm_stop(p);
+}
+
+
+static void __pwm_callback(struct pwm_channel *p)
+{
+	queue_work(pwm_handler_workqueue, &p->handler_work);
+	pr_debug("%s:%d handler %p scheduled with data %p\n",
+		 p->pwm->bus_id, p->chan, p->handler, p->handler_data);
+}
+
+
+int pwm_set_handler(struct pwm_channel *p,
+		    pwm_handler_t handler,
+		    void *data)
+{
+	if (p->pwm->set_callback) {
+		p->handler_data = data;
+		p->handler = handler;
+		INIT_WORK(&p->handler_work, pwm_handler);
+		return p->pwm->set_callback(p, handler ? __pwm_callback : NULL);
+	}
+	return -EINVAL;
+}
+EXPORT_SYMBOL(pwm_set_handler);
+
+
+static ssize_t pwm_run_store(struct device *dev,
+			     struct device_attribute *attr,
+			     const char *buf,
+			     size_t len)
+{
+	struct pwm_channel *p = dev_get_drvdata(dev);
+	if (sysfs_streq(buf, "1"))
+		pwm_start(p);
+	else if (sysfs_streq(buf, "0"))
+		pwm_stop(p);
+	return len;
+}
+static DEVICE_ATTR(run, 0200, NULL, pwm_run_store);
+
+
+static ssize_t pwm_duty_ns_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	struct pwm_channel *p = dev_get_drvdata(dev);
+	return sprintf(buf, "%lu\n", pwm_ticks_to_ns(p, p->duty_ticks));
+}
+
+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_channel *p = dev_get_drvdata(dev);
+
+	if (1 == sscanf(buf, "%lu", &duty_ns))
+		pwm_duty_ns(p, duty_ns);
+	return len;
+}
+static DEVICE_ATTR(duty_ns, 0644, pwm_duty_ns_show, pwm_duty_ns_store);
+
+
+static ssize_t pwm_period_ns_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	struct pwm_channel *p = dev_get_drvdata(dev);
+	return sprintf(buf, "%lu\n", pwm_ticks_to_ns(p, p->period_ticks));
+}
+
+
+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_channel *p = dev_get_drvdata(dev);
+
+	if (1 == sscanf(buf, "%lu", &period_ns))
+		pwm_period_ns(p, period_ns);
+	return len;
+}
+static DEVICE_ATTR(period_ns, 0644, pwm_period_ns_show, pwm_period_ns_store);
+
+
+static ssize_t pwm_polarity_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct pwm_channel *p = dev_get_drvdata(dev);
+	return sprintf(buf, "%d\n", p->active_low ? 0 : 1);
+}
+
+
+static ssize_t pwm_polarity_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf,
+				  size_t len)
+{
+	int polarity;
+	struct pwm_channel *p = dev_get_drvdata(dev);
+
+	if (1 == sscanf(buf, "%d", &polarity))
+		pwm_polarity(p, polarity);
+	return len;
+}
+static DEVICE_ATTR(polarity, 0644, pwm_polarity_show, pwm_polarity_store);
+
+
+static ssize_t pwm_request_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	struct pwm_channel *p = dev_get_drvdata(dev);
+	mutex_lock(&device_list_mutex);
+	__pwm_request_channel(p, "sysfs");
+	mutex_unlock(&device_list_mutex);
+
+	return sprintf(buf, "%s\n", p->requester);
+}
+
+
+static ssize_t pwm_request_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf,
+				 size_t len)
+{
+	struct pwm_channel *p = dev_get_drvdata(dev);
+	pwm_free(p);
+	return len;
+}
+static DEVICE_ATTR(request, 0644, pwm_request_show, pwm_request_store);
+
+
+static const struct attribute *pwm_attrs[] =
+{
+	&dev_attr_run.attr,
+	&dev_attr_polarity.attr,
+	&dev_attr_duty_ns.attr,
+	&dev_attr_period_ns.attr,
+	&dev_attr_request.attr,
+	NULL,
+};
+
+
+static const struct attribute_group pwm_device_attr_group = {
+	.attrs = (struct attribute **)pwm_attrs,
+};
+
+
+static int __pwm_create_sysfs(struct pwm_device *pwm)
+{
+	int ret = 0;
+	struct device *dev;
+	int wchan;
+
+	for (wchan = 0; wchan < pwm->nchan; wchan++) {
+		dev = device_create(&pwm_class, pwm->dev, MKDEV(0, 0),
+				    pwm->channels + wchan,
+				    "%s:%d", pwm->bus_id, wchan);
+		if (!dev)
+			goto err_dev_create;
+		ret = sysfs_create_group(&dev->kobj, &pwm_device_attr_group);
+		if (ret)
+			goto err_dev_group_create;
+	}
+
+	return ret;
+
+err_dev_group_create:
+err_dev_create:
+	/* TODO: undo all the successful device_create calls */
+	return -ENODEV;
+}
+
+
+static struct class_attribute pwm_class_attrs[] = {
+	__ATTR_NULL,
+};
+
+static struct class pwm_class = {
+	.name = "pwm",
+	.owner = THIS_MODULE,
+
+	.class_attrs = pwm_class_attrs,
+};
+
+
+static int __init pwm_init(void)
+{
+	int ret;
+
+	/* TODO: how to deal with devices that register very early? */
+
+	ret = class_register(&pwm_class);
+	if (ret < 0)
+		return ret;
+
+	pwm_handler_workqueue = create_workqueue("pwmd");
+
+	return 0;
+}
+postcore_initcall(pwm_init);