Message-ID: <20161004193713.GA26304@roeck-us.net>
Date:   Tue, 4 Oct 2016 12:37:13 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Jean Delvare <jdelvare@...e.de>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Punit Agrawal <punit.agrawal@....com>,
        linux-pm@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/9] hwmon: (core) New hwmon registration API

Hi Jean,

On Tue, Oct 04, 2016 at 10:45:59AM +0200, Jean Delvare wrote:
> Hi Guenter,
> 
> I see this patch is upstream now, but I had started reviewing it and
> maybe some of my comments are still relevant.
> 
As always, I appreciate the feedback. I'll be happy to submit follow-up
patches to address any concerns.

> It's not meant to be a complete review, which is why I had not sent it
> yet :-(
> 
> Also I did not follow the first iterations of this patchset so my
> apologies if I raise points which have already been discussed.
> 
> May I ask if any other subsystem is already doing anything like that?
> 
Depends what you mean with "anything like that". The API is inspired by
the iio API and a little by the thermal API. The details are probably
unique, though.

> FYI I gave a presentation about the hwmon device registration API
> evolution last week at Kernel Recipes [1] in Paris and mentioned this
> proposal.
> 
> [1] https://kernel-recipes.org/en/2016/
> 
> On dim., 2016-07-24 at 20:32 -0700, Guenter Roeck wrote:
> > Up to now, each hwmon driver has to implement its own sysfs attributes.
> > This requires a lot of template code, and distracts from the driver's core
> > function to read and write chip registers.
> > 
> > To be able to reduce driver complexity, move sensor attribute handling
> > and thermal zone registration into hwmon core. By using the new API,
> > driver code and data size is typically reduced by 20-70%, depending
> > on driver complexity and the number of sysfs attributes supported.
> 
> I looked at the diffstats for the drivers you have already converted and
> couldn't see any such huge improvement... Some drivers appear to be even
> larger after conversion?
> 
The above refers to code and data sizes.

> > With this patch, the new API only supports thermal sensors. Support for
> > other sensor types will be added with subsequent patches.
> > 
> > Acked-by: Punit Agrawal <punit.agrawal@....com>
> > Reviewed-by: Jonathan Cameron <jic23@...nel.org>
> > Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> > ---
> > v3:
> > - Thermal registration depends on IS_REACHABLE(CONFIG_THERMAL) and
> >   CONFIG_THERMAL_OF.
> > v2:
> > - Document callback function parameters of struct hwmon_ops in
> >   include/linux/hwmon.h.
> > - Clarify that the is_visible() callback is mandatory.
> > - Initialize device attribute read/write callback functions unconditionally.
> > - If an attribute has no template string, treat it as invisible, not as
> >   error. Affected are virtual attributes such as HWMON_C_REGISTER_TZ.
> > - Added newline to improve readability.
> > 
> > Review comments not addressed:
> > - Stick with u32 for attribute masks. We could use u64, but it is currently
> >   not needed, and changing it later would be straightforward.
> > - Do not use for_each_set_bit() to walk attribute masks.
> >   for_each_set_bit() expects a pointer to an unsigned long as argument,
> >   which would make it difficult to switch to u64 attribute masks if/when
> >   needed.
> > 
> >  drivers/hwmon/hwmon.c | 485 +++++++++++++++++++++++++++++++++++++++++++++++---
> >  include/linux/hwmon.h | 148 +++++++++++++++
> >  2 files changed, 606 insertions(+), 27 deletions(-)
> > 
> > diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
> > index 649a68d119b4..3e4cc442a089 100644
> > --- a/drivers/hwmon/hwmon.c
> > +++ b/drivers/hwmon/hwmon.c
> 
> I believe it would make sense to add you copyright at the top of the
> file. That's a pretty big change with lots of code.
> 
I don't really feel too strong about that. But, sure, can do.

