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

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Date:   Wed,  8 Feb 2023 20:53:19 +0000
From:   Prashant Malani <pmalani@...omium.org>
To:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     bleung@...omium.org, Prashant Malani <pmalani@...omium.org>,
        stable@...r.kernel.org, Diana Zigterman <dzigterman@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guillaume Ranquet <granquet@...libre.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Macpaul Lin <macpaul.lin@...iatek.com>,
        Pablo Sun <pablo.sun@...iatek.com>
Subject: [PATCH] usb: typec: altmodes/displayport: Fix probe pin assign check

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>
---

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