linux-kernel - Re: [PATCH] hwmon: (dell-smm) Extend fan support to 5 fans

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Message-ID: <85794882-64c2-4eec-ba40-82d534f01c3e@gmx.de>
Date: Sat, 10 Jan 2026 13:14:52 +0100
From: Armin Wolf <W_Armin@....de>
To: Andrew Mark <android606@...il.com>, pali@...nel.org
Cc: linux@...ck-us.net, linux-hwmon@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (dell-smm) Extend fan support to 5 fans

Am 10.01.26 um 04:47 schrieb Andrew Mark:

> Dell Precision Tower workstations have 5 fan connectors, but the
> driver was limited to 4 fans after commit dbcfcb239b3b ("hwmon:
> (dell-smm) Increment the number of fans").
>
> This patch increases DELL_SMM_NO_FANS to 5 and adds the necessary
> hwmon channel info for the fifth fan and its PWM control.
>
> Without this patch, the PCIe/GPU cooling fan (fan 5) is not
> controllable, which can lead to overheating on systems with
> high-power fanless GPUs that depend on chassis cooling.
>
> Also adds a DMI quirk for Precision Tower 5810 to provide accurate
> fan labels, as the BIOS reports generic types for these fans.
>
> Tested on Dell Precision Tower 5810 (BIOS A34) with all 5 fans
> responding correctly to PWM control.
>
> Fan mapping for Precision Tower 5810:
> - fan0: CPU heatsink
> - fan1: Second CPU (dual-CPU systems only)
> - fan2: Right DIMM bank
> - fan3: Left DIMM bank
> - fan4: PCIe/GPU cooling
>
> Signed-off-by: Andrew Mark <android606@...il.com>
> ---
>   drivers/hwmon/dell-smm-hwmon.c | 19 ++++++++++++++++++-
>   1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> index 6040a8940..b112e6fbc 100644
> --- a/drivers/hwmon/dell-smm-hwmon.c
> +++ b/drivers/hwmon/dell-smm-hwmon.c
> @@ -74,7 +74,7 @@
>   #define DELL_SMM_LEGACY_EXECUTE	0x1
>   
>   #define DELL_SMM_NO_TEMP	10
> -#define DELL_SMM_NO_FANS	4
> +#define DELL_SMM_NO_FANS	5
>   
>   /* limit fan multiplier to avoid overflow */
>   #define DELL_SMM_MAX_FAN_MULT (INT_MAX / U16_MAX)
> @@ -175,6 +175,14 @@ static const char * const docking_labels[] = {
>   	"Docking Other Fan",
>   };
>   
> +static const char * const precision_tower_5810_labels[] = {
> +	"CPU Fan",
> +	"CPU Fan 2",
> +	"Right DIMM Fan",
> +	"Left DIMM Fan",
> +	"PCIe Fan",
> +};

Hi,

please use sensors3.conf to label you fans. Otherwise this driver will quickly
almost exclusively consist of DMI quirks for such labels.

The other changes are fine.

Thanks,
Armin Wolf

> +
>   static inline const char __init *i8k_get_dmi_data(int field)
>   {
>   	const char *dmi_data = dmi_get_system_info(field);
> @@ -991,6 +999,12 @@ static const char *dell_smm_fan_label(struct dell_smm_data *data, int channel)
>   	if (type < 0)
>   		return ERR_PTR(type);
>   
> +	if (dmi_match(DMI_PRODUCT_NAME, "Precision Tower 5810")) {
> +		if (channel < ARRAY_SIZE(precision_tower_5810_labels))
> +			return precision_tower_5810_labels[channel];
> +		return "Unknown Fan";
> +	}
> +
>   	if (type & 0x10) {
>   		dock = true;
>   		type &= 0x0F;
> @@ -1129,12 +1143,15 @@ static const struct hwmon_channel_info * const dell_smm_info[] = {
>   			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MIN | HWMON_F_MAX |
>   			   HWMON_F_TARGET,
>   			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MIN | HWMON_F_MAX |
> +			   HWMON_F_TARGET,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MIN | HWMON_F_MAX |
>   			   HWMON_F_TARGET
>   			   ),
>   	HWMON_CHANNEL_INFO(pwm,
>   			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
>   			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
>   			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
> +			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
>   			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE
>   			   ),
>   	NULL