> > @@ -12,6 +12,7 @@
> >  
> >  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> >  
> > +#include <linux/bitops.h>
> >  #include <linux/device.h>
> >  #include <linux/err.h>
> >  #include <linux/gfp.h>
> > @@ -21,6 +22,7 @@
> >  #include <linux/pci.h>
> >  #include <linux/slab.h>
> >  #include <linux/string.h>
> > +#include <linux/thermal.h>
> >  
> >  #define HWMON_ID_PREFIX "hwmon"
> >  #define HWMON_ID_FORMAT HWMON_ID_PREFIX "%d"
> > @@ -28,9 +30,35 @@
> >  struct hwmon_device {
> >  	const char *name;
> >  	struct device dev;
> > +	const struct hwmon_chip_info *chip;
> > +
> > +	struct attribute_group group;
> > +	const struct attribute_group **groups;
> >  };
> > +
> >  #define to_hwmon_device(d) container_of(d, struct hwmon_device, dev)
> >  
> > +struct hwmon_device_attribute {
> > +	struct device_attribute dev_attr;
> > +	const struct hwmon_ops *ops;
> > +	enum hwmon_sensor_types type;
> > +	u32 attr;
> > +	int index;
> > +};
> > +
> > +#define to_hwmon_attr(d) \
> > +	container_of(d, struct hwmon_device_attribute, dev_attr)
> > +
> > +/*
> > + * Thermal zone information
> > + * In addition to the reference to the hwmon device,
> > + * also provides the sensor index.
> > + */
> > +struct hwmon_thermal_data {
> > +	struct hwmon_device *hwdev;	/* Reference to hwmon device */
> > +	int index;			/* sensor index */
> > +};
> > +
> >  static ssize_t
> >  show_name(struct device *dev, struct device_attribute *attr, char *buf)
> >  {
> > @@ -78,25 +106,286 @@ static struct class hwmon_class = {
> >  
> >  static DEFINE_IDA(hwmon_ida);
> >  
> > -/**
> > - * hwmon_device_register_with_groups - register w/ hwmon
> > - * @dev: the parent device
> > - * @name: hwmon name attribute
> > - * @drvdata: driver data to attach to created device
> > - * @groups: List of attribute groups to create
> > - *
> > - * hwmon_device_unregister() must be called when the device is no
> > - * longer needed.
> > - *
> > - * Returns the pointer to the new device.
> > - */
> > -struct device *
> > -hwmon_device_register_with_groups(struct device *dev, const char *name,
> > -				  void *drvdata,
> > -				  const struct attribute_group **groups)
> > +/* Thermal zone handling */
> > +
> > +#if IS_REACHABLE(CONFIG_THERMAL) && defined(CONFIG_THERMAL_OF)
> > +static int hwmon_thermal_get_temp(void *data, int *temp)
> > +{
> > +	struct hwmon_thermal_data *tdata = data;
> > +	struct hwmon_device *hwdev = tdata->hwdev;
> > +	int ret;
> > +	long t;
> > +
> > +	ret = hwdev->chip->ops->read(&hwdev->dev, hwmon_temp, hwmon_temp_input,
> > +				     tdata->index, &t);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	*temp = t;
> > +
> > +	return 0;
> > +}
> > +
> > +static struct thermal_zone_of_device_ops hwmon_thermal_ops = {
> > +	.get_temp = hwmon_thermal_get_temp,
> > +};
> > +
> > +static int hwmon_thermal_add_sensor(struct device *dev,
> > +				    struct hwmon_device *hwdev, int index)
> > +{
> > +	struct hwmon_thermal_data *tdata;
> > +
> > +	tdata = devm_kzalloc(dev, sizeof(*tdata), GFP_KERNEL);
> > +	if (!tdata)
> > +		return -ENOMEM;
> > +
> > +	tdata->hwdev = hwdev;
> > +	tdata->index = index;
> > +
> > +	devm_thermal_zone_of_sensor_register(&hwdev->dev, index, tdata,
> > +					     &hwmon_thermal_ops);
> > +
> > +	return 0;
> > +}
> > +#else
> > +static int hwmon_thermal_add_sensor(struct device *dev,
> > +				    struct hwmon_device *hwdev, int index)
> > +{
> > +	return 0;
> > +}
> > +#endif /* IS_REACHABLE(CONFIG_THERMAL) && defined(CONFIG_THERMAL_OF) */
> > +
> > +/* sysfs attribute management */
> > +
> > +static ssize_t hwmon_attr_show(struct device *dev,
> > +			       struct device_attribute *devattr, char *buf)
> > +{
> > +	struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
> > +	long val;
> > +	int ret;
> > +
> > +	ret = hattr->ops->read(dev, hattr->type, hattr->attr, hattr->index,
> > +			       &val);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return sprintf(buf, "%ld\n", val);
> > +}
> > +
> > +static ssize_t hwmon_attr_store(struct device *dev,
> > +				struct device_attribute *devattr,
> > +				const char *buf, size_t count)
> > +{
> > +	struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
> > +	long val;
> > +	int ret;
> > +
> > +	ret = kstrtol(buf, 10, &val);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	ret = hattr->ops->write(dev, hattr->type, hattr->attr, hattr->index,
> > +				val);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return count;
> > +}
> > +
> > +static int hwmon_attr_base(enum hwmon_sensor_types type)
> > +{
> > +	if (type == hwmon_in)
> > +		return 0;
> > +	return 1;
> > +}
> > +
> > +static struct attribute *hwmon_genattr(struct device *dev,
> > +				       const void *drvdata,
> > +				       enum hwmon_sensor_types type,
> > +				       u32 attr,
> > +				       int index,
> > +				       const char *template,
> > +				       const struct hwmon_ops *ops)
> > +{
> > +	struct hwmon_device_attribute *hattr;
> > +	struct device_attribute *dattr;
> > +	struct attribute *a;
> > +	umode_t mode;
> > +	char *name;
> > +
> > +	/* The attribute is invisible if there is no template string */
> > +	if (!template)
> > +		return ERR_PTR(-ENOENT);
> > +
> > +	mode = ops->is_visible(drvdata, type, attr, index);
> 
> Any reason why you don't simply attach the provided ->is_visible to the
> attribute group and let the driver core do the work?
> 
Parameter are all different
	umode_t (*is_visible)(const void *drvdata, enum hwmon_sensor_types type,
	                              u32 attr, int channel);
vs.
	umode_t (*is_visible)(struct kobject *, struct attribute *, int);

