Re: [PATCH] drm/i915/display: Assert valid cpu_transcoder

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

On Mon, 26 Jan 2026, Jonathan Cavitt <jonathan.cavitt@intel.com> wrote:
> Static analysis issue:
>
> Bit operations are being performed using bit offsets computed from
> cpu_transcoder values, which may (albeit unlikely) be -1.  Assert this
> is not the case when relevant.
>
> Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c     | 8 +++++++-
>  drivers/gpu/drm/i915/display/intel_display.c | 5 +++++
>  drivers/gpu/drm/i915/display/intel_dp.c      | 3 +++
>  drivers/gpu/drm/i915/display/intel_dp_mst.c  | 3 +++
>  4 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index d8739e2bb004..ec947c415e5f 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -3876,7 +3876,8 @@ static void intel_ddi_set_idle_link_train(struct intel_dp *intel_dp,
>  static bool intel_ddi_is_audio_enabled(struct intel_display *display,
>  				       enum transcoder cpu_transcoder)
>  {
> -	if (cpu_transcoder == TRANSCODER_EDP)
> +	if (cpu_transcoder == TRANSCODER_EDP ||
> +	    drm_WARN_ON(display->drm, cpu_transcoder == INVALID_TRANSCODER))
>  		return false;
>  
>  	if (!intel_display_power_is_enabled(display, POWER_DOMAIN_AUDIO_MMIO))
> @@ -4611,6 +4612,8 @@ intel_ddi_port_sync_transcoders(const struct intel_crtc_state *ref_crtc_state,
>  		if (!crtcs_port_sync_compatible(ref_crtc_state,
>  						crtc_state))
>  			continue;
> +		if (drm_WARN_ON(display->drm, crtc_state->cpu_transcoder == INVALID_TRANSCODER))
> +			continue;
>  		transcoders |= BIT(crtc_state->cpu_transcoder);
>  	}
>  
> @@ -4649,6 +4652,9 @@ static int intel_ddi_compute_config_late(struct intel_encoder *encoder,
>  	else
>  		crtc_state->master_transcoder = ffs(port_sync_transcoders) - 1;
>  
> +	if (drm_WARN_ON(display->drm, crtc_state->cpu_transcoder == INVALID_TRANSCODER))
> +		return -EINVAL;
> +
>  	if (crtc_state->master_transcoder == crtc_state->cpu_transcoder) {
>  		crtc_state->master_transcoder = INVALID_TRANSCODER;
>  		crtc_state->sync_mode_slaves_mask =
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 7491e00e3858..c9d50240d813 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -5855,9 +5855,14 @@ static bool intel_cpu_transcoders_need_modeset(struct intel_atomic_state *state,
>  {
>  	const struct intel_crtc_state *new_crtc_state;
>  	struct intel_crtc *crtc;
> +	struct drm_device *drm;
>  	int i;
>  
> +	drm = to_intel_display(state)->drm;

Please don't add struct drm_device local variables in display code.

Add display, and use display->drm instead.

BR,
Jani.


> +
>  	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
> +		if (drm_WARN_ON(drm, new_crtc_state->cpu_transcoder == INVALID_TRANSCODER))
> +			continue;
>  		if (new_crtc_state->hw.enable &&
>  		    transcoders & BIT(new_crtc_state->cpu_transcoder) &&
>  		    intel_crtc_needs_modeset(new_crtc_state))
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 79fd3b8d8b25..402b22423ff2 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -6412,6 +6412,9 @@ static int intel_modeset_affected_transcoders(struct intel_atomic_state *state,
>  		if (!crtc_state->hw.enable)
>  			continue;
>  
> +		if (drm_WARN_ON(display->drm, crtc_state->cpu_transcoder == INVALID_TRANSCODER))
> +			continue;
> +
>  		if (!(transcoders & BIT(crtc_state->cpu_transcoder)))
>  			continue;
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 24f8e60df9ac..f6690130d1cb 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -741,6 +741,9 @@ intel_dp_mst_transcoder_mask(struct intel_atomic_state *state,
>  		if (!crtc_state->hw.active)
>  			continue;
>  
> +		if (drm_WARN_ON(display->drm, crtc_state->cpu_transcoder == INVALID_TRANSCODER))
> +			continue;
> +
>  		transcoders |= BIT(crtc_state->cpu_transcoder);
>  	}

-- 
Jani Nikula, Intel