linux-kernel - Re: [PATCH v5 2/7] dt-bindings: wireless: ieee80211: Add disable-rfkill property

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Message-ID: <c29de60c-c7c6-45d7-8d90-616df23df01c@kernel.org>
Date: Mon, 22 Dec 2025 11:23:18 +0100
From: Hans de Goede <hansg@...nel.org>
To: Bryan O'Donoghue <bod.linux@...w.ie>, jerome.debretagne@...il.com,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Johannes Berg <johannes@...solutions.net>,
 Lorenzo Bianconi <lorenzo@...nel.org>,
 Maximilian Luz <luzmaximilian@...il.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Jeff Johnson <jjohnson@...nel.org>, Manivannan Sadhasivam <mani@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
 platform-driver-x86@...r.kernel.org, ath12k@...ts.infradead.org,
 Jeff Johnson <jeff.johnson@....qualcomm.com>, Dale Whinham <daleyo@...il.com>
Subject: Re: [PATCH v5 2/7] dt-bindings: wireless: ieee80211: Add
 disable-rfkill property

+Cc Mani

Hi,

On 20-Dec-25 07:04, Bryan O'Donoghue wrote:
> On 20/12/2025 00:21, Jérôme de Bretagne via B4 Relay wrote:
>> From: Jérôme de Bretagne <jerome.debretagne@...il.com>
>>
>> For some devices, Wi-Fi is entirely hard blocked by default making
>> the Wi-Fi radio unusable, except if rfkill is disabled as expected
>> on those models.
>>
>> Commit c6a7c0b09d5f ("wifi: ath12k: Add Support for enabling or
>> disabling specific features based on ACPI bitflag") added a way to
>> support features set via ACPI, including the DISABLE_RFKILL bit.
>>
>> Add a disable-rfkill property to expose the DISABLE_RFKILL bit
>> equivalent for devices described by a Devicetree instead of ACPI.
>>
>> Signed-off-by: Jérôme de Bretagne <jerome.debretagne@...il.com>
>> ---
>>   Documentation/devicetree/bindings/net/wireless/ieee80211.yaml | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/net/wireless/ieee80211.yaml b/Documentation/devicetree/bindings/net/wireless/ieee80211.yaml
>> index d89f7a3f88a71d45d6f4ab2ae909eae09cbcaf9a..c10a4675640be947cd0b5eaec2c7ff367fd93945 100644
>> --- a/Documentation/devicetree/bindings/net/wireless/ieee80211.yaml
>> +++ b/Documentation/devicetree/bindings/net/wireless/ieee80211.yaml
>> @@ -29,6 +29,12 @@ properties:
>>         different 5 GHz subbands. Using them incorrectly could not work or
>>         decrease performance noticeably
>>
>> +  disable-rfkill:
>> +    type: boolean
>> +    description:
>> +      Disable rfkill for some devices on which Wi-Fi would be entirely hard
>> +      blocked by default otherwise
>> +
>>   additionalProperties: true
>>
>>   examples:
>>
>> -- 
>> 2.47.3
>>
>>
>>
> 
> Is this really a hardware description though ?

I would say yes it is. The wifi chip has an rfkill input pin and
things will be broken when that pin is hardwired to a fixed value
rather then being actually connected to a GPIO from say
the embedded controller.

So I think that we would need here is not a disable-rfkill property
but some way to indicate in the DT-node that the rfkill input pin
is not connected and thus should be ignored.

This (the rfkill input pin being not-connected) IMHO very much
is hw-description.

Also see the
"[PATCH 0/9] Add support for handling PCIe M.2 Key E connectors in devicetree"
series and then specifically:

https://lore.kernel.org/platform-driver-x86/20251112-pci-m2-e-v1-7-97413d6bf824@oss.qualcomm.com/

Which adds:

+  w_disable1-gpios:
+    description: GPIO controlled connection to W_DISABLE1# signal. This signal
+      is used by the system to disable WiFi radio in the M.2 card. Refer, PCI
+      Express M.2 Specification r4.0, sec 3.1.12.3 for more details.
+    maxItems: 1

What if there is no such GPIO, because the W_DISABLE1# signal is hardwired
in a specific implementation of the M.2 slot ?

In that case we will also need some way to propagate that info to the wifi
driver, having some sort of generic devicetree property for wifi-cards
which can be injected as a software-node property in the PCI-device being
instantiated for the WIFI card to let the driver no not to honor to
W_DISABLE1# signal will be useful here too and this is as hardware-description
as hardware-description can get.

So how about: "w_disable1-not-connected" + "w_disable2-not-connected" boolean
properties in a generic WIFI devicetree binding and also use that here?

> I think this logic belongs in drivers/net/wireless/ath/ath12k/ triggering on a compat string.

See above, I do not believe that abusing compat-strings for this is the way
to go.

Regards,

Hans