text: /*
   * Generic pwmlib implementation
   *
   * Copyright (C) 2011 Sascha Hauer <s.hauer@pengutronix.de>
   * Copyright (C) 2011-2012 Avionic Design GmbH
   *
   *  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.
   *
   *  You should have received a copy of the GNU General Public License
   *  along with this program; see the file COPYING.  If not, write to
   *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  #include <linux/module.h>
  #include <linux/pwm.h>
  #include <linux/radix-tree.h>
  #include <linux/list.h>
  #include <linux/mutex.h>
  #include <linux/err.h>
  #include <linux/slab.h>
  #include <linux/device.h>
  #include <linux/debugfs.h>
  #include <linux/seq_file.h>
  
  #include <dt-bindings/pwm/pwm.h>
  
  #define MAX_PWMS 1024
  
  static DEFINE_MUTEX(pwm_lookup_lock);
  static LIST_HEAD(pwm_lookup_list);
  static DEFINE_MUTEX(pwm_lock);
  static LIST_HEAD(pwm_chips);
  static DECLARE_BITMAP(allocated_pwms, MAX_PWMS);
  static RADIX_TREE(pwm_tree, GFP_KERNEL);
  
  static struct pwm_device *pwm_to_device(unsigned int pwm)
  {
  	return radix_tree_lookup(&pwm_tree, pwm);
  }
  
  static int alloc_pwms(int pwm, unsigned int count)
  {
  	unsigned int from = 0;
  	unsigned int start;
  
  	if (pwm >= MAX_PWMS)
  		return -EINVAL;
  
  	if (pwm >= 0)
  		from = pwm;
  
  	start = bitmap_find_next_zero_area(allocated_pwms, MAX_PWMS, from,
  					   count, 0);
  
  	if (pwm >= 0 && start != pwm)
  		return -EEXIST;
  
  	if (start + count > MAX_PWMS)
  		return -ENOSPC;
  
  	return start;
  }
  
  static void free_pwms(struct pwm_chip *chip)
  {
  	unsigned int i;
  
  	for (i = 0; i < chip->npwm; i++) {
  		struct pwm_device *pwm = &chip->pwms[i];
  		radix_tree_delete(&pwm_tree, pwm->pwm);
  	}
  
  	bitmap_clear(allocated_pwms, chip->base, chip->npwm);
  
  	kfree(chip->pwms);
  	chip->pwms = NULL;
  }
  
  static struct pwm_chip *pwmchip_find_by_name(const char *name)
  {
  	struct pwm_chip *chip;
  
  	if (!name)
  		return NULL;
  
  	mutex_lock(&pwm_lock);
  
  	list_for_each_entry(chip, &pwm_chips, list) {
  		const char *chip_name = dev_name(chip->dev);
  
  		if (chip_name && strcmp(chip_name, name) == 0) {
  			mutex_unlock(&pwm_lock);
  			return chip;
  		}
  	}
  
  	mutex_unlock(&pwm_lock);
  
  	return NULL;
  }
  
  static int pwm_device_request(struct pwm_device *pwm, const char *label)
  {
  	int err;
  
  	if (test_bit(PWMF_REQUESTED, &pwm->flags))
  		return -EBUSY;
  
  	if (!try_module_get(pwm->chip->ops->owner))
  		return -ENODEV;
  
  	if (pwm->chip->ops->request) {
  		err = pwm->chip->ops->request(pwm->chip, pwm);
  		if (err) {
  			module_put(pwm->chip->ops->owner);
  			return err;
  		}
  	}
  
  	set_bit(PWMF_REQUESTED, &pwm->flags);
  	pwm->label = label;
  
  	return 0;
  }
  
  struct pwm_device *
  of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
  {
  	struct pwm_device *pwm;
  
  	if (pc->of_pwm_n_cells < 3)
  		return ERR_PTR(-EINVAL);
  
  	if (args->args[0] >= pc->npwm)
  		return ERR_PTR(-EINVAL);
  
