Re: [PATCH v3 2/2] ACPI: fan: Add hwmon support

From: Armin Wolf
Date: Fri Apr 12 2024 - 16:28:39 EST

Am 12.04.24 um 18:41 schrieb Guenter Roeck:

On Fri, Apr 12, 2024 at 06:08:57PM +0200, Armin Wolf wrote:
Currently, the driver does only support a custom sysfs
to allow userspace to read the fan speed.
Add support for the standard hwmon interface so users
can read the fan speed with standard tools like "sensors".

Compile-tested only.

Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
---
Changes since v2:
- add support for fanX_target and power attrs

Changes since v1:
- fix undefined reference error
- fix fan speed validation
- coding style fixes
- clarify that the changes are compile-tested only
- add hwmon maintainers to cc list

The changes will be tested by Mikael Lund Jepsen from Danelec and
should be merged only after those tests.
---
drivers/acpi/Makefile | 1 +
drivers/acpi/fan.h | 9 +++
drivers/acpi/fan_core.c | 4 ++
drivers/acpi/fan_hwmon.c | 148 +++++++++++++++++++++++++++++++++++++++
4 files changed, 162 insertions(+)
create mode 100644 drivers/acpi/fan_hwmon.c

diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 39ea5cfa8326..61ca4afe83dc 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -77,6 +77,7 @@ obj-$(CONFIG_ACPI_TINY_POWER_BUTTON) += tiny-power-button.o
obj-$(CONFIG_ACPI_FAN) += fan.o
fan-objs := fan_core.o
fan-objs += fan_attr.o
+fan-$(CONFIG_HWMON) += fan_hwmon.o

obj-$(CONFIG_ACPI_VIDEO) += video.o
obj-$(CONFIG_ACPI_TAD) += acpi_tad.o
diff --git a/drivers/acpi/fan.h b/drivers/acpi/fan.h
index f89d19c922dc..db25a3898af7 100644
--- a/drivers/acpi/fan.h
+++ b/drivers/acpi/fan.h
@@ -10,6 +10,8 @@
#ifndef _ACPI_FAN_H_
#define _ACPI_FAN_H_

+#include <linux/kconfig.h>
+
#define ACPI_FAN_DEVICE_IDS \
{"INT3404", }, /* Fan */ \
{"INTC1044", }, /* Fan for Tiger Lake generation */ \
@@ -57,4 +59,11 @@ struct acpi_fan {
int acpi_fan_get_fst(struct acpi_device *device, struct acpi_fan_fst *fst);
int acpi_fan_create_attributes(struct acpi_device *device);
void acpi_fan_delete_attributes(struct acpi_device *device);
+
+#if IS_REACHABLE(CONFIG_HWMON)
+int devm_acpi_fan_create_hwmon(struct acpi_device *device);
+#else
+static inline int devm_acpi_fan_create_hwmon(struct acpi_device *device) { return 0; };
+#endif
+
#endif
diff --git a/drivers/acpi/fan_core.c b/drivers/acpi/fan_core.c
index ff72e4ef8738..7cea4495f19b 100644
--- a/drivers/acpi/fan_core.c
+++ b/drivers/acpi/fan_core.c
@@ -336,6 +336,10 @@ static int acpi_fan_probe(struct platform_device *pdev)
if (result)
return result;

