Commit 8f4fd97d authored by Guenter Roeck's avatar Guenter Roeck
Browse files

hwmon: (amc6821) Make reading and writing fan speed limits consistent 



The default value of the maximum fan speed limit register is 0,
essentially translating to an unlimited fan speed. When reading
the limit, a value of 0 is reported in this case. However, writing
a value of 0 results in writing a value of 0xffff into the register,
which is inconsistent.

To solve the problem, permit writing a limit of 0 for the maximim fan
speed, effectively translating to "no limit". Write 0 into the register
if a limit value of 0 is written. Otherwise limit the range to
<1..6000000> and write 1..0xffff into the register. This ensures that
reading and writing from and to a limit register return the same value
while at the same time not changing reported values when reading the
speed or limits.

While at it, restrict fan limit writes to non-negative numbers; writing
a negative limit does not make sense and should be reported instead of
being corrected.

Reviewed-by: default avatarQuentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent af4d04b8

drivers/hwmon/amc6821.c

+9 −4
Original line number Diff line number Diff line
@@ -616,15 +616,20 @@ static ssize_t fan_store(struct device *dev, struct device_attribute *attr, 
{

	struct amc6821_data *data = dev_get_drvdata(dev);

	struct i2c_client *client = data->client;

	long val;

	unsigned long val;

	int ix = to_sensor_dev_attr(attr)->index;

	int ret = kstrtol(buf, 10, &val);

	int ret = kstrtoul(buf, 10, &val);

	if (ret)

		return ret;

	val = 1 > val ? 0xFFFF : 6000000/val;



	/* The minimum fan speed must not be unlimited (0) */

	if (ix == IDX_FAN1_MIN && !val)

		return -EINVAL;



	val = val > 0 ? 6000000 / clamp_val(val, 1, 6000000) : 0;



	mutex_lock(&data->update_lock);

	data->fan[ix] = (u16) clamp_val(val, 1, 0xFFFF);

	data->fan[ix] = clamp_val(val, 0, 0xFFFF);

	if (i2c_smbus_write_byte_data(client, fan_reg_low[ix],

			data->fan[ix] & 0xFF)) {

		dev_err(&client->dev, "Register write error, aborting.\n");