  	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
  	if (IS_ERR(pwm))
  		return pwm;
  
  	pwm_set_period(pwm, args->args[1]);
  
  	if (args->args[2] & PWM_POLARITY_INVERTED)
  		pwm_set_polarity(pwm, PWM_POLARITY_INVERSED);
  	else
  		pwm_set_polarity(pwm, PWM_POLARITY_NORMAL);
  
  	return pwm;
  }
  EXPORT_SYMBOL_GPL(of_pwm_xlate_with_flags);
  
  static struct pwm_device *
  of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
  {
  	struct pwm_device *pwm;
  
  	if (pc->of_pwm_n_cells < 2)
  		return ERR_PTR(-EINVAL);
  
  	if (args->args[0] >= pc->npwm)
  		return ERR_PTR(-EINVAL);
  
  	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
  	if (IS_ERR(pwm))
  		return pwm;
  
  	pwm_set_period(pwm, args->args[1]);
  
  	return pwm;
  }
  
  static void of_pwmchip_add(struct pwm_chip *chip)
  {
  	if (!chip->dev || !chip->dev->of_node)
  		return;
  
  	if (!chip->of_xlate) {
  		chip->of_xlate = of_pwm_simple_xlate;
  		chip->of_pwm_n_cells = 2;
  	}
  
  	of_node_get(chip->dev->of_node);
  }
  
  static void of_pwmchip_remove(struct pwm_chip *chip)
  {
  	if (chip->dev && chip->dev->of_node)
  		of_node_put(chip->dev->of_node);
  }
  
  /**
   * pwm_set_chip_data() - set private chip data for a PWM
   * @pwm: PWM device
   * @data: pointer to chip-specific data
   */
  int pwm_set_chip_data(struct pwm_device *pwm, void *data)
  {
  	if (!pwm)
  		return -EINVAL;
  
  	pwm->chip_data = data;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(pwm_set_chip_data);
  
  /**
   * pwm_get_chip_data() - get private chip data for a PWM
   * @pwm: PWM device
   */
  void *pwm_get_chip_data(struct pwm_device *pwm)
  {
  	return pwm ? pwm->chip_data : NULL;
  }
  EXPORT_SYMBOL_GPL(pwm_get_chip_data);
  
  /**
   * pwmchip_add() - register a new PWM chip
   * @chip: the PWM chip to add
   *
   * Register a new PWM chip. If chip->base < 0 then a dynamically assigned base
   * will be used.
   */
  int pwmchip_add(struct pwm_chip *chip)
  {
  	struct pwm_device *pwm;
  	unsigned int i;
  	int ret;
  
  	if (!chip || !chip->dev || !chip->ops || !chip->ops->config ||
  	    !chip->ops->enable || !chip->ops->disable)
  		return -EINVAL;
  
  	mutex_lock(&pwm_lock);
  
  	ret = alloc_pwms(chip->base, chip->npwm);
  	if (ret < 0)
  		goto out;
  
  	chip->pwms = kzalloc(chip->npwm * sizeof(*pwm), GFP_KERNEL);
  	if (!chip->pwms) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	chip->base = ret;
  
  	for (i = 0; i < chip->npwm; i++) {
  		pwm = &chip->pwms[i];
  
  		pwm->chip = chip;
  		pwm->pwm = chip->base + i;
  		pwm->hwpwm = i;
  
  		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
  	}
  
  	bitmap_set(allocated_pwms, chip->base, chip->npwm);
  
  	INIT_LIST_HEAD(&chip->list);
  	list_add(&chip->list, &pwm_chips);
  
  	ret = 0;
  
  	if (IS_ENABLED(CONFIG_OF))
  		of_pwmchip_add(chip);
  
  	pwmchip_sysfs_export(chip);
  
  out:
  	mutex_unlock(&pwm_lock);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(pwmchip_add);
  
  /**
   * pwmchip_remove() - remove a PWM chip
   * @chip: the PWM chip to remove
   *
   * Removes a PWM chip. This function may return busy if the PWM chip provides
   * a PWM device that is still requested.
   */
  int pwmchip_remove(struct pwm_chip *chip)
  {
  	unsigned int i;
  	int ret = 0;
  
  	mutex_lock(&pwm_lock);
  
  	for (i = 0; i < chip->npwm; i++) {
  		struct pwm_device *pwm = &chip->pwms[i];
  
  		if (test_bit(PWMF_REQUESTED, &pwm->flags)) {
  			ret = -EBUSY;
  			goto out;
  		}
  	}
  
  	list_del_init(&chip->list);
  
  	if (IS_ENABLED(CONFIG_OF))
  		of_pwmchip_remove(chip);
  
  	free_pwms(chip);
  
  	pwmchip_sysfs_unexport(chip);
  
  out:
  	mutex_unlock(&pwm_lock);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(pwmchip_remove);
  
