Re: [PATCH v1 3/3] usb: typec: displayport: Check cable altmode support

[Benson Leung]

On Thu, Jun 11, 2026 at 12:21:46PM +0000, Andrei Kuchynski wrote:
> Update the probe function to utilize the new
> typec_cable_altmode_unsupported() helper. If the cable doesn't support
> DisplayPort altmode, don't initialize altmode_ops and prevent altmode
> from being activated.
> A captive cable shouldn't be checked; it may not provide discoverable
> capability information, but it is inherently designed to support the
> device's requirements.
> 
Thanks for explaining clearly that this unsupported check only makes sense
when the port partner reports it has a receptacle.

> Signed-off-by: Andrei Kuchynski <akuchynski@xxxxxxxxxxxx>

Reviewed-by: Benson Leung <bleung@xxxxxxxxxxxx>

> ---
>  drivers/usb/typec/altmodes/displayport.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index 263a89c5f3243..5ee33a69b9cf7 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -790,7 +790,6 @@ int dp_altmode_probe(struct typec_altmode *alt)
>  	dp->alt = alt;
>  
>  	alt->desc = "DisplayPort";
> -	typec_altmode_set_ops(alt, &dp_altmode_ops);
>  
>  	if (plug) {
>  		plug->desc = "Displayport";
> @@ -811,6 +810,10 @@ int dp_altmode_probe(struct typec_altmode *alt)
>  	if (plug)
>  		typec_altmode_set_drvdata(plug, dp);
>  
> +	if ((alt->vdo & DP_CAP_RECEPTACLE) && typec_cable_altmode_unsupported(alt))
> +		return 0;
> +
> +	typec_altmode_set_ops(alt, &dp_altmode_ops);
>  	if (!alt->mode_selection) {
>  		dp->state = plug ? DP_STATE_ENTER_PRIME : DP_STATE_ENTER;
>  		schedule_work(&dp->work);
> -- 
> 2.54.0.1099.g489fc7bff1-goog
> 
>

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