[PATCH 6/6] hwmon: (f75375s) Catch some attempts to write to r/o registers

[Nikolaus Schulz <mail@xxxxxxxxxxxxxx>]

It makes no sense to attempt to manually configure the fan in auto mode,
or set the duty cycle directly in closed loop mode.  The corresponding
registers are then read-only.  If the user tries it nonetheless, error out
with EBUSY instead of silently doing nothing.

Signed-off-by: Nikolaus Schulz <mail@xxxxxxxxxxxxxx>
---
 drivers/hwmon/f75375s.c |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/drivers/hwmon/f75375s.c b/drivers/hwmon/f75375s.c
index 29b11c6..0e7fe3a 100644
--- a/drivers/hwmon/f75375s.c
+++ b/drivers/hwmon/f75375s.c
@@ -281,6 +281,21 @@ static bool duty_mode_enabled(u8 pwm_enable)
 	}
 }
 
+static bool auto_mode_enabled(u8 pwm_enable)
+{
+	switch (pwm_enable) {
+	case 0: /* Manual, duty mode (full speed) */
+	case 1: /* Manual, duty mode */
+	case 3: /* Manual, speed mode */
+		return false;
+	case 2: /* Auto, speed mode */
+	case 4: /* Auto, duty mode */
+		return true;
+	default:
+		BUG();
+	}
+}
+
 static ssize_t set_fan_min(struct device *dev, struct device_attribute *attr,
 		const char *buf, size_t count)
 {
@@ -314,6 +329,11 @@ static ssize_t set_fan_target(struct device *dev, struct device_attribute *attr,
 	if (err < 0)
 		return err;
 
+	if (auto_mode_enabled(data->pwm_enable[nr]))
+		return -EBUSY;
+	if (data->kind == f75387 && duty_mode_enabled(data->pwm_enable[nr]))
+		return -EBUSY;
+
 	mutex_lock(&data->update_lock);
 	data->fan_target[nr] = rpm_to_reg(val);
 	f75375_write16(client, F75375_REG_FAN_EXP(nr), data->fan_target[nr]);
@@ -334,6 +354,10 @@ static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
 	if (err < 0)
 		return err;
 
+	if (auto_mode_enabled(data->pwm_enable[nr]) ||
+			!duty_mode_enabled(data->pwm_enable[nr]))
+		return -EBUSY;
+
 	mutex_lock(&data->update_lock);
 	/* TODO: Improve representation in the register cache for the F75387 */
 	data->pwm[nr] = SENSORS_LIMIT(val, 0, 255);
@@ -819,6 +843,14 @@ static void f75375_init(struct i2c_client *client, struct f75375_data *data,
 	set_pwm_enable_direct(client, 0, f75375s_pdata->pwm_enable[0]);
 	set_pwm_enable_direct(client, 1, f75375s_pdata->pwm_enable[1]);
 	for (nr = 0; nr < 2; nr++) {
+		if (auto_mode_enabled(f75375s_pdata->pwm_enable[nr]) ||
+		   !duty_mode_enabled(f75375s_pdata->pwm_enable[nr])) {
+			dev_err(data->hwmon_dev,
+				"fan %d: cannot set duty cycle in mode %d",
+				nr,
+				f75375s_pdata->pwm_enable[nr]);
+			continue;
+		}
 		data->pwm[nr] = SENSORS_LIMIT(f75375s_pdata->pwm[nr], 0, 255);
 		if (data->kind == f75387)
 			f75375_write16(client, F75375_REG_FAN_EXP(nr),
-- 
1.7.9.1


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