> > +		return ERR_PTR(-ENOENT);
> > +
> > +	if ((mode & S_IRUGO) && !ops->read)
> > +		return ERR_PTR(-EINVAL);
> > +	if ((mode & S_IWUGO) && !ops->write)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	if (type == hwmon_chip) {
> 
> This needs a comment. It's not obvious what "hwmon_chip" is supposed to
> represent. From what I understand, maybe "hwmon_unique" would be a more
> appropriate name.
> 
Those are meant to be for attributes which apply to the entire chip.
Not sure if 'hwmon_unique' would reflect that better.
>From the documentation:
	"A virtual sensor type, used to describe attributes
	 which apply to the entire chip"

Do you have an idea for a better description ?

> > +		name = (char *)template;
> > +	} else {
> > +		name = devm_kzalloc(dev, strlen(template) + 16, GFP_KERNEL);
> > +		if (!name)
> > +			return ERR_PTR(-ENOMEM);
> > +		scnprintf(name, strlen(template) + 16, template,
> > +			  index + hwmon_attr_base(type));
> > +	}
> > +
> > +	hattr = devm_kzalloc(dev, sizeof(*hattr), GFP_KERNEL);
> > +	if (!hattr)
> > +		return ERR_PTR(-ENOMEM);
> 
> So basically you are doing 1 or 2 memory allocations for every
> attribute? Looks quite bad from a memory fragmentation
> perspective :-( Not to mention performance. Given that you have all the
> data at hand before you start, can't you preallocate an array with the
> right number of hattr and pick from it? That would at least solve half
> of the problem.
> 
> Something similar for string allocation may work too, although it's
> somewhat more complex due to the variable length. But I think the
> abituguru3 driver is doing it right, so maybe you can too.
> 
I'll look into it.

