[PATCH 1/2] hwmon: (core) Add hwmon_mode structure and mode sysfs node

[Nicolin Chen]

There are a few hwmon sensors support different operating modes,
for example, one-shot and continuous modes. So it's probably not
a bad idea to abstract a mode sysfs node as a common feature in
the hwmon core.

Right beside the hwmon device name, this patch adds a new sysfs
attribute named "mode" and "available_modes" for user to check
and configure the operating mode. For hwmon device drivers that
implemented the _with_info API, the change also adds an optional
hwmon_mode structure in hwmon_chip_info structure so that those
drivers can pass mode related information.

Signed-off-by: Nicolin Chen <nicoleotsuka@xxxxxxxxx>
---
 Documentation/hwmon/sysfs-interface | 15 +++++
 drivers/hwmon/hwmon.c               | 87 ++++++++++++++++++++++++++---
 include/linux/hwmon.h               | 24 ++++++++
 3 files changed, 119 insertions(+), 7 deletions(-)

diff --git a/Documentation/hwmon/sysfs-interface b/Documentation/hwmon/sysfs-interface
index 2b9e1005d88b..48d6ca6b9bd4 100644
--- a/Documentation/hwmon/sysfs-interface
+++ b/Documentation/hwmon/sysfs-interface
@@ -92,6 +92,21 @@ name		The chip name.
 		I2C devices get this attribute created automatically.
 		RO
 
+available_modes The available operating modes of the chip.
+		This should be short, lowercase string, not containing
+		whitespace, or the wildcard character '*'.
+		This attribute shows all the available of the operating modes,
+		for example, "power-down" "one-shot" and "continuous".
+		RO
+
+mode		The current operating mode of the chip.
+		This should be short, lowercase string, not containing
+		whitespace, or the wildcard character '*'.
+		This attribute shows the current operating mode of the chip.
+		Writing a valid string from the list of available_modes will
+		configure the chip to the corresponding operating mode.
+		RW
+
 update_interval	The interval at which the chip will update readings.
 		Unit: millisecond
 		RW
diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
index 975c95169884..5a33b616284b 100644
--- a/drivers/hwmon/hwmon.c
+++ b/drivers/hwmon/hwmon.c
@@ -72,25 +72,88 @@ name_show(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR_RO(name);
 
+static ssize_t available_modes_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct hwmon_device *hwdev = to_hwmon_device(dev);
+	const struct hwmon_chip_info *chip = hwdev->chip;
+	const struct hwmon_mode *mode = chip->mode;
+	int i;
+
+	for (i = 0; i < mode->list_size; i++)
+		snprintf(buf, PAGE_SIZE, "%s%s ", buf, mode->names[i]);
+
+	return snprintf(buf, PAGE_SIZE, "%s\n", buf);
+}
+static DEVICE_ATTR_RO(available_modes);
+
+static ssize_t mode_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct hwmon_device *hwdev = to_hwmon_device(dev);
+	const struct hwmon_chip_info *chip = hwdev->chip;
+	const struct hwmon_mode *mode = chip->mode;
+	unsigned int index;
+	int ret;
+
+	ret = mode->get_index(dev, &index);
+	if (ret)
+		return ret;
+
+	return snprintf(buf, PAGE_SIZE, "%s\n", mode->names[index]);
+}
+
+static ssize_t mode_store(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	struct hwmon_device *hwdev = to_hwmon_device(dev);
+	const struct hwmon_chip_info *chip = hwdev->chip;
+	const struct hwmon_mode *mode = chip->mode;
+	const char **names = mode->names;
+	unsigned int index;
+	int ret;
+
+	/* Get the corresponding mode index */
+	for (index = 0; index < mode->list_size; index++) {
+		if (!strncmp(buf, names[index], strlen(names[index])))
+			break;
+	}
+
+	if (index >= mode->list_size)
+		return -EINVAL;
+
+	ret = mode->set_index(dev, index);
+	if (ret)
+		return ret;
+
+	return count;
+}
+static DEVICE_ATTR_RW(mode);
+
 static struct attribute *hwmon_dev_attrs[] = {
-	&dev_attr_name.attr,
+	&dev_attr_name.attr,		/* index = 0 */
+	&dev_attr_available_modes.attr,	/* index = 1 */
+	&dev_attr_mode.attr,		/* index = 2 */
 	NULL
 };
 
-static umode_t hwmon_dev_name_is_visible(struct kobject *kobj,
-					 struct attribute *attr, int n)
+static umode_t hwmon_dev_is_visible(struct kobject *kobj,
+				    struct attribute *attr, int n)
 {
 	struct device *dev = container_of(kobj, struct device, kobj);
+	struct hwmon_device *hwdev = to_hwmon_device(dev);
 
-	if (to_hwmon_device(dev)->name == NULL)
-		return 0;
+	if (n == 0 && hwdev->name)
+		return attr->mode;
+	else if (n <= 2 && hwdev->chip->mode)
+		return attr->mode;
 
-	return attr->mode;
+	return 0;
 }
 
 static const struct attribute_group hwmon_dev_attr_group = {
 	.attrs		= hwmon_dev_attrs,
-	.is_visible	= hwmon_dev_name_is_visible,
+	.is_visible	= hwmon_dev_is_visible,
 };
 
 static const struct attribute_group *hwmon_dev_attr_groups[] = {
@@ -591,6 +654,16 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
 		struct attribute **attrs;
 		int ngroups = 2; /* terminating NULL plus &hwdev->groups */
 
+		/* Validate optional hwmon_mode */
+		if (chip->mode) {
+			/* Check mandatory properties */
+			if (!chip->mode->names || !chip->mode->list_size ||
+			    !chip->mode->get_index || !chip->mode->set_index) {
+				err = -EINVAL;
+				goto free_hwmon;
+			}
+		}
+
 		if (groups)
 			for (i = 0; groups[i]; i++)
 				ngroups++;
diff --git a/include/linux/hwmon.h b/include/linux/hwmon.h
index 99e0c1b0b5fb..06c1940ca98b 100644
--- a/include/linux/hwmon.h
+++ b/include/linux/hwmon.h
@@ -365,14 +365,38 @@ struct hwmon_channel_info {
 	const u32 *config;
 };
 
+/**
+ * Chip operating mode information
+ * @names:	A list of available operating mode names.
+ * @list_size:	The total number of available operating mode names.
+ * @get_index:	Callback to get current operating mode index. Mandatory.
+ *		Parameters are:
+ *		@dev:	Pointer to hardware monitoring device
+ *		@index:	Pointer to returned mode index
+ *		The function returns 0 on success or a negative error number.
+ * @set_index:	Callback to set operating mode using the index. Mandatory.
+ *		Parameters are:
+ *		@dev:	Pointer to hardware monitoring device
+ *		@index:	Mode index in the mode list
+ *		The function returns 0 on success or a negative error number.
+ */
+struct hwmon_mode {
+	const char **names;
+	unsigned int list_size;
+	int (*get_index)(struct device *dev, unsigned int *index);
+	int (*set_index)(struct device *dev, unsigned int index);
+};
+
 /**
  * Chip configuration
  * @ops:	Pointer to hwmon operations.
  * @info:	Null-terminated list of channel information.
+ * @mode:	Pointer to hwmon operating mode (optional).
  */
 struct hwmon_chip_info {
 	const struct hwmon_ops *ops;
 	const struct hwmon_channel_info **info;
+	const struct hwmon_mode *mode;
 };
 
 /* hwmon_device_register() is deprecated */
-- 
2.17.1