Re: [PATCH RFC v2 06/20] drm: Introduce DRM_CLIENT_CAP_POST_BLEND_COLOR_PIPELINE

Thu, 11 Dec 2025 07:27:09 -0800 

Harry,

On 9/29/25 6:48 AM, Harry Wentland wrote:



On 2025-09-17 20:43, Nícolas F. R. A. Prado wrote:

Introduce DRM_CLIENT_CAP_POST_BLEND_COLOR_PIPELINE which a DRM client
can set to enable the usage of post-blend color pipelines instead of the
now deprecated CRTC color management properties: "GAMMA_LUT",
"DEGAMMA_LUT" and "CTM".

Signed-off-by: Nícolas F. R. A. Prado <[email protected]>
---
  drivers/gpu/drm/drm_atomic_uapi.c   | 15 +++++++++++++++
  drivers/gpu/drm/drm_connector.c     |  1 +
  drivers/gpu/drm/drm_crtc_internal.h |  1 +
  drivers/gpu/drm/drm_ioctl.c         |  9 +++++++++
  drivers/gpu/drm/drm_mode_object.c   |  9 +++++++++
  include/drm/drm_file.h              |  7 +++++++
  include/uapi/drm/drm.h              | 19 +++++++++++++++++++
  7 files changed, 61 insertions(+)


diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/ 
drm_atomic_uapi.c
index 
063c142fd9b656e228cfc660d005a3fbb4640d32..f5125fa3fa28ff2a6ff07fd7cf07d4bdf77ab738 100644

--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c

@@ -452,6 +452,11 @@ static int drm_atomic_crtc_set_property(struct 
drm_crtc *crtc,

      } else if (property == config->prop_vrr_enabled) {
          state->vrr_enabled = val;
      } else if (property == config->degamma_lut_property) {
+        if (file_priv->post_blend_color_pipeline) {
+            drm_dbg_atomic(dev,

+                "Setting DEGAMMA_LUT CRTC property not permitted with 
DRM_CLIENT_CAP_POST_BLEND_COLOR_PIPELINE client cap\n");

+            return -EINVAL;
+        }
          ret = drm_property_replace_blob_from_id(dev,
                      &state->degamma_lut,
                      val,

@@ -460,6 +465,11 @@ static int drm_atomic_crtc_set_property(struct 
drm_crtc *crtc,

          state->color_mgmt_changed |= replaced;
          return ret;
      } else if (property == config->ctm_property) {
+        if (file_priv->post_blend_color_pipeline) {
+            drm_dbg_atomic(dev,

+                "Setting CTM CRTC property not permitted with 
DRM_CLIENT_CAP_POST_BLEND_COLOR_PIPELINE client cap\n");

+            return -EINVAL;
+        }
          ret = drm_property_replace_blob_from_id(dev,
                      &state->ctm,
                      val,

@@ -468,6 +478,11 @@ static int drm_atomic_crtc_set_property(struct 
drm_crtc *crtc,

          state->color_mgmt_changed |= replaced;
          return ret;
      } else if (property == config->gamma_lut_property) {
+        if (file_priv->post_blend_color_pipeline) {
+            drm_dbg_atomic(dev,

+                "Setting GAMMA_LUT CRTC property not permitted with 
DRM_CLIENT_CAP_POST_BLEND_COLOR_PIPELINE client cap\n");

+            return -EINVAL;
+        }
          ret = drm_property_replace_blob_from_id(dev,
                      &state->gamma_lut,
                      val,

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/ 
drm_connector.c
index 
4d6dc9ebfdb5bc730b1aff7a184448af7b93f078..f58cfd2131139ff3e613adc4dbb9ddbedf724dc7 100644

--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c

@@ -3440,6 +3440,7 @@ int drm_mode_getconnector(struct drm_device 
*dev, void *data,

       */

      ret = drm_mode_object_get_properties(&connector->base, 
file_priv->atomic,

              file_priv->plane_color_pipeline,
+            file_priv->post_blend_color_pipeline,
              (uint32_t __user *)(unsigned long)(out_resp->props_ptr),

              (uint64_t __user *)(unsigned long)(out_resp- 
>prop_values_ptr),

              &out_resp->count_props);

diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/ 
drm_crtc_internal.h
index 
e3dbdcbfa385b940ec0b5476adde6146fe4afde1..c53f154e5392a10c326c844b7321666275f9ac02 100644

