Re: [Intel-gfx] [PATCH] drm/i915/debugfs: HDCP capability enc NULL check

["Gupta, Anshuman" <anshuman.gupta@intel.com>]

> -----Original Message-----
> From: Nautiyal, Ankit K <ankit.k.nautiyal@intel.com>
> Sent: Monday, February 1, 2021 4:25 PM
> To: Gupta, Anshuman <anshuman.gupta@intel.com>; intel-
> gfx@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/debugfs: HDCP capability enc NULL
> check
> 
> 
> On 1/29/2021 1:30 PM, Anshuman Gupta wrote:
> > DP-MST connector encoder initializes at modeset Adding a
> > connector->encoder NULL check in order to avoid any NULL pointer
> > dereference.
> > intel_hdcp_enable() already handle this but debugfs can also invoke
> > the intel_{hdcp,hdcp2_capable}.
> > Handling it gracefully.
> >
> > Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
> > ---
> >   drivers/gpu/drm/i915/display/intel_hdcp.c | 14 ++++++++++++--
> >   1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c
> > b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > index ae1371c36a32..58af323d189a 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > @@ -135,11 +135,16 @@ int intel_hdcp_read_valid_bksv(struct
> intel_digital_port *dig_port,
> >   /* Is HDCP1.4 capable on Platform and Sink */
> >   bool intel_hdcp_capable(struct intel_connector *connector)
> >   {
> > -	struct intel_digital_port *dig_port =
> intel_attached_dig_port(connector);
> > +	struct intel_digital_port *dig_port;
> >   	const struct intel_hdcp_shim *shim = connector->hdcp.shim;
> >   	bool capable = false;
> >   	u8 bksv[5];
> >
> > +	if (!connector->encoder)
> > +		return -ENODEV;
> > +
> 
> For connector->encoder check, I feel the correct place should be in
> function:
> enc_to_dig_port(), where we should return if encoder is NULL in display_types.h
@Jani could you please provide your Ack, if enc_to_dig_port() is the correct place to do connector->encoder NULL check.
Br,
Anshuman Gupta.
> Currently we assume encoder is not NULL and try to check encoder->type, which
> might break in case of MST.
> With that change, we can simply check NULL check for 'dig_port', as
> intel_attached_dig_port(connector) might still return NULL.
> 
> Regards,
> Ankit
> 
> > +	dig_port = intel_attached_dig_port(connector);
> > +
> >   	if (!shim)
> >   		return capable;
> >
> > @@ -156,11 +161,16 @@ bool intel_hdcp_capable(struct intel_connector
> *connector)
> >   /* Is HDCP2.2 capable on Platform and Sink */
> >   bool intel_hdcp2_capable(struct intel_connector *connector)
> >   {
> > -	struct intel_digital_port *dig_port =
> intel_attached_dig_port(connector);
> > +	struct intel_digital_port *dig_port;
> >   	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> >   	struct intel_hdcp *hdcp = &connector->hdcp;
> >   	bool capable = false;
> >
> > +	if (!connector->encoder)
> > +		return -ENODEV;
> > +
> > +	dig_port = intel_attached_dig_port(connector);
> > +
> >   	/* I915 support for HDCP2.2 */
> >   	if (!hdcp->hdcp2_supported)
> >   		return false;
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