> > +
> > +	hattr->type = type;
> > +	hattr->attr = attr;
> > +	hattr->index = index;
> > +	hattr->ops = ops;
> > +
> > +	dattr = &hattr->dev_attr;
> > +	dattr->show = hwmon_attr_show;
> > +	dattr->store = hwmon_attr_store;
> > +
> > +	a = &dattr->attr;
> > +	sysfs_attr_init(a);
> > +	a->name = name;
> > +	a->mode = mode;
> > +
> > +	return a;
> > +}
> > +
> > +static const char * const hwmon_chip_attr_templates[] = {
> > +	[hwmon_chip_temp_reset_history] = "temp_reset_history",
> > +	[hwmon_chip_update_interval] = "update_interval",
> > +	[hwmon_chip_alarms] = "alarms",
> > +};
> > +
> > +static const char * const hwmon_temp_attr_templates[] = {
> > +	[hwmon_temp_input] = "temp%d_input",
> > +	[hwmon_temp_type] = "temp%d_type",
> > +	[hwmon_temp_lcrit] = "temp%d_lcrit",
> > +	[hwmon_temp_lcrit_hyst] = "temp%d_lcrit_hyst",
> > +	[hwmon_temp_min] = "temp%d_min",
> > +	[hwmon_temp_min_hyst] = "temp%d_min_hyst",
> > +	[hwmon_temp_max] = "temp%d_max",
> > +	[hwmon_temp_max_hyst] = "temp%d_max_hyst",
> > +	[hwmon_temp_crit] = "temp%d_crit",
> > +	[hwmon_temp_crit_hyst] = "temp%d_crit_hyst",
> > +	[hwmon_temp_emergency] = "temp%d_emergency",
> > +	[hwmon_temp_emergency_hyst] = "temp%d_emergency_hyst",
> > +	[hwmon_temp_alarm] = "temp%d_alarm",
> > +	[hwmon_temp_lcrit_alarm] = "temp%d_lcrit_alarm",
> > +	[hwmon_temp_min_alarm] = "temp%d_min_alarm",
> > +	[hwmon_temp_max_alarm] = "temp%d_max_alarm",
> > +	[hwmon_temp_crit_alarm] = "temp%d_crit_alarm",
> > +	[hwmon_temp_emergency_alarm] = "temp%d_emergency_alarm",
> > +	[hwmon_temp_fault] = "temp%d_fault",
> > +	[hwmon_temp_offset] = "temp%d_offset",
> > +	[hwmon_temp_label] = "temp%d_label",
> > +	[hwmon_temp_lowest] = "temp%d_lowest",
> > +	[hwmon_temp_highest] = "temp%d_highest",
> > +	[hwmon_temp_reset_history] = "temp%d_reset_history",
> > +};
> > +
> 
> This starts looking a lot like libsensors' code ;-)
> 
> > +static const char * const *__templates[] = {
> > +	[hwmon_chip] = hwmon_chip_attr_templates,
> > +	[hwmon_temp] = hwmon_temp_attr_templates,
> > +};
> > +
> > +static const int __templates_size[] = {
> > +	[hwmon_chip] = ARRAY_SIZE(hwmon_chip_attr_templates),
> > +	[hwmon_temp] = ARRAY_SIZE(hwmon_temp_attr_templates),
> > +};
> > +
> > +static int hwmon_num_channel_attrs(const struct hwmon_channel_info *info)
> > +{
> > +	int i, n;
> > +
> > +	for (i = n = 0; info->config[i]; i++)
> > +		n += hweight32(info->config[i]);
> > +
> > +	return n;
> > +}
> > +
> > +static int hwmon_genattrs(struct device *dev,
> > +			  const void *drvdata,
> > +			  struct attribute **attrs,
> > +			  const struct hwmon_ops *ops,
> > +			  const struct hwmon_channel_info *info)
> > +{
> > +	const char * const *templates;
> > +	int template_size;
> > +	int i, aindex = 0;
> > +
> > +	if (info->type >= ARRAY_SIZE(__templates))
> > +		return -EINVAL;
> > +
> > +	templates = __templates[info->type];
> > +	template_size = __templates_size[info->type];
> > +
> > +	for (i = 0; info->config[i]; i++) {
> > +		u32 attr_mask = info->config[i];
> > +		u32 attr;
> > +
> > +		while (attr_mask) {
> > +			struct attribute *a;
> > +
> > +			attr = __ffs(attr_mask);
> > +			attr_mask &= ~BIT(attr);
> > +			if (attr >= template_size)
> > +				return -EINVAL;
> > +			a = hwmon_genattr(dev, drvdata, info->type, attr, i,
> > +					  templates[attr], ops);
> > +			if (IS_ERR(a)) {
> > +				if (PTR_ERR(a) != -ENOENT)
> > +					return PTR_ERR(a);
> > +				continue;
> > +			}
> > +			attrs[aindex++] = a;
> > +		}
> > +	}
> > +	return aindex;
> > +}
> > +
> > +static struct attribute **
> > +__hwmon_create_attrs(struct device *dev, const void *drvdata,
> > +		     const struct hwmon_chip_info *chip)
> > +{
> > +	int ret, i, aindex = 0, nattrs = 0;
> > +	struct attribute **attrs;
> > +
> > +	for (i = 0; chip->info[i]; i++)
> > +		nattrs += hwmon_num_channel_attrs(chip->info[i]);
> > +
> > +	if (nattrs == 0)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	attrs = devm_kcalloc(dev, nattrs + 1, sizeof(*attrs), GFP_KERNEL);
> > +	if (!attrs)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	for (i = 0; chip->info[i]; i++) {
> > +		ret = hwmon_genattrs(dev, drvdata, &attrs[aindex], chip->ops,
> > +				     chip->info[i]);
> > +		if (ret < 0)
> > +			return ERR_PTR(ret);
> > +		aindex += ret;
> > +	}
> > +
> > +	return attrs;
> > +}
> > +
> > +static struct device *
> > +__hwmon_device_register(struct device *dev, const char *name, void *drvdata,
> > +			const struct hwmon_chip_info *chip,
> > +			const struct attribute_group **groups)
> >  {
> >  	struct hwmon_device *hwdev;
> > -	int err, id;
> > +	struct device *hdev;
> > +	int i, j, err, id;
> >  
> >  	/* Do not accept invalid characters in hwmon name attribute */
> >  	if (name && (!strlen(name) || strpbrk(name, "-* \t\n")))
> > @@ -112,28 +401,128 @@ hwmon_device_register_with_groups(struct device *dev, const char *name,
> >  		goto ida_remove;
> >  	}
> >  
> > +	hdev = &hwdev->dev;
> > +
> > +	if (chip && chip->ops->is_visible) {
> 
> is_visible is documented as mandatory, so why would this check be needed
> (and not result in an error if failed?)
> 
Let me check. I don't recall if the documentation is at fault or the
code.