--- a/drivers/gpu/drm/drm_crtc_internal.h
+++ b/drivers/gpu/drm/drm_crtc_internal.h

@@ -169,6 +169,7 @@ void drm_mode_object_unregister(struct drm_device 
*dev,

                  struct drm_mode_object *object);

  int drm_mode_object_get_properties(struct drm_mode_object *obj, bool 
atomic,

                     bool plane_color_pipeline,
+                   bool post_blend_color_pipeline,
                     uint32_t __user *prop_ptr,
                     uint64_t __user *prop_values,
                     uint32_t *arg_count_props);
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c

index 
01592d10e3465ddceddef94bc417f98d3ec12087..ea9600f5392f520a2b42ba7ef363d2f08ce19812 100644

--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c

@@ -383,6 +383,15 @@ drm_setclientcap(struct drm_device *dev, void 
*data, struct drm_file *file_priv)

              return -EINVAL;
          file_priv->plane_color_pipeline = req->value;
          break;
+    case DRM_CLIENT_CAP_POST_BLEND_COLOR_PIPELINE:
+        if (!file_priv->atomic)
+            return -EINVAL;
+        if (req->value > 1)
+            return -EINVAL;

+        if (!drm_core_check_feature(dev, 
DRIVER_POST_BLEND_COLOR_PIPELINE))

+            return -EINVAL;
+        file_priv->post_blend_color_pipeline = req->value;
+        break;
      default:
          return -EINVAL;
      }

diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/ 
drm_mode_object.c
index 
b45d501b10c868c6d9b7a5a8760eadbd7b372a6a..5e6c3de9456b997985142a68b9cef57771a58bdc 100644

--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -388,6 +388,7 @@ EXPORT_SYMBOL(drm_object_property_get_default_value);
  /* helper for getconnector and getproperties ioctls */

  int drm_mode_object_get_properties(struct drm_mode_object *obj, bool 
atomic,

                     bool plane_color_pipeline,
+                   bool post_blend_color_pipeline,
                     uint32_t __user *prop_ptr,
                     uint64_t __user *prop_values,
                     uint32_t *arg_count_props)

@@ -416,6 +417,13 @@ int drm_mode_object_get_properties(struct 
drm_mode_object *obj, bool atomic,

                  continue;
          }

+        if (!post_blend_color_pipeline && obj->type == 
DRM_MODE_OBJECT_CRTC) {

+            struct drm_crtc *crtc = obj_to_crtc(obj);
+
+            if (prop == crtc->color_pipeline_property)
+                continue;
+        }
+
          if (*arg_count_props > count) {
              ret = __drm_object_property_get_value(obj, prop, &val);
              if (ret)

@@ -475,6 +483,7 @@ int drm_mode_obj_get_properties_ioctl(struct 
drm_device *dev, void *data,

      ret = drm_mode_object_get_properties(obj, file_priv->atomic,
              file_priv->plane_color_pipeline,
+            file_priv->post_blend_color_pipeline,
              (uint32_t __user *)(unsigned long)(arg->props_ptr),
              (uint64_t __user *)(unsigned long)(arg->prop_values_ptr),
              &arg->count_props);
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h

index 
1a3018e4a537b3341acb50187d47371f6b781b9d..42b9a43baa18079af8ec2ea5b1484b23c497beb0 100644

--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -213,6 +213,13 @@ struct drm_file {
       */
      bool plane_color_pipeline;
+    /**
+     * @post_blend_color_pipeline:
+     *
+     * True if client understands post-blend color pipelines
+     */
+    bool post_blend_color_pipeline;
+
      /**
       * @was_master:
       *
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h

index 
c6c53e57958e951204154ce41a69696a6876f0e8..f9ac10b3e4876f71005a87dedefa4aed320566f0 100644

--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -927,6 +927,25 @@ struct drm_get_cap {
   */
  #define DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE    7
+/**
+ * DRM_CLIENT_CAP_POST_BLEND_COLOR_PIPELINE


DRM_CLIENT_CAP_CRTC_COLOR_PIPELINE might be better to align
terminology between pre- and post-blend pipelines. It would
also make it clear that this is about the color pipeline on
a drm_crtc (which pretty much by definition means post-
blending).

Same answer here. Will be replacing s/post_blend/crtc in v3.

Thanks!

--
Ariel D'Alessandro
Software Engineer

Collabora Ltd.

Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK 
Registered in England & Wales, no. 5513718
















    











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