Re: [PATCH 1/2] bus: mhi: host: Add debug port personality switching

[Jeff Hugo <jeff.hugo@oss.qualcomm.com>]

On 11/13/2026 5:23 AM, Hongxing Xu wrote:
> diff --git a/Documentation/ABI/stable/sysfs-bus-mhi b/Documentation/ABI/stable/sysfs-bus-mhi
> index 8b9698f..1fe8510 100644
> --- a/Documentation/ABI/stable/sysfs-bus-mhi
> +++ b/Documentation/ABI/stable/sysfs-bus-mhi
> @@ -30,6 +30,20 @@ Description:	Initiates a SoC reset on the MHI controller.  A SoC reset is
>                   non-responsive, or as a means of loading new firmware as a
>                   system administration task.
>   
> +What:           /sys/bus/mhi/devices/.../debug_ports
> +Date:           November 2026
> +KernelVersion:  7.5
> +Contact:        mhi@lists.linux.dev
> +Description:    Controls which set of ports the MHI controller enumerates.
> +                Writing 0 selects the commercial personality, in which the
> +                channels that are only useful for debugging are not
> +                enumerated. Writing 1 selects the debug personality and
> +                additionally enumerates those channels, so that the extra
> +                WWAN ports appear, e.g. one for the diagnostic interface.
> +                Reading returns the currently active personality.
> +                Controllers that do not describe any debug-only channel are
> +                unaffected by this attribute.
> +

Why sysfs and not debugfs?

>   /**
> @@ -381,6 +384,16 @@ struct mhi_controller_config {
>    * @no_m3: Device doesn't support M3 state
>    * @irq_flags: irq flags passed to request_irq (optional)
>    * @mru: the default MRU for the MHI device
> + * @debug_ports: Whether the debug port personality is active, i.e. whether the
> + *		 channels marked with debug_only are enumerated. Controlled
> + *		 from userspace through the debug_ports sysfs attribute and
> + *		 applied by debug_ports_work. Zero-initialised, so a
> + *		 controller starts in the commercial personality.
> + * @debug_ports_pending: Latest personality requested from userspace, applied
> + *		 by debug_ports_work
> + * @debug_ports_work: Applies @debug_ports_pending from the ordered high
> + *		      priority workqueue, so the device creation it performs
> + *		      cannot race with a state transition

Are these optional?