  /**
   * pwm_request() - request a PWM device
   * @pwm_id: global PWM device index
   * @label: PWM device label
   *
   * This function is deprecated, use pwm_get() instead.
   */
  struct pwm_device *pwm_request(int pwm, const char *label)
  {
  	struct pwm_device *dev;
  	int err;
  
  	if (pwm < 0 || pwm >= MAX_PWMS)
  		return ERR_PTR(-EINVAL);
  
  	mutex_lock(&pwm_lock);
  
  	dev = pwm_to_device(pwm);
  	if (!dev) {
  		dev = ERR_PTR(-EPROBE_DEFER);
  		goto out;
  	}
  
  	err = pwm_device_request(dev, label);
  	if (err < 0)
  		dev = ERR_PTR(err);
  
  out:
  	mutex_unlock(&pwm_lock);
  
  	return dev;
  }
  EXPORT_SYMBOL_GPL(pwm_request);
  
  /**
   * pwm_request_from_chip() - request a PWM device relative to a PWM chip
   * @chip: PWM chip
   * @index: per-chip index of the PWM to request
   * @label: a literal description string of this PWM
   *
   * Returns the PWM at the given index of the given PWM chip. A negative error
   * code is returned if the index is not valid for the specified PWM chip or
   * if the PWM device cannot be requested.
   */
  struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
  					 unsigned int index,
  					 const char *label)
  {
  	struct pwm_device *pwm;
  	int err;
  
  	if (!chip || index >= chip->npwm)
  		return ERR_PTR(-EINVAL);
  
  	mutex_lock(&pwm_lock);
  	pwm = &chip->pwms[index];
  
  	err = pwm_device_request(pwm, label);
  	if (err < 0)
  		pwm = ERR_PTR(err);
  
  	mutex_unlock(&pwm_lock);
  	return pwm;
  }
  EXPORT_SYMBOL_GPL(pwm_request_from_chip);
  
  /**
   * pwm_free() - free a PWM device
   * @pwm: PWM device
   *
   * This function is deprecated, use pwm_put() instead.
   */
  void pwm_free(struct pwm_device *pwm)
  {
  	pwm_put(pwm);
  }
  EXPORT_SYMBOL_GPL(pwm_free);
  
  /**
   * pwm_config() - change a PWM device configuration
   * @pwm: PWM device
   * @duty_ns: "on" time (in nanoseconds)
   * @period_ns: duration (in nanoseconds) of one cycle
   */
  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;
  
  	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);
  
  /**
   * pwm_set_polarity() - configure the polarity of a PWM signal
   * @pwm: PWM device
   * @polarity: new polarity of the PWM signal
   *
   * Note that the polarity cannot be configured while the PWM device is enabled
   */
  int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
  {
  	int err;
  
  	if (!pwm || !pwm->chip->ops)
  		return -EINVAL;
  
  	if (!pwm->chip->ops->set_polarity)
  		return -ENOSYS;
  
  	if (test_bit(PWMF_ENABLED, &pwm->flags))
  		return -EBUSY;
  
  	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);
  
  /**
   * pwm_enable() - start a PWM output toggling
   * @pwm: PWM device
   */
  int pwm_enable(struct pwm_device *pwm)
  {
  	if (pwm && !test_and_set_bit(PWMF_ENABLED, &pwm->flags))
  		return pwm->chip->ops->enable(pwm->chip, pwm);
  
  	return pwm ? 0 : -EINVAL;
  }
  EXPORT_SYMBOL_GPL(pwm_enable);
  
