Re: [PATCH v2] drm/i915/display: PORT_NONE is not valid

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 23 Jan 2026, Jonathan Cavitt <jonathan.cavitt@intel.com> wrote:
> Static analysis issue:
>
> In assert_port_valid, add a check to ensure port != PORT_NONE, as that
> is not a valid port.  The check must be explicit to prevent a bad bit
> shift operation in the general case via short-circuiting.  It's not
> likely this will ever come up in a real use case, but it's at least
> worth guarding against.
>
> It would probably also be pertinent to modify the behavior of the
> port_name function to correctly print PORT_NONE in this case, as
> currently the port would be reported as 'port @' by the debugger.  But
> that should be done separately, and given port_name is mostly just a
> debug printing helper function anyways, fixing it is a low priority.
>
> v2:
> - Conditional check was backwards.  Fix it.  (Jani)
>
> Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>

Thanks for the patch, pushed to drm-intel-next.

BR,
Jani.


> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 7491e00e3858..0c3bb3f98ee4 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -7828,7 +7828,8 @@ static bool intel_ddi_crt_present(struct intel_display *display)
>  
>  bool assert_port_valid(struct intel_display *display, enum port port)
>  {
> -	return !drm_WARN(display->drm, !(DISPLAY_RUNTIME_INFO(display)->port_mask & BIT(port)),
> +	return !drm_WARN(display->drm,
> +			 !(port >= 0 && DISPLAY_RUNTIME_INFO(display)->port_mask & BIT(port)),
>  			 "Platform does not support port %c\n", port_name(port));
>  }

-- 
Jani Nikula, Intel