linux-kernel - Re: [PATCH] usb: typec: altmodes/displayport: Fix probe pin assign check

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Message-ID: <Y+YG2DIHy/vg0vxY@kuha.fi.intel.com>
Date:   Fri, 10 Feb 2023 10:56:56 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Prashant Malani <pmalani@...omium.org>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        bleung@...omium.org, stable@...r.kernel.org,
        Diana Zigterman <dzigterman@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guillaume Ranquet <granquet@...libre.com>,
        Macpaul Lin <macpaul.lin@...iatek.com>,
        Pablo Sun <pablo.sun@...iatek.com>
Subject: Re: [PATCH] usb: typec: altmodes/displayport: Fix probe pin assign
 check

On Wed, Feb 08, 2023 at 08:53:19PM +0000, Prashant Malani wrote:
> While checking Pin Assignments of the port and partner during probe, we
> don't take into account whether the peripheral is a plug or receptacle.
> 
> This manifests itself in a mode entry failure on certain docks and
> dongles with captive cables. For instance, the Startech.com Type-C to DP
> dongle (Model #CDP2DP) advertises its DP VDO as 0x405. This would fail
> the Pin Assignment compatibility check, despite it supporting
> Pin Assignment C as a UFP.
> 
> Update the check to use the correct DP Pin Assign macros that
> take the peripheral's receptacle bit into account.
> 
> Fixes: c1e5c2f0cb8a ("usb: typec: altmodes/displayport: correct pin assignment for UFP receptacles")
> Cc: stable@...r.kernel.org
> Reported-by: Diana Zigterman <dzigterman@...omium.org>
> Signed-off-by: Prashant Malani <pmalani@...omium.org>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
> 
> I realize this is a bit late in the release cycle, but figured since it
> is a fix it might still be considered. Please let me know if it's too
> late and I can re-send this after the 6.3-rc1 is released. Thanks!
> 
>  drivers/usb/typec/altmodes/displayport.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index 20db51471c98..662cd043b50e 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -547,10 +547,10 @@ int dp_altmode_probe(struct typec_altmode *alt)
>  	/* FIXME: Port can only be DFP_U. */
>  
>  	/* Make sure we have compatiple pin configurations */
> -	if (!(DP_CAP_DFP_D_PIN_ASSIGN(port->vdo) &
> -	      DP_CAP_UFP_D_PIN_ASSIGN(alt->vdo)) &&
> -	    !(DP_CAP_UFP_D_PIN_ASSIGN(port->vdo) &
> -	      DP_CAP_DFP_D_PIN_ASSIGN(alt->vdo)))
> +	if (!(DP_CAP_PIN_ASSIGN_DFP_D(port->vdo) &
> +	      DP_CAP_PIN_ASSIGN_UFP_D(alt->vdo)) &&
> +	    !(DP_CAP_PIN_ASSIGN_UFP_D(port->vdo) &
> +	      DP_CAP_PIN_ASSIGN_DFP_D(alt->vdo)))
>  		return -ENODEV;
>  
>  	ret = sysfs_create_group(&alt->dev.kobj, &dp_altmode_group);
> -- 
> 2.39.1.519.gcb327c4b5f-goog

thanks,

-- 
heikki