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

Mon, 13 Jul 2026 16:29:01 -0700 

On 7/13/26 15:43, Rodrigo Vivi wrote:

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 <[email protected]>
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
I found it because writeback support stopped working after rebasing to the latest tip. Unravelling that found the instances below and got writeback working again. But yeah, it looks like there are a few more threads to unravel. 

John.



Cc: Uma Shankar <[email protected]>
Cc: Animesh Manna <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
  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

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