> > +		struct attribute **attrs;
> > +		int ngroups = 2;
> 
> I'd appreciate a comment here.
> 
Sure.

> > +
> > +		if (groups)
> > +			for (i = 0; groups[i]; i++)
> > +				ngroups++;
> > +
> > +		hwdev->groups = devm_kcalloc(dev, ngroups, sizeof(*groups),
> > +					     GFP_KERNEL);
> > +		if (!hwdev->groups)
> > +			return ERR_PTR(-ENOMEM);
> > +
> > +		attrs = __hwmon_create_attrs(dev, drvdata, chip);
> > +		if (IS_ERR(attrs)) {
> > +			err = PTR_ERR(attrs);
> > +			goto free_hwmon;
> > +		}
> > +
> > +		hwdev->group.attrs = attrs;
> > +		ngroups = 0;
> > +		hwdev->groups[ngroups++] = &hwdev->group;
> > +
> > +		if (groups) {
> > +			for (i = 0; groups[i]; i++)
> > +				hwdev->groups[ngroups++] = groups[i];
> > +		}
> > +
> > +		hdev->groups = hwdev->groups;
> > +	} else {
> > +		hdev->groups = groups;
> > +	}
> > +
> >  	hwdev->name = name;
> > -	hwdev->dev.class = &hwmon_class;
> > -	hwdev->dev.parent = dev;
> > -	hwdev->dev.groups = groups;
> > -	hwdev->dev.of_node = dev ? dev->of_node : NULL;
> > -	dev_set_drvdata(&hwdev->dev, drvdata);
> > -	dev_set_name(&hwdev->dev, HWMON_ID_FORMAT, id);
> > -	err = device_register(&hwdev->dev);
> > +	hdev->class = &hwmon_class;
> > +	hdev->parent = dev;
> > +	hdev->of_node = dev ? dev->of_node : NULL;
> > +	hwdev->chip = chip;
> > +	dev_set_drvdata(hdev, drvdata);
> > +	dev_set_name(hdev, HWMON_ID_FORMAT, id);
> > +	err = device_register(hdev);
> >  	if (err)
> > -		goto free;
> > +		goto free_hwmon;
> > +
> > +	if (chip && chip->ops->is_visible && chip->ops->read &&
> > +	    chip->info[0]->type == hwmon_chip &&
> > +	    (chip->info[0]->config[0] & HWMON_C_REGISTER_TZ)) {
> > +		const struct hwmon_channel_info **info = chip->info;
> > +
> > +		for (i = 1; info[i]; i++) {
> > +			if (info[i]->type != hwmon_temp)
> > +				continue;
> > +
> > +			for (j = 0; info[i]->config[j]; j++) {
> > +				if (!chip->ops->is_visible(drvdata, hwmon_temp,
> > +							   hwmon_temp_input, j))
> > +					continue;
> > +				if (info[i]->config[j] & HWMON_T_INPUT)
> > +					hwmon_thermal_add_sensor(dev, hwdev, j);
> > +			}
> > +		}
> > +	}
> >  
> > -	return &hwdev->dev;
> > +	return hdev;
> >  
> > -free:
> > +free_hwmon:
> >  	kfree(hwdev);
> >  ida_remove:
> >  	ida_simple_remove(&hwmon_ida, id);
> >  	return ERR_PTR(err);
> >  }
> > +
> > +/**
> > + * hwmon_device_register_with_groups - register w/ hwmon
> > + * @dev: the parent device
> > + * @name: hwmon name attribute
> > + * @drvdata: driver data to attach to created device
> > + * @groups: List of attribute groups to create
> > + *
> > + * hwmon_device_unregister() must be called when the device is no
> > + * longer needed.
> > + *
> > + * Returns the pointer to the new device.
> > + */
> > +struct device *
> > +hwmon_device_register_with_groups(struct device *dev, const char *name,
> > +				  void *drvdata,
> > +				  const struct attribute_group **groups)
> > +{
> > +	return __hwmon_device_register(dev, name, drvdata, NULL, groups);
> > +}
> >  EXPORT_SYMBOL_GPL(hwmon_device_register_with_groups);
> >  
> >  /**
> > + * hwmon_device_register_with_info - register w/ hwmon
> > + * @dev: the parent device
> > + * @name: hwmon name attribute
> > + * @drvdata: driver data to attach to created device
> > + * @info: Pointer to hwmon chip information
> > + * @groups - pointer to list of driver specific attribute groups
> 
> I don't find this clear. "driver specific" doesn't really tell me what
> it is. My first reaction when reviewing the changes from an API
> perspective was "the attributes would be generated from the
> hwmon_chip_info, so why are we still passing them as a parameter?" Now I
> seem to understand that "groups" here is meant for extra attributes
> which aren't part of standard sysfs interface. This would be NULL for
> most drivers, right?
> 
Correct.

