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Message-ID: <8309c55b-110c-5123-f7bc-8a82bdbf5086@gmx.de>
Date: Tue, 15 Feb 2022 20:45:33 +0100
From: Armin Wolf <W_Armin@....de>
To: Pali Rohár <pali@...nel.org>
Cc: jdelvare@...e.com, linux@...ck-us.net, linux-hwmon@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] hwmon: (dell-smm) Allow for specifying fan control
method as module parameter
Am 15.02.22 um 20:19 schrieb Pali Rohár:
> On Tuesday 15 February 2022 20:11:07 Armin Wolf wrote:
>> Right now, the only way to test if setting manual/auto fan control works
>> is to edit and recompile the module, which may be too cumbersome for
>> the average user.
> There is also another way suitable for testing purposes which do not
> requires any kernel patch. Call iopl(3) syscall which changes I/O
> privilege level to 3 and which allows to poke I/O registers.
>
This is not possible under kernel lockdown/Secure Boot.
>> Allow for specifying the desired fan mode control method when loading
>> the module, but taint the kernel if so since there is the possibility
>> for strange side effects on non-whitelisted models.
>> Also update docs and kernel-parameters.txt accordingly.
>>
>> Tested on a Dell Inspiron 3505.
>>
>> Signed-off-by: Armin Wolf <W_Armin@....de>
>> ---
>> .../admin-guide/kernel-parameters.txt | 3 +++
>> Documentation/hwmon/dell-smm-hwmon.rst | 21 ++++++++++------
>> drivers/hwmon/dell-smm-hwmon.c | 25 +++++++++++++------
>> 3 files changed, 35 insertions(+), 14 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index d68053db21cc..4f1b6c2b7ed1 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -968,6 +968,9 @@
>> dell_smm_hwmon.fan_max=
>> [HW] Maximum configurable fan speed.
>>
>> + dell_smm_hwmon.fan_mode_method=
>> + [HW] Method to use for changing fan mode.
>> +
>> dfltcc= [HW,S390]
>> Format: { on | off | def_only | inf_only | always }
>> on: s390 zlib hardware support for compression on
>> diff --git a/Documentation/hwmon/dell-smm-hwmon.rst b/Documentation/hwmon/dell-smm-hwmon.rst
>> index beec88491171..564d99cda869 100644
>> --- a/Documentation/hwmon/dell-smm-hwmon.rst
>> +++ b/Documentation/hwmon/dell-smm-hwmon.rst
>> @@ -67,13 +67,16 @@ 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
>> +As a first step, you can load the module with the module parameter
>> +``fan_mode_method`` set to 1 to test if your hardware works with
>> +an already know method for disabling automatic BIOS fan control.
>> +If ``pwm1_enable`` is now 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.
>> +Just add your model to the list ``i8k_whitelist_fan_control`` in
>> +file ``drivers/hwmon/dell-smm-hwmon.c`` in the kernel tree and use
>> +the already known code pair.
>> +Please read
>> :ref:`Documentation/process/submitting-patches.rst <submittingpatches>`
>> for information on submitting patches.
>>
>> @@ -120,6 +123,10 @@ Module parameters
>> Maximum configurable fan speed. (default:
>> autodetect)
>>
>> +* fan_mode_method:uint
>> + Method to use for changing fan mode (default:
>> + from whitelist)
>> +
>> Legacy ``/proc`` interface
>> --------------------------
>>
>> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
>> index 9949eeb79378..1c4cc516c8b2 100644
>> --- a/drivers/hwmon/dell-smm-hwmon.c
>> +++ b/drivers/hwmon/dell-smm-hwmon.c
>> @@ -111,6 +111,10 @@ static uint fan_max;
>> module_param(fan_max, uint, 0);
>> MODULE_PARM_DESC(fan_max, "Maximum configurable fan speed (default: autodetect)");
>>
>> +static uint fan_mode_method;
>> +module_param_unsafe(fan_mode_method, uint, 0);
>> +MODULE_PARM_DESC(fan_mode_method, "Method to use for changing fan mode (default: from whitelist)");
> No, please really do not introduce another kernel parameter for this
> driver. There are already many and we do not need to extend this list.
>
>> +
>> struct smm_regs {
>> unsigned int eax;
>> unsigned int ebx;
>> @@ -677,7 +681,7 @@ static umode_t dell_smm_is_visible(const void *drvdata, enum hwmon_sensor_types
>>
>> break;
>> case hwmon_pwm_enable:
>> - if (data->auto_fan)
>> + if (data->auto_fan && data->manual_fan)
>> /*
>> * There is no command for retrieve the current status
>> * from BIOS, and userspace/firmware itself can change
>> @@ -1282,14 +1286,21 @@ static int __init dell_smm_probe(struct platform_device *pdev)
>> data->i8k_fan_max = fan_max ? : I8K_FAN_HIGH; /* Must not be 0 */
>> data->i8k_pwm_mult = DIV_ROUND_UP(255, data->i8k_fan_max);
>>
>> - fan_control = dmi_first_match(i8k_whitelist_fan_control);
>> - if (fan_control && fan_control->driver_data) {
>> - const struct i8k_fan_control_data *control = fan_control->driver_data;
>> + /* value specified via module param overrides whitelist */
>> + if (fan_mode_method > 0 && fan_mode_method <= ARRAY_SIZE(i8k_fan_control_data)) {
>> + data->manual_fan = i8k_fan_control_data[fan_mode_method - 1].manual_fan;
>> + data->auto_fan = i8k_fan_control_data[fan_mode_method - 1].auto_fan;
>> + } else {
>> + fan_control = dmi_first_match(i8k_whitelist_fan_control);
>> + if (fan_control && fan_control->driver_data) {
>> + const struct i8k_fan_control_data *control = fan_control->driver_data;
>>
>> - data->manual_fan = control->manual_fan;
>> - data->auto_fan = control->auto_fan;
>> - dev_info(&pdev->dev, "enabling support for setting automatic/manual fan control\n");
>> + data->manual_fan = control->manual_fan;
>> + data->auto_fan = control->auto_fan;
>> + }
>> }
>> + if (data->manual_fan && data->auto_fan)
>> + dev_info(&pdev->dev, "enabling support for setting automatic/manual fan control\n");
>>
>> if (!fan_mult) {
>> /*
>> --
>> 2.30.2
>>
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