On 9/3/21 7:49 AM, Pali Rohár wrote:
On Friday 03 September 2021 16:24:56 W_Armin@xxxxxx wrote:
From: Armin Wolf <W_Armin@xxxxxx>
For allowing tools like i8kutils to query the fan state
without having to rely on the deprecated /proc/i8k interface,
they need to scale the pwm values (0 - 255) back to the
real hardware values (0 - 2/3).
Show fan_max in sysfs to allow for such a scenario.
Guenter, I think that this is general problem and not specific to
dell-smm-hwmon.c driver and i8kutils.
All other hwmon tools should have similar problem. If e.g. GUI tool has
slider for controlling pwm then such tool needs to know number of steps.
Otherwise usage of such slider would be not very user friendly...
Currently in hwmon sysfs API there is not attribute which could export
this kind of information.
What about e.g. introducing 'pwm_steps' attribute which would provide
this information?
It isn't really a problem. The problem is that the tool writers insist
not following the ABI. All they would have to do is to use a scale of 0..255,
read back any written pwm value, and adjust the displayed value based
on the returned value. I do not see why this would be "not user friendly".
An attribute such as pwm_steps would not work because the step size can be
non-linear.
Guenter
Tested on a Dell Latitude C600.
Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
---
drivers/hwmon/dell-smm-hwmon.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index 774c1b0715d9..6d3fd4f0f99d 100644
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -107,7 +107,7 @@ module_param(fan_mult, uint, 0);
MODULE_PARM_DESC(fan_mult, "Factor to multiply fan speed with (default: autodetect)");
static uint fan_max;
-module_param(fan_max, uint, 0);
+module_param(fan_max, uint, 0444);
MODULE_PARM_DESC(fan_max, "Maximum configurable fan speed (default: autodetect)");
struct smm_regs {
@@ -1245,7 +1245,10 @@ static int __init dell_smm_probe(struct platform_device *pdev)
fan_max = conf->fan_max;
}
- data->i8k_fan_max = fan_max ? : I8K_FAN_HIGH; /* Must not be 0 */
+ if (!fan_max) /* Must not be 0*/
+ fan_max = I8K_FAN_HIGH;
+
+ data->i8k_fan_max = fan_max;
data->i8k_pwm_mult = DIV_ROUND_UP(255, data->i8k_fan_max);
fan_control = dmi_first_match(i8k_whitelist_fan_control);
--
2.20.1