> To clear up the confusion, what about renaming this parameter to
> "extra_groups"? And maybe rewording "driver specific" to "non-standard"?
> 
No problem with that.

> As a side note I am wondering if it would be reasonable to limit it to a
> single group, instead of a NULL-terminated array of groups. This would
> make the code a little more efficient.
> 
The underlying code is all the same; hwmon_device_register_with_groups()
also calls __hwmon_device_register(). I would prefer to keep the code as
common as possible.

> > + *
> > + * hwmon_device_unregister() must be called when the device is no
> > + * longer needed.
> > + *
> > + * Returns the pointer to the new device.
> > + */
> > +struct device *
> > +hwmon_device_register_with_info(struct device *dev, const char *name,
> > +				void *drvdata,
> > +				const struct hwmon_chip_info *chip,
> > +				const struct attribute_group **groups)
> > +{
> > +	if (chip && (!chip->ops || !chip->info))
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	return __hwmon_device_register(dev, name, drvdata, chip, groups);
> > +}
> > +EXPORT_SYMBOL_GPL(hwmon_device_register_with_info);
> > +
> > +/**
> >   * hwmon_device_register - register w/ hwmon
> >   * @dev: the device to register
> >   *
> > @@ -211,6 +600,48 @@ error:
> >  }
> >  EXPORT_SYMBOL_GPL(devm_hwmon_device_register_with_groups);
> >  
> > +/**
> > + * devm_hwmon_device_register_with_info - register w/ hwmon
> > + * @dev: the parent device
> > + * @name: hwmon name attribute
> > + * @drvdata: driver data to attach to created device
> > + * @info: Pointer to hwmon chip information
> > + * @groups - pointer to list of driver specific attribute groups
> > + *
> > + * Returns the pointer to the new device. The new device is automatically
> > + * unregistered with the parent device.
> > + */
> > +struct device *
> > +devm_hwmon_device_register_with_info(struct device *dev, const char *name,
> > +				     void *drvdata,
> > +				     const struct hwmon_chip_info *chip,
> > +				     const struct attribute_group **groups)
> > +{
> > +	struct device **ptr, *hwdev;
> > +
> > +	if (!dev)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	ptr = devres_alloc(devm_hwmon_release, sizeof(*ptr), GFP_KERNEL);
> > +	if (!ptr)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	hwdev = hwmon_device_register_with_info(dev, name, drvdata, chip,
> > +						groups);
> > +	if (IS_ERR(hwdev))
> > +		goto error;
> > +
> > +	*ptr = hwdev;
> > +	devres_add(dev, ptr);
> > +
> > +	return hwdev;
> > +
> > +error:
> > +	devres_free(ptr);
> > +	return hwdev;
> > +}
> > +EXPORT_SYMBOL_GPL(devm_hwmon_device_register_with_info);
> > +
> >  static int devm_hwmon_match(struct device *dev, void *res, void *data)
> >  {
> >  	struct device **hwdev = res;
> > diff --git a/include/linux/hwmon.h b/include/linux/hwmon.h
> > index 09354f6c1d63..52e56d71d742 100644
> > --- a/include/linux/hwmon.h
> > +++ b/include/linux/hwmon.h
> > @@ -14,9 +14,147 @@
> >  #ifndef _HWMON_H_
> >  #define _HWMON_H_
> >  
> > +#include <linux/bitops.h>
> > +
> >  struct device;
> >  struct attribute_group;
> >  
> > +enum hwmon_sensor_types {
> > +	hwmon_chip,
