Re: [PATCH] drm/i915/display: Fix too few bits in transcoder mask variables

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Mon, Jul 13, 2026 at 09:56:26AM -0700, John Harrison wrote:
> New transcoder enum values (for CMTG) were recently added which pushed
> the maximum transcoder mask beyond 8bits. The patch in question
> updated the info structure's u8 to u16 but not any of the functions
> that process transcoder masks. So fix those as well.
> 
> Signed-off-by: John Harrison <John.Harrison@Igalia.com>
> Fixes: 789dda6429e0 ("drm/i915/cmtg: Add CMTG transcoder offset in struct _device_info")

Thanks for this finding. But could you please double check Sashiko?
We might have further gaps around this:
https://sashiko.dev/#/patchset/20260713165626.2827609-1-John.Harrison%40Igalia.com

> Cc: Uma Shankar <uma.shankar@intel.com>
> Cc: Animesh Manna <animesh.manna@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: intel-gfx@lists.freedesktop.org
> Cc: intel-xe@lists.freedesktop.org
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 22 ++++++++++----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 214454f419e9..38763a6802c5 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -3767,9 +3767,9 @@ static void enabled_joiner_pipes(struct intel_display *display,
>  	}
>  }
>  
> -static u8 hsw_panel_transcoders(struct intel_display *display)
> +static u16 hsw_panel_transcoders(struct intel_display *display)
>  {
> -	u8 panel_transcoder_mask = BIT(TRANSCODER_EDP);
> +	u16 panel_transcoder_mask = BIT(TRANSCODER_EDP);
>  
>  	if (DISPLAY_VER(display) >= 11)
>  		panel_transcoder_mask |= BIT(TRANSCODER_DSI_0) | BIT(TRANSCODER_DSI_1);
> @@ -3777,13 +3777,13 @@ static u8 hsw_panel_transcoders(struct intel_display *display)
>  	return panel_transcoder_mask;
>  }
>  
> -static u8 hsw_enabled_transcoders(struct intel_crtc *crtc)
> +static u16 hsw_enabled_transcoders(struct intel_crtc *crtc)
>  {
>  	struct intel_display *display = to_intel_display(crtc);
> -	u8 panel_transcoder_mask = hsw_panel_transcoders(display);
> +	u16 panel_transcoder_mask = hsw_panel_transcoders(display);
>  	enum transcoder cpu_transcoder;
>  	u8 primary_pipe, secondary_pipes;
> -	u8 enabled_transcoders = 0;
> +	u16 enabled_transcoders = 0;
>  
>  	/*
>  	 * XXX: Do intel_display_power_get_if_enabled before reading this (for
> @@ -3844,18 +3844,18 @@ static u8 hsw_enabled_transcoders(struct intel_crtc *crtc)
>  	return enabled_transcoders;
>  }
>  
> -static bool has_edp_transcoders(u8 enabled_transcoders)
> +static bool has_edp_transcoders(u16 enabled_transcoders)
>  {
>  	return enabled_transcoders & BIT(TRANSCODER_EDP);
>  }
>  
> -static bool has_dsi_transcoders(u8 enabled_transcoders)
> +static bool has_dsi_transcoders(u16 enabled_transcoders)
>  {
>  	return enabled_transcoders & (BIT(TRANSCODER_DSI_0) |
>  				      BIT(TRANSCODER_DSI_1));
>  }
>  
> -static bool has_pipe_transcoders(u8 enabled_transcoders)
> +static bool has_pipe_transcoders(u16 enabled_transcoders)
>  {
>  	return enabled_transcoders & ~(BIT(TRANSCODER_EDP) |
>  				       BIT(TRANSCODER_DSI_0) |
> @@ -3863,7 +3863,7 @@ static bool has_pipe_transcoders(u8 enabled_transcoders)
>  }
>  
>  static void assert_enabled_transcoders(struct intel_display *display,
> -				       u8 enabled_transcoders)
> +				       u16 enabled_transcoders)
>  {
>  	/* Only one type of transcoder please */
>  	drm_WARN_ON(display->drm,
> @@ -5880,7 +5880,7 @@ static int intel_atomic_check_crtcs(struct intel_atomic_state *state)
>  }
>  
>  static bool intel_cpu_transcoders_need_modeset(struct intel_atomic_state *state,
> -					       u8 transcoders)
> +					       u16 transcoders)
>  {
>  	const struct intel_crtc_state *new_crtc_state;
>  	struct intel_crtc *crtc;
> @@ -6516,7 +6516,7 @@ int intel_atomic_check(struct drm_device *dev,
>  		}
>  
>  		if (is_trans_port_sync_mode(new_crtc_state)) {
> -			u8 trans = new_crtc_state->sync_mode_slaves_mask;
> +			u16 trans = new_crtc_state->sync_mode_slaves_mask;
>  
>  			if (new_crtc_state->master_transcoder != INVALID_TRANSCODER)
>  				trans |= BIT(new_crtc_state->master_transcoder);
> -- 
> 2.43.0
>