On Fri, Nov 22, 2019 at 11:15:19AM +0100, Giovanni Mascellani wrote: > Part of the documentation is taken from the README of the userspace > utils (https://github.com/vitorafsr/i8kutils). The license is GPL-2+ > and the author Massimo Dal Zotto is already credited as author of > the module. Therefore there should be no copyright problem. > > I also added a paragraph with specific information on the experimental > support for automatic BIOS fan control. > > Signed-off-by: Giovanni Mascellani <gio@xxxxxxxxxx> Applied. I fixed one of the documentation build warnings, but there is one more which I don't understand and thus left alone. > --- > Documentation/hwmon/dell-smm-hwmon.rst | 164 +++++++++++++++++++++++++ > Documentation/hwmon/index.rst | 1 + > 2 files changed, 165 insertions(+) > create mode 100644 Documentation/hwmon/dell-smm-hwmon.rst > > diff --git a/Documentation/hwmon/dell-smm-hwmon.rst b/Documentation/hwmon/dell-smm-hwmon.rst > new file mode 100644 > index 000000000000..6e51de2c7dc3 > --- /dev/null > +++ b/Documentation/hwmon/dell-smm-hwmon.rst > @@ -0,0 +1,164 @@ > +.. SPDX-License-Identifier: GPL-2.0-or-later > + > +.. include:: <isonum.txt> > + > +Kernel driver dell-smm-hwmon > +============================ > + > +:Copyright: |copy| 2002-2005 Massimo Dal Zotto <dz@xxxxxxxxxx> > +:Copyright: |copy| 2019 Giovanni Mascellani <gio@xxxxxxxxxx> > + > +Description > +----------- > + > +On many Dell laptops the System Management Mode (SMM) BIOS can be > +queried for the status of fans and temperature sensors. Userspace > +utilities like ``sensors`` can be used to return the readings. The > +userspace suite `i8kutils`__ can also be used to read the sensors and > +automatically adjust fan speed (please notice that it currently uses > +the deprecated ``/proc/i8k`` interface). > + > + __ https://github.com/vitorafsr/i8kutils > + > +``sysfs`` interface > +------------------- > + > +Temperature sensors and fans can be queried and set via the standard > +``hwmon`` interface on ``sysfs``, under the directory > +``/sys/class/hwmon/hwmonX`` for some value of ``X`` (search for the > +``X`` such that ``/sys/class/hwmon/hwmonX/name`` has content > +``dell_smm``). A number of other attributes can be read or written: > + > +=============================== ======= ======================================= > +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 > + control (not supported on all laptops, > + see below for details). > +temp[1-10]_input RO Temperature reading in milli-degrees > + Celsius. > +temp[1-10]_label RO Temperature sensor label. > +=============================== ======= ======================================= > + > +Disabling automatic BIOS fan control > +------------------------------------ > + > +On some laptops the BIOS automatically sets fan speed every few > +seconds. Therefore the fan speed set by mean of this driver is quickly > +overwritten. > + > +There is experimental support for disabling automatic BIOS fan > +control, at least on laptops where the corresponding SMM command is > +known, by writing the value ``1`` in the attribute ``pwm1_enable`` > +(writing ``2`` enables automatic BIOS control again). Even if you have > +more than one fan, all of them are set to either enabled or disabled > +automatic fan control at the same time and, notwithstanding the name, > +``pwm1_enable`` sets automatic control for all fans. > + > +If ``pwm1_enable`` is not available, then it means that SMM codes for > +enabling and disabling automatic BIOS fan control are not whitelisted > +for your hardware. It is possible that codes that work for other > +laptops actually work for yours as well, or that you have to discover > +new codes. > + > +Check the list ``i8k_whitelist_fan_control`` in file > +``drivers/hwmon/dell-smm-hwmon.c`` in the kernel tree: as a first > +attempt you can try to add your machine and use an already-known code > +pair. If, after recompiling the kernel, you see that ``pwm1_enable`` > +is present and works (i.e., you