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

Jani Nikula
2026-01-26T13:21:38Z

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>

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

> ---
> 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