[PATCH 1/2] hwmon: Add pwmX_fan_channel attribute

[Armin Wolf]

Until now, userspace software needs to guess which
PWM channel is associated with which fan channel by
probing each PWM output and watch for fan speed changes.
This proccess is error-prone and unreliable.

Some hwmon chips, especially firmware-based ones, already
know which PWM output is associated with which fan channel.

Allow such chips to export this knowledge to userspace.

Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
---
 Documentation/ABI/testing/sysfs-class-hwmon | 8 ++++++++
 Documentation/hwmon/sysfs-interface.rst     | 3 +++
 drivers/hwmon/hwmon.c                       | 1 +
 include/linux/hwmon.h                       | 2 ++
 4 files changed, 14 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-hwmon b/Documentation/ABI/testing/sysfs-class-hwmon
index 7271781a23b2..f3d653bcf736 100644
--- a/Documentation/ABI/testing/sysfs-class-hwmon
+++ b/Documentation/ABI/testing/sysfs-class-hwmon
@@ -315,6 +315,14 @@ Description:

 		RW

+What:		/sys/class/hwmon/hwmonX/pwmY_fan_channel
+Description:
+		Select which fan channel is controlled by this PWM output.
+
+		Valid fan channel/PWM output combinations are chip-dependent.
+
+		RW
+
 What:		/sys/class/hwmon/hwmonX/pwmY_auto_channels_temp
 Description:
 		Select which temperature channels affect this PWM output in
diff --git a/Documentation/hwmon/sysfs-interface.rst b/Documentation/hwmon/sysfs-interface.rst
index 209626fb2405..17fcec03d3c5 100644
--- a/Documentation/hwmon/sysfs-interface.rst
+++ b/Documentation/hwmon/sysfs-interface.rst
@@ -209,6 +209,9 @@ PWM
 `pwm[1-*]_freq`
 		Base PWM frequency in Hz.

+`pwm[1-*]_fan_channel`
+                Select which fan channel is controlled by this PWM output.
+
 `pwm[1-*]_auto_channels_temp`
 		Select which temperature channels affect this PWM output in
 		auto mode.
diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
index 2e2cd79d89eb..8c2d7574c461 100644
--- a/drivers/hwmon/hwmon.c
+++ b/drivers/hwmon/hwmon.c
@@ -604,6 +604,7 @@ static const char * const hwmon_pwm_attr_templates[] = {
 	[hwmon_pwm_enable] = "pwm%d_enable",
 	[hwmon_pwm_mode] = "pwm%d_mode",
 	[hwmon_pwm_freq] = "pwm%d_freq",
+	[hwmon_pwm_fan_channel] = "pwm%d_fan_channel",
 	[hwmon_pwm_auto_channels_temp] = "pwm%d_auto_channels_temp",
 };

diff --git a/include/linux/hwmon.h b/include/linux/hwmon.h
index 14325f93c6b2..9d40cc1e520f 100644
--- a/include/linux/hwmon.h
+++ b/include/linux/hwmon.h
@@ -332,6 +332,7 @@ enum hwmon_pwm_attributes {
 	hwmon_pwm_enable,
 	hwmon_pwm_mode,
 	hwmon_pwm_freq,
+	hwmon_pwm_fan_channel,
 	hwmon_pwm_auto_channels_temp,
 };

@@ -339,6 +340,7 @@ enum hwmon_pwm_attributes {
 #define HWMON_PWM_ENABLE		BIT(hwmon_pwm_enable)
 #define HWMON_PWM_MODE			BIT(hwmon_pwm_mode)
 #define HWMON_PWM_FREQ			BIT(hwmon_pwm_freq)
+#define HWMON_PWM_FAN_CHANNEL		BIT(hwmon_pwm_fan_channel)
 #define HWMON_PWM_AUTO_CHANNELS_TEMP	BIT(hwmon_pwm_auto_channels_temp)

 enum hwmon_intrusion_attributes {
--
2.30.2