can manually control the fan speed), > +then please submit your finding as a kernel patch, so that other users > +can benefit from it. Please see > +:ref:`Documentation/process/submitting-patches <submittingpatches>` > +for information on submitting patches. > + > +If no known code works on your machine, you need to resort to do some > +probing, because unfortunately Dell does not publish datasheets for > +its SMM. You can experiment with the code in `this repository`__ to > +probe the BIOS on your machine and discover the appropriate codes. > + > + __ https://github.com/clopez/dellfan/ > + > +Again, when you find new codes, we'd be happy to have your patches! > + > +Module parameters > +----------------- > + > +* force:bool > + Force loading without checking for supported > + models. (default: 0) > + > +* ignore_dmi:bool > + Continue probing hardware even if DMI data does not > + match. (default: 0) > + > +* restricted:bool > + Allow fan control only to processes with the > + ``CAP_SYS_ADMIN`` capability set or processes run > + as root when using the legacy ``/proc/i8k`` > + interface. In this case normal users will be able > + to read temperature and fan status but not to > + control the fan. If your notebook is shared with > + other users and you don't trust them you may want > + to use this option. (default: 1, only available > + with ``CONFIG_I8K``) > + > +* power_status:bool > + Report AC status in ``/proc/i8k``. (default: 0, > + only available with ``CONFIG_I8K``) > + > +* fan_mult:uint > + Factor to multiply fan speed with. (default: > + autodetect) > + > +* fan_max:uint > + Maximum configurable fan speed. (default: > + autodetect) > + > +Legacy ``/proc`` interface > +-------------------------- > + > +.. warning:: This interface is obsolete and deprecated and should not > + used in new applications. This interface is only > + available when kernel is compiled with option > + ``CONFIG_I8K``. > + > +The information provided by the kernel driver can be accessed by > +simply reading the ``/proc/i8k`` file. For example:: > + > + $ cat /proc/i8k > + 1.0 A17 2J59L02 52 2 1 8040 6420 1 2 > + > +The fields read from ``/proc/i8k`` are:: > + > + 1.0 A17 2J59L02 52 2 1 8040 6420 1 2 > + | | | | | | | | | | > + | | | | | | | | | +------- 10. buttons status > + | | | | | | | | +--------- 9. AC status > + | | | | | | | +-------------- 8. fan0 RPM > + | | | | | | +------------------- 7. fan1 RPM > + | | | | | +--------------------- 6. fan0 status > + | | | | +----------------------- 5. fan1 status > + | | | +-------------------------- 4. temp0 reading (Celsius) > + | | +---------------------------------- 3. Dell service tag (later known as 'serial number') > + | +-------------------------------------- 2. BIOS version > + +------------------------------------------ 1. /proc/i8k format version > + > +A negative value, for example -22, indicates that the BIOS doesn't > +return the corresponding information. This is normal on some > +models/BIOSes. > + > +For performance reasons the ``/proc/i8k`` doesn't report by default > +the AC status since this SMM call takes a long time to execute and is > +not really needed. If you want to see the ac status in ``/proc/i8k`` > +you must explictitly enable this option by passing the > +``power_status=1`` parameter to insmod. If AC status is not > +available -1 is printed instead. > + > +The driver provides also an ioctl interface which can be used to > +obtain the same information and to control the fan status. The ioctl > +interface can be accessed from C programs or from shell using the > +i8kctl utility. See the source file of ``i8kutils`` for more > +information on how to use the ioctl interface. > diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst > index 230ad59b462b..092435ad6bb8 100644 > --- a/Documentation/hwmon/index.rst > +++ b/Documentation/hwmon/index.rst > @@ -44,6 +44,7 @@ Hardware Monitoring Kernel Drivers > coretemp > da9052 > da9055 > + dell-smm-hwmon > dme1737 > ds1621 > ds620