+ result = devm_acpi_fan_create_hwmon(device);
+ if (result)
+ return result;
+
result = acpi_fan_create_attributes(device);
if (result)
return result;
diff --git a/drivers/acpi/fan_hwmon.c b/drivers/acpi/fan_hwmon.c
new file mode 100644
index 000000000000..57216ba872db
--- /dev/null
+++ b/drivers/acpi/fan_hwmon.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * fan_hwmon.c - hwmon interface for the ACPI Fan driver
+ *
+ * Copyright (C) 2024 Armin Wolf <W_Armin@xxxxxx>
+ */
+
+#include <linux/acpi.h>
+#include <linux/hwmon.h>
+#include <linux/limits.h>
+#include <linux/units.h>
+
+#include "fan.h"
+
+/* Returned when the ACPI fan does not support speed reporting */
+#define FAN_SPEED_UNAVAILABLE 0xffffffff
+#define FAN_POWER_UNAVAILABLE 0xffffffff
+
+static struct acpi_fan_fps *acpi_fan_get_current_fps(struct acpi_fan *fan, u64 control)
+{
+ int i;
+
+ for (i = 0; i < fan->fps_count; i++) {
+ if (fan->fps[i].control == control)
+ return &fan->fps[i];
+ }
+
+ return NULL;
+}
+
+static umode_t acpi_fan_is_visible(const void *drvdata, enum hwmon_sensor_types type, u32 attr,
+ int channel)
+{
+ return 0444;
+}
+
+static int acpi_fan_read(struct device *dev, enum hwmon_sensor_types type, u32 attr, int channel,
+ long *val)
+{
+ struct acpi_device *adev = dev_get_drvdata(dev);
+ struct acpi_fan *fan = acpi_driver_data(adev);
+ struct acpi_fan_fps *fps;
+ struct acpi_fan_fst fst;
+ int ret;
+
+ ret = acpi_fan_get_fst(adev, &fst);
+ if (ret < 0)
+ return ret;
+
+ switch (type) {
+ case hwmon_fan:
+ switch (attr) {
+ case hwmon_fan_input:
+ if (fst.speed == FAN_SPEED_UNAVAILABLE)
+ return -ENODATA;
+
+ if (fst.speed > LONG_MAX)
+ return -EOVERFLOW;
+
+ *val = fst.speed;
+ return 0;
+ case hwmon_fan_target:
+ fps = acpi_fan_get_current_fps(fan, fst.control);
+ if (!fps)
+ return -ENODATA;
+
+ *val = fps->speed;
+ return 0;
+ case hwmon_fan_fault:
+ *val = (fst.speed == FAN_SPEED_UNAVAILABLE);
Is it documented that this is indeed a fault (broken fan) ?

Hi,

it actually means that the fan does not support speed reporting.

+ return 0;
+ default:
+ break;
+ }
+ break;
+ case hwmon_power:
+ fps = acpi_fan_get_current_fps(fan, fst.control);
+ if (!fps)
+ return -ENODATA;
+
+ switch (attr) {
+ case hwmon_power_input:
+ if (fps->power == FAN_POWER_UNAVAILABLE)
+ return -ENODATA;
+
+ if (fps->power > LONG_MAX / MICROWATT_PER_MILLIWATT)
+ return -EOVERFLOW;
+
+ *val = fps->power * MICROWATT_PER_MILLIWATT;
+ return 0;
+ case hwmon_power_fault:
+ *val = (fps->power == FAN_POWER_UNAVAILABLE);
Is it documented that this is indeed a power supply failure ?
What if the value is simply not reported ? "UNAVAILABLE" is not
commonly associated with a "fault".

Guenter

FAN_POWER_UNAVAILABLE signals that the power value is not supported.
Would it be more suitable to drop the fault attributes and just return -ENODATA in such a case?

Thanks,
Armin Wolf

+ return 0;
+ default:
+ break;
+ }
+ break;
+ default:
+ break;
+ }
+
+ return -EOPNOTSUPP;
+}
+
+static const struct hwmon_ops acpi_fan_ops = {
+ .is_visible = acpi_fan_is_visible,
+ .read = acpi_fan_read,
+};
+
+static const struct hwmon_channel_info * const acpi_fan_info[] = {
+ HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_TARGET | HWMON_F_FAULT),
+ HWMON_CHANNEL_INFO(power, HWMON_P_INPUT | HWMON_P_FAULT),
+ NULL
+};
+
+static const struct hwmon_chip_info acpi_fan_chip_info = {
+ .ops = &acpi_fan_ops,
+ .info = acpi_fan_info,
+};
+
+static const struct hwmon_channel_info * const acpi_fan_fine_grain_info[] = {
+ HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_FAULT),
+ NULL
+};
+
+static const struct hwmon_chip_info acpi_fan_fine_grain_chip_info = {
+ .ops = &acpi_fan_ops,
+ .info = acpi_fan_fine_grain_info,
+};
+
+int devm_acpi_fan_create_hwmon(struct acpi_device *device)
+{
+ struct acpi_fan *fan = acpi_driver_data(device);
+ const struct hwmon_chip_info *info;
+ struct device *hdev;
+
+ /* When in fine grain control mode, not every fan control value
+ * has an associated fan performance state.
+ */
+ if (fan->fif.fine_grain_ctrl)
+ info = &acpi_fan_fine_grain_chip_info;
+ else
+ info = &acpi_fan_chip_info;
+
+ hdev = devm_hwmon_device_register_with_info(&device->dev, "acpi_fan", device, info, NULL);
+
+ return PTR_ERR_OR_ZERO(hdev);
+}
--
2.39.2