Re: [RFC PATCH v1] platform/x86: thinkpad_acpi: Add parameter to suppress invalid thermal sensors

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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On Mon, 18 Aug 2025, Marc Burkhardt wrote:

> While moving an existing Icinga installation to a Lenovo P15 20SU I came
> across broken JSON output from a "sensors -Aj" command consumed by the

The commit message is not meant to be a history lesson about how the patch
came to be but to describe the problem seen and how patch is fixing it. 
Please try to state imperatively what is the problem, not "I did x" kind 
of sentences. E.g.,

"sensors -Aj" JSON output on Lenovo P15 20SU is broken because ...

Also try to avoid using "This patch" to start a sentence.

> Icinga check_lm_sensors plugin. After fiddling around trying to build a
> fix in either lm_sensors or Icinga I found out the error was rooted in
> some sysfs file that was created but threw errors while being read. On my
> Lenovo ThinkPad the default fallback to 8 temperature sensors creates
> sysfs entries like in my case "temp8_input" that fail when read, causing
> the issue in user-space.
>
> This patch adds a module parameter (suppress_sensor) using
> module_param_array() to allow users to specify a comma-separated list of
> zero-based sensor indices to suppress sysfs file creation (e.g.
> suppress_sensor=3,7). Instead of a model-specific quirk, this provides
> flexible configuration for any ThinkPad with similar issues and is working
> out-of-the-box without additional models being marked for the quirk.

Can't we determine this at probe time automatically?

We generally try to avoid module parameters whenever possible. Sometimes,
if not automated way exists, quirk + a parameter intended for temporary 
use might be acceptable compromise. I don't understand why you say 
"additional models being marked for the quirk" as that seems never 
necessary even if a quirk exists.

> The
> parameter uses a fixed-size array based on TPACPI_MAX_THERMAL_SENSORS (16)
> consistent with the driver’s thermal sensor handling (ie.
> ibm_thermal_sensors_struct or sensor_dev_attr_thermal_temp_input).
> 
> Logging via pr_info() reports the number of suppressed sensors at module
> initialization, and pr_info() logs each suppressed sensor during sysfs
> attribute creation. Invalid sensor indices are logged once via pr_warn()
> to avoid repetitive warnings.

This logging likely needs work too (to print much less), but lets first 
agree with the way forward.

> Tested on a ThinkPad P15 with
> suppress_sensor=3,7, confirming suppression of temp4_input and temp8_input
> with no sysfs errors. Bounds checking for uncommon values is in place or
> will be logged.
> 
> The patch applies to the current
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git although
> it was initially written for a 6.16.0 kernel.
>
> I look forward to any feedback on the patch and/or handling of submission.
> Please CC: for now as I am not (yet) subscribed. Thank you.

Please don't include details like these 2 last paragraphs into the commit 
message itself, it's fine to state things like this below --- line as 
they're automatically removed when the patch is applied.

Usually Linus' tree is fine as base, but sometimes pdx86 for-next has 
diverged.

> 
> Signed-off-by: Marc Burkhardt <marc.burkhardt@protoco.consulting>
> ---
> Notes:
> I haven't posted on LKML or send a patch for over a decade now so
> please forgive any possible mistakes I made regarding current coding
> conventions or more generally in submitting this patch. The patch was
> running for some time here with faulty sensors removed from sysfs and no
> problems otherwise detected and was surely run through checkpatch.pl before
> submission. get_maintainer.pl was helpful to find the hopefully right
> people for CC:ing but I am otherweise totally unaware of any current
> procedures or best-practices when it comes to submitting a patch.

Welcome back. You did quite well regardless. :-)

> drivers/platform/x86/lenovo/thinkpad_acpi.c | 35 +++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
> index cc19fe520ea9..30ff01f87403 100644
> --- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
> +++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
> @@ -6019,6 +6019,30 @@ struct ibm_thermal_sensors_struct {
>  	s32 temp[TPACPI_MAX_THERMAL_SENSORS];
>  };
>  
> +static int suppress_sensor[TPACPI_MAX_THERMAL_SENSORS];
> +static unsigned int suppress_sensor_count;
> +
> +static bool is_sensor_suppressed(int index)
> +{
> +	unsigned int i;
> +	bool logged = false;
> +
> +	for (i = 0; i < suppress_sensor_count; i++) {
> +		if (suppress_sensor[i] == index)
> +			return true;
> +
> +		if (!logged &&
> +			(suppress_sensor[i] < 0
> +				|| suppress_sensor[i] >= TPACPI_MAX_THERMAL_SENSORS)) {
> +			pr_warn("Invalid sensor index %d in suppress_sensor\n",
> +				suppress_sensor[i]);
> +			logged = true;
> +		}
> +	}
> +
> +	return false;
> +}
> +
>  static const struct tpacpi_quirk thermal_quirk_table[] __initconst = {
>  	/* Non-standard address for thermal registers on some ThinkPads */
>  	TPACPI_Q_LNV3('R', '1', 'F', true),	/* L13 Yoga Gen 2 */
> @@ -6313,6 +6337,11 @@ static umode_t thermal_attr_is_visible(struct kobject *kobj,
>  
>  	int idx = sensor_attr->index;
>  
> +	if (is_sensor_suppressed(idx)) {
> +		pr_info("Sensor %d suppressed\n", idx);
> +		return 0;
> +	}
> +
>  	switch (thermal_read_mode) {
>  	case TPACPI_THERMAL_NONE:
>  		return 0;
> @@ -11653,6 +11682,9 @@ static void __init thinkpad_acpi_init_banner(void)
>  			thinkpad_id.model_str,
>  			(thinkpad_id.nummodel_str) ?
>  				thinkpad_id.nummodel_str : "unknown");
> +
> +	pr_info("Suppressing %d user-supplied sensor(s) via parameter suppress_sensor\n",
> +		suppress_sensor_count);
>  }
>  
>  /* Module init, exit, parameters */
> @@ -11785,6 +11817,9 @@ MODULE_PARM_DESC(experimental,
>  module_param_named(debug, dbg_level, uint, 0);
>  MODULE_PARM_DESC(debug, "Sets debug level bit-mask");
>  
> +module_param_array(suppress_sensor, int, &suppress_sensor_count, 0444);
> +MODULE_PARM_DESC(suppress_sensor, "Comma-separated sensor indices to suppress (e.g., 3,7)");
> +
>  module_param(force_load, bool, 0444);
>  MODULE_PARM_DESC(force_load,
>  		 "Attempts to load the driver even on a mis-identified ThinkPad when true");
> 

-- 
 i.