On Wed, Oct 18, 2023 at 08:34:09PM +0000, RD Babiera wrote:
> DisplayPort Alt Mode CTS test 10.3.8 states that both sides of the
> connection shall be compatible with one another such that the connection
> is not Source to Source or Sink to Sink.
>
> The DisplayPort driver currently checks for a compatible pin configuration
> that resolves into a source and sink combination. The CTS test is designed
> to send a Discover Modes message that has a compatible pin configuration
> but advertises the same port capability as the device; the current check
> fails this.
>
> Verify that the port and port partner resolve into a valid source and sink
> combination before checking for a compatible pin configuration.
>
> ---
> Changes since v1:
> * Fixed styling errors
> * Added DP_CAP_IS_UFP_D and DP_CAP_IS_DFP_D as macros to typec_dp.h
> ---
>
> Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: RD Babiera <rdbabiera@xxxxxxxxxx>
Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> drivers/usb/typec/altmodes/displayport.c | 5 +++++
> include/linux/usb/typec_dp.h | 2 ++
> 2 files changed, 7 insertions(+)
>
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index 718da02036d8..9c17955da570 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -578,6 +578,11 @@ int dp_altmode_probe(struct typec_altmode *alt)
>
> /* FIXME: Port can only be DFP_U. */
>
> + /* Make sure that the port and partner can resolve into source and sink */
> + if (!(DP_CAP_IS_DFP_D(port->vdo) && DP_CAP_IS_UFP_D(alt->vdo)) &&
> + !(DP_CAP_IS_UFP_D(port->vdo) && DP_CAP_IS_DFP_D(alt->vdo)))
> + return -ENODEV;
> +
> /* Make sure we have compatiple pin configurations */
> if (!(DP_CAP_PIN_ASSIGN_DFP_D(port->vdo) &
> DP_CAP_PIN_ASSIGN_UFP_D(alt->vdo)) &&
> diff --git a/include/linux/usb/typec_dp.h b/include/linux/usb/typec_dp.h
> index 1f358098522d..4e6c0479307f 100644
> --- a/include/linux/usb/typec_dp.h
> +++ b/include/linux/usb/typec_dp.h
> @@ -67,6 +67,8 @@ enum {
> #define DP_CAP_UFP_D 1
> #define DP_CAP_DFP_D 2
> #define DP_CAP_DFP_D_AND_UFP_D 3
> +#define DP_CAP_IS_UFP_D(_cap_) (!!(DP_CAP_CAPABILITY(_cap_) & DP_CAP_UFP_D))
> +#define DP_CAP_IS_DFP_D(_cap_) (!!(DP_CAP_CAPABILITY(_cap_) & DP_CAP_DFP_D))
> #define DP_CAP_DP_SIGNALLING(_cap_) (((_cap_) & GENMASK(5, 2)) >> 2)
> #define DP_CAP_SIGNALLING_HBR3 1
> #define DP_CAP_SIGNALLING_UHBR10 2
>
> base-commit: 5220d8b04a840fa09434072c866d032b163419e3
> --
> 2.42.0.655.g421f12c284-goog
--
heikki
