On Wed, 24 Apr 2024 at 04:48, Jameson Thies <jthies@xxxxxxxxxx> wrote:
>
> From: Abhishek Pandit-Subedi <abhishekpandit@xxxxxxxxxxxx>
>
> ucsi_register_altmode checks IS_ERR on returned pointer and treats
> NULL as valid. This results in a null deref when
> trace_ucsi_register_altmode is called. Return an error from
> ucsi_register_displayport when it is not supported and register the
> altmode with typec_port_register_altmode.
>
> Reviewed-by: Jameson Thies <jthies@xxxxxxxxxx>
> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@xxxxxxxxxxxx>
> ---
> Changes in V2:
> - Checks for error response from ucsi_register_displayport when
> registering DisplayPort alternate mode.
>
> drivers/usb/typec/ucsi/ucsi.c | 3 +++
> drivers/usb/typec/ucsi/ucsi.h | 2 +-
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index cb52e7b0a2c5c..f3b413f94fd28 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -361,6 +361,9 @@ static int ucsi_register_altmode(struct ucsi_connector *con,
> switch (desc->svid) {
> case USB_TYPEC_DP_SID:
> alt = ucsi_register_displayport(con, override, i, desc);
> + if (IS_ERR(alt) && PTR_ERR(alt) == -EOPNOTSUPP)
This makes it ignore EOPNOTSUPP if it is returned by the non-stub
implementation. I think the current state is actually better than the
implementation found in this patch. I'd suggest adding a comment to
ucsi_register_displayport() stub instead.
> + alt = typec_port_register_altmode(con->port, desc);
> +
> break;
> case USB_TYPEC_NVIDIA_VLINK_SID:
> if (desc->vdo == USB_TYPEC_NVIDIA_VLINK_DBG_VDO)
> diff --git a/drivers/usb/typec/ucsi/ucsi.h b/drivers/usb/typec/ucsi/ucsi.h
> index c4d103db9d0f8..c663dce0659ee 100644
> --- a/drivers/usb/typec/ucsi/ucsi.h
> +++ b/drivers/usb/typec/ucsi/ucsi.h
> @@ -496,7 +496,7 @@ ucsi_register_displayport(struct ucsi_connector *con,
> bool override, int offset,
> struct typec_altmode_desc *desc)
> {
> - return NULL;
> + return ERR_PTR(-EOPNOTSUPP);
> }
>
> static inline void
> --
> 2.44.0.769.g3c40516874-goog
>
--
With best wishes
Dmitry