  /**
   * pwm_disable() - stop a PWM output toggling
   * @pwm: PWM device
   */
  void pwm_disable(struct pwm_device *pwm)
  {
  	if (pwm && test_and_clear_bit(PWMF_ENABLED, &pwm->flags))
  		pwm->chip->ops->disable(pwm->chip, pwm);
  }
  EXPORT_SYMBOL_GPL(pwm_disable);
  
  static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
  {
  	struct pwm_chip *chip;
  
  	mutex_lock(&pwm_lock);
  
  	list_for_each_entry(chip, &pwm_chips, list)
  		if (chip->dev && chip->dev->of_node == np) {
  			mutex_unlock(&pwm_lock);
  			return chip;
  		}
  
  	mutex_unlock(&pwm_lock);
  
  	return ERR_PTR(-EPROBE_DEFER);
  }
  
  /**
   * of_pwm_get() - request a PWM via the PWM framework
   * @np: device node to get the PWM from
   * @con_id: consumer name
   *
   * Returns the PWM device parsed from the phandle and index specified in the
   * "pwms" property of a device tree node or a negative error-code on failure.
   * Values parsed from the device tree are stored in the returned PWM device
   * object.
   *
   * If con_id is NULL, the first PWM device listed in the "pwms" property will
   * be requested. Otherwise the "pwm-names" property is used to do a reverse
   * lookup of the PWM index. This also means that the "pwm-names" property
   * becomes mandatory for devices that look up the PWM device via the con_id
   * parameter.
   */
  struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
  {
  	struct pwm_device *pwm = NULL;
  	struct of_phandle_args args;
  	struct pwm_chip *pc;
  	int index = 0;
  	int err;
  
  	if (con_id) {
  		index = of_property_match_string(np, "pwm-names", con_id);
  		if (index < 0)
  			return ERR_PTR(index);
  	}
  
  	err = of_parse_phandle_with_args(np, "pwms", "#pwm-cells", index,
  					 &args);
  	if (err) {
  		pr_debug("%s(): can't parse \"pwms\" property\n", __func__);
  		return ERR_PTR(err);
  	}
  
  	pc = of_node_to_pwmchip(args.np);
  	if (IS_ERR(pc)) {
  		pr_debug("%s(): PWM chip not found\n", __func__);
  		pwm = ERR_CAST(pc);
  		goto put;
  	}
  
  	if (args.args_count != pc->of_pwm_n_cells) {
  		pr_debug("%s: wrong #pwm-cells for %s\n", np->full_name,
  			 args.np->full_name);
  		pwm = ERR_PTR(-EINVAL);
  		goto put;
  	}
  
  	pwm = pc->of_xlate(pc, &args);
  	if (IS_ERR(pwm))
  		goto put;
  
  	/*
  	 * If a consumer name was not given, try to look it up from the
  	 * "pwm-names" property if it exists. Otherwise use the name of
  	 * the user device node.
  	 */
  	if (!con_id) {
  		err = of_property_read_string_index(np, "pwm-names", index,
  						    &con_id);
  		if (err < 0)
  			con_id = np->name;
  	}
  
  	pwm->label = con_id;
  
  put:
  	of_node_put(args.np);
  
  	return pwm;
  }
  EXPORT_SYMBOL_GPL(of_pwm_get);
  
  /**
   * pwm_add_table() - register PWM device consumers
   * @table: array of consumers to register
   * @num: number of consumers in table
   */
  void __init pwm_add_table(struct pwm_lookup *table, size_t num)
  {
  	mutex_lock(&pwm_lookup_lock);
  
  	while (num--) {
  		list_add_tail(&table->list, &pwm_lookup_list);
  		table++;
  	}
  
  	mutex_unlock(&pwm_lookup_lock);
  }
  
  /**
   * pwm_get() - look up and request a PWM device
   * @dev: device for PWM consumer
   * @con_id: consumer name
   *
   * Lookup is first attempted using DT. If the device was not instantiated from
   * a device tree, a PWM chip and a relative index is looked up via a table
   * supplied by board setup code (see pwm_add_table()).
   *
   * Once a PWM chip has been found the specified PWM device will be requested
   * and is ready to be used.
   */
  struct pwm_device *pwm_get(struct device *dev, const char *con_id)
  {
  	struct pwm_device *pwm = ERR_PTR(-EPROBE_DEFER);
  	const char *dev_id = dev ? dev_name(dev) : NULL;
  	struct pwm_chip *chip = NULL;
  	unsigned int index = 0;
  	unsigned int best = 0;
  	struct pwm_lookup *p;
  	unsigned int match;
  
