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

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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: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Guenter Roeck 2024-06-26 17:46:04 -07:00
parent af4d04b8ce
commit 8f4fd97df2
1 changed files with 9 additions and 4 deletions
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13
drivers/hwmon/amc6821.c
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@ -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");