On Friday 28 May 2021 22:37:06 Armin Wolf wrote: > Am 28.05.21 um 19:53 schrieb Pali Rohár: > > On Friday 28 May 2021 19:37:16 W_Armin@xxxxxx wrote: > > > From: Armin Wolf <W_Armin@xxxxxx> > > > > > > pwm1_enable is now readable too. > > Hello! pwm1_enable cannot be readable. It is write-only node. See also: > > https://lore.kernel.org/linux-hwmon/201605221717.26604@pali/ > > > Hello, > > in Documentation/hwmon/sysfs-interface, pwmX_enable is marked as RW, and the document also states that > "Read/write values may be read-only for some chips, depending on the hardware implementation", so i > thought that pwm1_enable being WO is a violation of that rule. I know that hwmon sysfs are rw but if driver cannot provide correct read value then it is better to do not report it. > Also i belive the i8kutils are not calling SMM anymore, so can we just leave a note saying something like > "this value is cached and is not correct when using certain userspace tools which disable/enable BIOS fan control"? Well, maybe state changed in time (it is 5 years since that email) but there are still more older versions of i8k userspace tools and some of them used to issue SMM calls. Personally, I have used them (prior introducing kernel support) and I can expect that other people who wrote other scripts may have them in their inittab (or converted to systemd equivalent). So it is better to not expect that something is not used. Whole SMM stuff is fragile for various reasons... Also another issue is that initial value is unknown. Because we do not know if BIOS fan control is enabled or disabled. I was told that in past BIOS fan control was old Dell laptops was disabled, so if people adds old laptops into whilelist it would mean that we even do not guess state of BIOS fan control status. > > > Signed-off-by: Armin Wolf <W_Armin@xxxxxx> > > > --- > > > Documentation/hwmon/dell-smm-hwmon.rst | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/Documentation/hwmon/dell-smm-hwmon.rst b/Documentation/hwmon/dell-smm-hwmon.rst > > > index 3bf77a5df995..d6fe9b8a2c40 100644 > > > --- a/Documentation/hwmon/dell-smm-hwmon.rst > > > +++ b/Documentation/hwmon/dell-smm-hwmon.rst > > > @@ -35,7 +35,7 @@ Name Perm Description > > > fan[1-3]_input RO Fan speed in RPM. > > > fan[1-3]_label RO Fan label. > > > pwm[1-3] RW Control the fan PWM duty-cycle. > > > -pwm1_enable WO Enable or disable automatic BIOS fan > > > +pwm1_enable RW Enable or disable automatic BIOS fan > > > control (not supported on all laptops, > > > see below for details). > > > temp[1-10]_input RO Temperature reading in milli-degrees > > > -- > > > 2.20.1 > > > >
