Re: [PATCH RFC v3 02/10] usb: misc: qcom_eud: add sysfs attribute for port selection

[Konrad Dybcio]

On 3/11/26 2:16 PM, Greg Kroah-Hartman wrote:
> On Mon, Mar 09, 2026 at 01:33:29PM -0700, Elson Serrao wrote:
>> EUD can be mapped to either the primary USB port or the secondary USB port
>> depending on the value of the EUD_PORT_SEL register. Add a 'port' sysfs
>> attribute to allow userspace to select which port EUD should operate on
>> and update the ABI documentation. This is needed for systems with dual
>> USB ports where EUD needs to be accessible on either port depending on the
>> system configuration and use case.
>>
>> Signed-off-by: Elson Serrao <elson.serrao@xxxxxxxxxxxxxxxx>
>> ---
>>  Documentation/ABI/testing/sysfs-driver-eud | 16 ++++++++
>>  drivers/usb/misc/qcom_eud.c                | 43 ++++++++++++++++++++++
>>  2 files changed, 59 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-driver-eud b/Documentation/ABI/testing/sysfs-driver-eud
>> index 2bab0db2d2f0..67223f73ee60 100644
>> --- a/Documentation/ABI/testing/sysfs-driver-eud
>> +++ b/Documentation/ABI/testing/sysfs-driver-eud
>> @@ -7,3 +7,19 @@ Description:
>>  		EUD based on a 1 or a 0 value. By enabling EUD,
>>  		the user is able to activate the mini-usb hub of
>>  		EUD for debug and trace capabilities.
>> +
>> +What:		/sys/bus/platform/drivers/qcom_eud/.../port
>> +Date:		January 2026
>> +Contact:	Elson Serrao <elson.serrao@xxxxxxxxxxxxxxxx>
>> +Description:
>> +		Selects which USB port the Embedded USB Debugger (EUD)
>> +		is mapped to on platforms providing multiple High-Speed
>> +		USB ports.
>> +
>> +		Valid values:
>> +		  0 - Primary USB port
>> +		  1 - Secondary USB port
> 
> Why not use "primary" and "secondary" as values instead?  That makes
> this much simpler to understand.

It's not inconceivable that future iterations of this hardware will let
one mux between more than two USB PHYs/ports (there are already a multitude
of SoCs where we have 4 or more USB controllers and >= that ports)

Konrad