On Tue, Apr 23, 2024 at 7:06 PM Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> wrote: > > 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. So originally on my system, I didn't have the displayport driver config enabled. My expectation was that the alt-mode would show up but would not be controllable (like all other alt-modes without drivers). What ends up happening is that no alt-mode shows up and trying to enable the trace crashes. When the displayport support isn't there, I think it should just be enumerated as a normal, unsupported alt-mode. > > > + 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