  	/* look up via DT first */
  	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
  		return of_pwm_get(dev->of_node, con_id);
  
  	/*
  	 * We look up the provider in the static table typically provided by
  	 * board setup code. We first try to lookup the consumer device by
  	 * name. If the consumer device was passed in as NULL or if no match
  	 * was found, we try to find the consumer by directly looking it up
  	 * by name.
  	 *
  	 * If a match is found, the provider PWM chip is looked up by name
  	 * and a PWM device is requested using the PWM device per-chip index.
  	 *
  	 * The lookup algorithm was shamelessly taken from the clock
  	 * framework:
  	 *
  	 * We do slightly fuzzy matching here:
  	 *  An entry with a NULL ID is assumed to be a wildcard.
  	 *  If an entry has a device ID, it must match
  	 *  If an entry has a connection ID, it must match
  	 * Then we take the most specific entry - with the following order
  	 * of precedence: dev+con > dev only > con only.
  	 */
  	mutex_lock(&pwm_lookup_lock);
  
  	list_for_each_entry(p, &pwm_lookup_list, list) {
  		match = 0;
  
  		if (p->dev_id) {
  			if (!dev_id || strcmp(p->dev_id, dev_id))
  				continue;
  
  			match += 2;
  		}
  
  		if (p->con_id) {
  			if (!con_id || strcmp(p->con_id, con_id))
  				continue;
  
  			match += 1;
  		}
  
  		if (match > best) {
  			chip = pwmchip_find_by_name(p->provider);
  			index = p->index;
  
  			if (match != 3)
  				best = match;
  			else
  				break;
  		}
  	}
  
  	if (chip)
  		pwm = pwm_request_from_chip(chip, index, con_id ?: dev_id);
  
  	mutex_unlock(&pwm_lookup_lock);
  
  	return pwm;
  }
  EXPORT_SYMBOL_GPL(pwm_get);
  
  /**
   * pwm_put() - release a PWM device
   * @pwm: PWM device
   */
  void pwm_put(struct pwm_device *pwm)
  {
  	if (!pwm)
  		return;
  
  	mutex_lock(&pwm_lock);
  
  	if (!test_and_clear_bit(PWMF_REQUESTED, &pwm->flags)) {
  		pr_warn("PWM device already freed\n");
  		goto out;
  	}
  
  	if (pwm->chip->ops->free)
  		pwm->chip->ops->free(pwm->chip, pwm);
  
  	pwm->label = NULL;
  
  	module_put(pwm->chip->ops->owner);
  out:
  	mutex_unlock(&pwm_lock);
  }
  EXPORT_SYMBOL_GPL(pwm_put);
  
  static void devm_pwm_release(struct device *dev, void *res)
  {
  	pwm_put(*(struct pwm_device **)res);
  }
  
  /**
   * devm_pwm_get() - resource managed pwm_get()
   * @dev: device for PWM consumer
   * @con_id: consumer name
   *
   * This function performs like pwm_get() but the acquired PWM device will
   * automatically be released on driver detach.
   */
  struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id)
  {
  	struct pwm_device **ptr, *pwm;
  
  	ptr = devres_alloc(devm_pwm_release, sizeof(*ptr), GFP_KERNEL);
  	if (!ptr)
  		return ERR_PTR(-ENOMEM);
  
  	pwm = pwm_get(dev, con_id);
  	if (!IS_ERR(pwm)) {
  		*ptr = pwm;
  		devres_add(dev, ptr);
  	} else {
  		devres_free(ptr);
  	}
  
  	return pwm;
  }
  EXPORT_SYMBOL_GPL(devm_pwm_get);
  