> > +	hwmon_temp,
> > +	hwmon_in,
> > +	hwmon_curr,
> > +	hwmon_power,
> > +	hwmon_energy,
> > +};
> > +
> > +enum hwmon_chip_attributes {
> > +	hwmon_chip_temp_reset_history,
> > +	hwmon_chip_register_tz,
> > +	hwmon_chip_update_interval,
> > +	hwmon_chip_alarms,
> > +};
> > +
> > +#define HWMON_C_TEMP_RESET_HISTORY	BIT(hwmon_chip_temp_reset_history)
> > +#define HWMON_C_IN_RESET_HISTORY	BIT(hwmon_chip_in_reset_history)
> 
> Ideally this one should go in next patch ("Add voltage attribute support
> to new API".)
> 
> > +#define HWMON_C_REGISTER_TZ		BIT(hwmon_chip_register_tz)
> > +#define HWMON_C_UPDATE_INTERVAL		BIT(hwmon_chip_update_interval)
> > +#define HWMON_C_ALARMS			BIT(hwmon_chip_alarms)
> > +
> > +enum hwmon_temp_attributes {
> > +	hwmon_temp_input = 0,
> > +	hwmon_temp_type,
> > +	hwmon_temp_lcrit,
> > +	hwmon_temp_lcrit_hyst,
> > +	hwmon_temp_min,
> > +	hwmon_temp_min_hyst,
> > +	hwmon_temp_max,
> > +	hwmon_temp_max_hyst,
> > +	hwmon_temp_crit,
> > +	hwmon_temp_crit_hyst,
> > +	hwmon_temp_emergency,
> > +	hwmon_temp_emergency_hyst,
> > +	hwmon_temp_alarm,
> > +	hwmon_temp_lcrit_alarm,
> > +	hwmon_temp_min_alarm,
> > +	hwmon_temp_max_alarm,
> > +	hwmon_temp_crit_alarm,
> > +	hwmon_temp_emergency_alarm,
> > +	hwmon_temp_fault,
> > +	hwmon_temp_offset,
> > +	hwmon_temp_label,
> > +	hwmon_temp_lowest,
> > +	hwmon_temp_highest,
> > +	hwmon_temp_reset_history,
> > +};
> > +
> > +#define HWMON_T_INPUT		BIT(hwmon_temp_input)
> > +#define HWMON_T_TYPE		BIT(hwmon_temp_type)
> > +#define HWMON_T_LCRIT		BIT(hwmon_temp_lcrit)
> > +#define HWMON_T_LCRIT_HYST	BIT(hwmon_temp_lcrit_hyst)
> > +#define HWMON_T_MIN		BIT(hwmon_temp_min)
> > +#define HWMON_T_MIN_HYST	BIT(hwmon_temp_min_hyst)
> > +#define HWMON_T_MAX		BIT(hwmon_temp_max)
> > +#define HWMON_T_MAX_HYST	BIT(hwmon_temp_max_hyst)
> > +#define HWMON_T_CRIT		BIT(hwmon_temp_crit)
> > +#define HWMON_T_CRIT_HYST	BIT(hwmon_temp_crit_hyst)
> > +#define HWMON_T_EMERGENCY	BIT(hwmon_temp_emergency)
> > +#define HWMON_T_EMERGENCY_HYST	BIT(hwmon_temp_emergency_hyst)
> > +#define HWMON_T_MIN_ALARM	BIT(hwmon_temp_min_alarm)
> > +#define HWMON_T_MAX_ALARM	BIT(hwmon_temp_max_alarm)
> > +#define HWMON_T_CRIT_ALARM	BIT(hwmon_temp_crit_alarm)
> > +#define HWMON_T_EMERGENCY_ALARM	BIT(hwmon_temp_emergency_alarm)
> > +#define HWMON_T_FAULT		BIT(hwmon_temp_fault)
> > +#define HWMON_T_OFFSET		BIT(hwmon_temp_offset)
> > +#define HWMON_T_LABEL		BIT(hwmon_temp_label)
> > +#define HWMON_T_LOWEST		BIT(hwmon_temp_lowest)
> > +#define HWMON_T_HIGHEST		BIT(hwmon_temp_highest)
> > +#define HWMON_T_RESET_HISTORY	BIT(hwmon_temp_reset_history)
> > +
> > +/**
> > + * struct hwmon_ops - hwmon device operations
> > + * @is_visible: Callback to return attribute visibility. Mandatory.
> > + *		Parameters are:
> > + *		@const void *drvdata:
> > + *			Pointer to driver-private data structure passed
> > + *			as argument to hwmon_device_register_with_info().
> > + *		@type:	Sensor type
> > + *		@attr:	Sensor attribute
> > + *		@channel:
> > + *			Channel number
> > + *		The function returns the file permissions.
> > + *		If the return value is 0, no attribute will be created.
