On 7/1/24 04:05, Quentin Schulz wrote:
Hi Guenter,
On 6/28/24 5:13 PM, Guenter Roeck wrote:
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.
> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
drivers/hwmon/amc6821.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
index 3c614a0bd192..e37257ae1a6b 100644
--- a/drivers/hwmon/amc6821.c
+++ b/drivers/hwmon/amc6821.c
@@ -601,7 +601,7 @@ static ssize_t fan_show(struct device *dev, struct device_attribute *devattr,
struct amc6821_data *data = amc6821_update_device(dev);
int ix = to_sensor_dev_attr(devattr)->index;
if (0 == data->fan[ix])
- return sprintf(buf, "0");
+ return sprintf(buf, "6000000");
return sprintf(buf, "%d\n", (int)(6000000 / data->fan[ix]));
}
@@ -625,10 +625,10 @@ static ssize_t fan_store(struct device *dev, struct device_attribute *attr,
int ret = kstrtol(buf, 10, &val);
if (ret)
return ret;
- val = 1 > val ? 0xFFFF : 6000000/val;
+ val = val < 1 ? 0xFFFF : 6000000 / val;
mutex_lock(&data->update_lock);
- data->fan[ix] = (u16) clamp_val(val, 1, 0xFFFF);
+ data->fan[ix] = (u16)clamp_val(val, 0, 0xFFFF);
This is an unrelated change I believe and I would therefore have this in its own commit with proper documentation in the commit log. Indeed:
1- Change in fan_show handles the default 0x0 register value (which can only currently be achieved via the default value of the registers)
2- Allow (re-)setting unlimited fan speed by allowing the user to pass 6000001+ instead of clamping it to 6000000 RPM.
Both changes are related.
The whole point of this commit is to report and permit consistent values when
the register value is 0. But you do have a point - reading it after my changes
returns 6000000, but writing the same value sets the register to 1. So I think
the proper change would be to display 6000001 as speed if the register value is
0, and provide a more detailed explanation. Would that address your concerns ?
Thanks,
Guenter