  /**
   * devm_of_pwm_get() - resource managed of_pwm_get()
   * @dev: device for PWM consumer
   * @np: device node to get the PWM from
   * @con_id: consumer name
   *
   * This function performs like of_pwm_get() but the acquired PWM device will
   * automatically be released on driver detach.
   */
  struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np,
  				   const char *con_id)
  {
  	struct pwm_device **ptr, *pwm;
  
  	ptr = devres_alloc(devm_pwm_release, sizeof(*ptr), GFP_KERNEL);
  	if (!ptr)
  		return ERR_PTR(-ENOMEM);
  
  	pwm = of_pwm_get(np, con_id);
  	if (!IS_ERR(pwm)) {
  		*ptr = pwm;
  		devres_add(dev, ptr);
  	} else {
  		devres_free(ptr);
  	}
  
  	return pwm;
  }
  EXPORT_SYMBOL_GPL(devm_of_pwm_get);
  
  static int devm_pwm_match(struct device *dev, void *res, void *data)
  {
  	struct pwm_device **p = res;
  
  	if (WARN_ON(!p || !*p))
  		return 0;
  
  	return *p == data;
  }
  
  /**
   * devm_pwm_put() - resource managed pwm_put()
   * @dev: device for PWM consumer
   * @pwm: PWM device
   *
   * Release a PWM previously allocated using devm_pwm_get(). Calling this
   * function is usually not needed because devm-allocated resources are
   * automatically released on driver detach.
   */
  void devm_pwm_put(struct device *dev, struct pwm_device *pwm)
  {
  	WARN_ON(devres_release(dev, devm_pwm_release, devm_pwm_match, pwm));
  }
  EXPORT_SYMBOL_GPL(devm_pwm_put);
  
  /**
    * pwm_can_sleep() - report whether PWM access will sleep
    * @pwm: PWM device
    *
    * It returns true if accessing the PWM can sleep, false otherwise.
    */
  bool pwm_can_sleep(struct pwm_device *pwm)
  {
  	return pwm->chip->can_sleep;
  }
  EXPORT_SYMBOL_GPL(pwm_can_sleep);
  
  #ifdef CONFIG_DEBUG_FS
  static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
  {
  	unsigned int i;
  
  	for (i = 0; i < chip->npwm; i++) {
  		struct pwm_device *pwm = &chip->pwms[i];
  
  		seq_printf(s, " pwm-%-3d (%-20.20s):", i, pwm->label);
  
  		if (test_bit(PWMF_REQUESTED, &pwm->flags))
  			seq_puts(s, " requested");
  
  		if (test_bit(PWMF_ENABLED, &pwm->flags))
  			seq_puts(s, " enabled");
  
  		seq_puts(s, "\n");
  	}
  }
  
  static void *pwm_seq_start(struct seq_file *s, loff_t *pos)
  {
  	mutex_lock(&pwm_lock);
  	s->private = "";
  
  	return seq_list_start(&pwm_chips, *pos);
  }
  
  static void *pwm_seq_next(struct seq_file *s, void *v, loff_t *pos)
  {
  	s->private = "\n";
  
  	return seq_list_next(v, &pwm_chips, pos);
  }
  
  static void pwm_seq_stop(struct seq_file *s, void *v)
  {
  	mutex_unlock(&pwm_lock);
  }
  
  static int pwm_seq_show(struct seq_file *s, void *v)
  {
  	struct pwm_chip *chip = list_entry(v, struct pwm_chip, list);
  
  	seq_printf(s, "%s%s/%s, %d PWM device%s\n", (char *)s->private,
  		   chip->dev->bus ? chip->dev->bus->name : "no-bus",
  		   dev_name(chip->dev), chip->npwm,
  		   (chip->npwm != 1) ? "s" : "");
  
  	if (chip->ops->dbg_show)
  		chip->ops->dbg_show(chip, s);
  	else
  		pwm_dbg_show(chip, s);
  
  	return 0;
  }
  
  static const struct seq_operations pwm_seq_ops = {
  	.start = pwm_seq_start,
  	.next = pwm_seq_next,
  	.stop = pwm_seq_stop,
  	.show = pwm_seq_show,
  };
  
  static int pwm_seq_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &pwm_seq_ops);
  }
  
  static const struct file_operations pwm_debugfs_ops = {
  	.owner = THIS_MODULE,
  	.open = pwm_seq_open,
  	.read = seq_read,
  	.llseek = seq_lseek,
  	.release = seq_release,
  };
  
  static int __init pwm_debugfs_init(void)
  {
  	debugfs_create_file("pwm", S_IFREG | S_IRUGO, NULL, NULL,
  			    &pwm_debugfs_ops);
  
  	return 0;
  }
  
  subsys_initcall(pwm_debugfs_init);
  #endif /* CONFIG_DEBUG_FS */
  