> > + * @read:       Read callback. Optional. If not provided, attributes
> > + *		will not be readable.
> > + *		Parameters are:
> > + *		@dev:	Pointer to hardware monitoring device
> > + *		@type:	Sensor type
> > + *		@attr:	Sensor attribute
> > + *		@channel:
> > + *			Channel number
> > + *		@val:	Pointer to returned value
> > + *		The function returns 0 on success or a negative error number.
> > + * @write:	Write callback. Optional. If not provided, attributes
> > + *		will not be writable.
> > + *		Parameters are:
> > + *		@dev:	Pointer to hardware monitoring device
> > + *		@type:	Sensor type
> > + *		@attr:	Sensor attribute
> > + *		@channel:
> > + *			Channel number
> > + *		@val:	Value to write
> > + *		The function returns 0 on success or a negative error number.
> > + */
> > +struct hwmon_ops {
> > +	umode_t (*is_visible)(const void *drvdata, enum hwmon_sensor_types type,
> > +			      u32 attr, int channel);
> > +	int (*read)(struct device *dev, enum hwmon_sensor_types type,
> > +		    u32 attr, int channel, long *val);
> > +	int (*write)(struct device *dev, enum hwmon_sensor_types type,
> > +		     u32 attr, int channel, long val);
> > +};
> > +
> > +/**
> > + * Channel information
> > + * @type:	Channel type.
> > + * @config:	Pointer to NULL-terminated list of channel parameters.
> > + *		Use for per-channel attributes.
> > + */
> > +struct hwmon_channel_info {
> > +	enum hwmon_sensor_types type;
> > +	const u32 *config;
> > +};
> > +
> > +/**
> > + * Chip configuration
> > + * @ops:	Pointer to hwmon operations.
> > + * @info:	Null-terminated list of channel information.
> > + */
> > +struct hwmon_chip_info {
> > +	const struct hwmon_ops *ops;
> > +	const struct hwmon_channel_info **info;
> > +};
> > +
> >  struct device *hwmon_device_register(struct device *dev);
> >  struct device *
> >  hwmon_device_register_with_groups(struct device *dev, const char *name,
> > @@ -26,6 +164,16 @@ struct device *
> >  devm_hwmon_device_register_with_groups(struct device *dev, const char *name,
> >  				       void *drvdata,
> >  				       const struct attribute_group **groups);
> > +struct device *
> > +hwmon_device_register_with_info(struct device *dev,
> > +				const char *name, void *drvdata,
> > +				const struct hwmon_chip_info *info,
> > +				const struct attribute_group **groups);
> > +struct device *
> > +devm_hwmon_device_register_with_info(struct device *dev,
> > +				     const char *name, void *drvdata,
> > +				     const struct hwmon_chip_info *info,
> > +				     const struct attribute_group **groups);
> >  
> >  void hwmon_device_unregister(struct device *dev);
> >  void devm_hwmon_device_unregister(struct device *dev);
> 
> This is adding a 4th and 5th way to register a hwmon device. Starts
> being a bit messy... Do you have any plans to get rid of some of the
> other functions to make things more consistent and efficient?
> 
Would be nice, but then someone would have to spend the time cleaning
up the old drivers to replace the old API, and for the most part we would
not be able to test the result. Are you sure that is worth the risk ?

Thanks,
Guenter

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